MedWorm.com provides a medical RSS filtering service. Over 6000 RSS medical sources are combined and output via different filters. This feed contains the latest items from the 'JARO - Journal of the Association for Research in Otolaryngology' source. Wed, 08 Feb 2012 15:44:33 +0100 http://www.medworm.com/index.php?rid=5667798&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F0r74m064h1456883%2F Abstract  We use analysis of a realistic three-dimensional finite-element model of the tunnel of Corti (ToC) in the middle turn of the gerbil cochlea tuned to the characteristic frequency (CF) of 4 kHz to show that the anatomical structure of the organ of Corti (OC) is consistent with the hypothesis that the cochlear amplifier functions as a fluid pump. The experimental evidence for the fluid pump is that outer hair cell (OHC) contraction and expansion induce oscillatory flow in the ToC. We show that this oscillatory flow can produce a fluid wave traveling in the ToC and that the outer pillar cells (OPC) do not present a significant barrier to fluid flow into the ToC. The wavelength of the resulting fluid wave launched into the tunnel at the CF is 1.5 mm, which is... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5667798 Fri, 03 Feb 2012 07:21:27 +0100 5667798 http://www.medworm.com/index.php?rid=5667799&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ft52823557745r954%2F Abstract  The voltage-gated potassium channel subunit Kv1.1 encoded by the Kcna1 gene is expressed in many brainstem nuclei, and electrophysiological studies of Kcna1-null mutant (−/−) single neurons suggest that channels containing this subunit are critical for precise processing of rapid acoustic perturbations. We tested the hypothesis that brief offsets of a background noise are behaviorally less salient for Kcna1 −/− mice, measured by changes in noise offset inhibition of acoustic startle reflexes (ASR). In experiment 1, noise offset was followed by ASR-eliciting sound bursts either after 1–10 ms quiet intervals or after the return of noise for 10–290 ms following 10-ms quiet gaps. ASR inhibition to offset and gaps was initially higher in +/+ mice bu... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5667799 Thu, 02 Feb 2012 18:14:10 +0100 5667799 http://www.medworm.com/index.php?rid=5648886&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F2432874381020223%2F Abstract  The medial olivocochlear reflex (MOCR) has been hypothesized to provide benefit for listening in noise. Strong physiological support for an anti-masking role for the MOCR has come from the observation that auditory nerve (AN) fibers exhibit reduced firing to sustained noise and increased sensitivity to tones when the MOCR is elicited. The present study extended a well-established computational model for normal-hearing and hearing-impaired AN responses to demonstrate that these anti-masking effects can be accounted for by reducing outer hair cell (OHC) gain, which is a primary effect of the MOCR. Tone responses in noise were examined systematically as a function of tone level, noise level, and OHC gain. Signal detection theory was used to predict detection and disc... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5648886 Fri, 27 Jan 2012 17:53:55 +0100 5648886 http://www.medworm.com/index.php?rid=5598479&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fa7367p75022j68p4%2F Abstract  Detection and localization of a target sound in the presence of concurrent, spatially distributed masking sounds is one of the most challenging tasks for the mammalian auditory system. Previous studies demonstrated that the ability to localize signals is decreased by interfering noise. In order to directly compare the behavioral performance in a signal processing task in noise between gerbils and humans in the free sound field, we quantified their localization ability for a low-frequency signal in the presence of six masking noise sources surrounding the subject. Thresholds were measured both for masking noises that were correlated or uncorrelated across the masking sources. Overall, the gerbils required a higher signal/noise ratio to detect the low-frequency sign... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5598479 Sat, 14 Jan 2012 06:54:54 +0100 5598479 http://www.medworm.com/index.php?rid=5582945&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fmt0n4660t5568070%2F Abstract  Synaptic transmission between the cochlear hair cell and its afferent fiber is mediated by glutamate receptors. While kainate receptors are known to be present in the spiral ganglion, little is known of their distribution or functional role. We have detected all five kainate receptor subunits in the mouse cochlea with quantitative RT-PCR and with immunohistochemistry. We observed kainate receptors on afferent terminals co-localized with α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (ampa) receptors at the afferent synapse. Individual terminals innervating a single hair cell varied in their ratios of ampa to kainate receptor immunoreactivity. Infusion of the mouse cochlea via the scala tympani with UBP296, a recently developed antagonist with high specificity... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5582945 Tue, 10 Jan 2012 06:48:38 +0100 5582945 http://www.medworm.com/index.php?rid=5505830&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fa4wg6073640q403n%2F Abstract  Genetic tools available for the mouse make it a powerful model to study the modulation of cochlear function by descending control systems. Suppression of distortion product otoacoustic emission (DPOAE) amplitude by contralateral acoustic stimulation (CAS) provides a robust tool for noninvasively monitoring the strength of descending modulation, yet investigations in mice have been performed infrequently and only under anesthesia, a condition likely to reduce olivocochlear activation. Here, we characterize the contralateral olivocochlear reflex in the alert, unanesthetized mouse. Head-fixed mice were restrained between two closed acoustic systems, while an artifact rejection protocol minimized contamination from self-generated sounds and movements. In mice anesthet... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5505830 Mon, 12 Dec 2011 17:13:26 +0100 5505830 http://www.medworm.com/index.php?rid=5505829&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fj58r486503171762%2F This study further examined the effect of formant-frequency variation on intelligibility by manipulating the rate of formant-frequency change. Target sentences were synthetic three-formant (F1 + F2 + F3) analogues of natural utterances. Perceptual organization was probed by presenting stimuli dichotically (F1 + F2C + F3C; F2 + F3), where F2C + F3C constitute a competitor for F2 and F3 that listeners must reject to optimize recognition. Competitors were derived using formant-frequency contours extracted from extended passages spoken by the same talker and processed to alter the rate of formant-frequency variation, such that rate scale factors relative to the target sentences were 0, 0.25, 0.5, 1, 2, and 4 (0 = constant frequencies). Competitor amplitude con... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5505829 Mon, 12 Dec 2011 17:13:26 +0100 5505829 http://www.medworm.com/index.php?rid=5505831&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fg2142p50306l4706%2F Abstract  The lateral superior olive (LSO) is a brainstem nucleus that is classically understood to encode binaural information in high-frequency sounds. Previous studies have shown that LSO cells are sensitive to envelope interaural time difference in sinusoidally amplitude-modulated (SAM) tones (Joris and Yin, J Neurophysiol 73:1043–1062, 1995; Joris, J Neurophysiol 76:2137–2156, 1996) and that a subpopulation of LSO neurons exhibit low-threshold potassium currents mediated by Kv1 channels (Barnes-Davies et al., Eur J Neurosci 19:325–333, 2004). It has also been shown that in many LSO cells the average response rate to ipsilateral SAM tones decreases with modulation frequency above a few hundred Hertz (Joris and Yin, J Neurophysiol 79:253–269, 1998). This low-pass f... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5505831 Mon, 12 Dec 2011 17:13:24 +0100 5505831 http://www.medworm.com/index.php?rid=5495229&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ft346278148p38562%2F Abstract  When a pure tone or low-numbered harmonic is presented to a listener, the resulting travelling wave in the cochlea slows down at the portion of the basilar membrane (BM) tuned to the input frequency due to the filtering properties of the BM. This slowing is reflected in the phase of the response of neurons across the auditory nerve (AN) array. It has been suggested that the auditory system exploits these across-channel timing differences to encode the pitch of both pure tones and resolved harmonics in complex tones. Here, we report a quantitative analysis of previously published data on the response of guinea pig AN fibres, of a range of characteristic frequencies, to pure tones of different frequencies and levels. We conclude that although the use of across-chann... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5495229 Thu, 08 Dec 2011 07:19:27 +0100 5495229 http://www.medworm.com/index.php?rid=5487688&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fj47226m487m5n552%2F Abstract  Hypothyroidism is a cause of genetic and environmentally induced deafness. The sensitivity of cochlear development and function to thyroid hormone (TH) mandates understanding TH action in this sensory organ. Prop1 df and Pou1f1 dw mutant mice carry mutations in different pituitary transcription factors, each resulting in pituitary thyrotropin deficiency. Despite the same lack of detectable serum TH, these mutants have very different hearing abilities: Prop1 df mutants are mildly affected, while Pou1f1 dw mutants are completely deaf. Genetic studies show that this difference is attributable to the genetic backgrounds. Using embryo transfer, we discovered that factors intrinsic to the fetus are the major contributor to this difference, not maternal eff... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5487688 Mon, 05 Dec 2011 17:41:27 +0100 5487688 http://www.medworm.com/index.php?rid=5469502&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fv057102x5443w615%2F Abstract  Epidemiologic studies of hearing loss in adults have demonstrated that the odds of hearing loss are substantially lower in black than in white individuals. The basis of this association is unknown. We hypothesized that skin pigmentation as a marker of melanocytic functioning mediates this observed association and that skin pigmentation is associated with hearing loss independent of race/ethnicity. We analyzed cross-sectional data from 1,258 adults (20–59 years) in the 2003–2004 cycle of the National Health and Nutritional Examination Survey who had assessment of Fitzpatrick skin type and pure-tone audiometric testing. Audiometric thresholds in the worse hearing ear were used to calculate speech- (0.5–4 kHz) and high-frequency (3–8 kHz) pure-t... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5469502 Tue, 29 Nov 2011 22:22:09 +0100 5469502 http://www.medworm.com/index.php?rid=5469501&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fdpl50h8180284307%2F Abstract  Using whole-cell patch-clamp recordings, we measured changes in membrane capacitance (ΔC m) in two subsets of hair cells from the leopard frog amphibian papilla (AP): the low-frequency (100–500 Hz), rostral hair cells and the high-frequency (500–1200 Hz), caudal hair cells, in order to investigate tonotopic differences in exocytosis. Depolarizations of both rostral and caudal hair cells evoked robust ΔC m responses of similar amplitude. However, the calcium dependence of release, i.e., the relationship between ΔC m relative to the amount of calcium influx (Q Ca2+), was found to be linear in rostral hair cells but supra-linear in caudal hair cells. In addition, the higher numbers of vesicles released at caudal hair cell active zones suggests incre... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5469501 Tue, 29 Nov 2011 22:22:09 +0100 5469501 http://www.medworm.com/index.php?rid=5469503&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fl72x564338184560%2F Abstract  Past studies have explored the relative strengths of auditory features in a selective attention task by pitting features against one another and asking listeners to report the words perceived in a given sentence. While these studies show that the continuity of competing features affects streaming, they did not address whether the influence of specific features is modulated by volitionally directed attention. Here, we explored whether the continuity of a task-irrelevant feature affects the ability to selectively report one of two competing speech streams when attention is specifically directed to a different feature. Sequences of simultaneous pairs of spoken digits were presented in which exactly one digit of each pair matched a primer phrase in pitch and exactly o... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5469503 Tue, 29 Nov 2011 22:22:08 +0100 5469503 http://www.medworm.com/index.php?rid=5469504&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F43086r77r838p5n1%2F Abstract  Interaural time differences (ITDs) can be used to localize sounds in the horizontal plane. ITDs can be extracted from either the fine structure of low-frequency sounds or from the envelopes of high-frequency sounds. Studies of the latter have included stimuli with periodic envelopes like amplitude-modulated tones or transposed stimuli, and high-pass filtered Gaussian noises. Here, four experiments are presented investigating the perceptual relevance of ITD cues in synthetic and recorded “rustling” sounds. Both share the broad long-term power spectrum with Gaussian noise but provide more pronounced envelope fluctuations than Gaussian noise, quantified by an increased waveform fourth moment, W. The current data show that the JNDs in ITD for band-pass rustling sou... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5469504 Tue, 29 Nov 2011 22:22:06 +0100 5469504 http://www.medworm.com/index.php?rid=5422761&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fq8206925005v7164%2F Abstract  Neurotrophins prevent spiral ganglion neuron (SGN) degeneration in animal models of ototoxin-induced deafness and may be used in the future to improve the hearing of cochlear implant patients. It is increasingly common for patients with residual hearing to undergo cochlear implantation. However, the effect of neurotrophin treatment on acoustic hearing is not known. In this study, brain-derived neurotrophic factor (BDNF) was applied to the round window membrane of adult guinea pigs for 4 weeks using a cannula attached to a mini-osmotic pump. SGN survival was first assessed in ototoxically deafened guinea pigs to establish that the delivery method was effective. Increased survival of SGNs was observed in the basal and middle cochlear turns of deafened guinea pi... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5422761 Wed, 16 Nov 2011 06:49:19 +0100 5422761 http://www.medworm.com/index.php?rid=5348575&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fu8phu543940n5820%2F Abstract  Using a scanning laser interferometer, we recently measured the volume velocity of the basilar membrane vibration in the sensitive gerbil cochlea and estimated that the cochlear power gain is ~100 at low sound pressure levels (Ren et al., Nat Commun 2:216–223, 2011a). We thank Shera et al. for recognizing the technical challenges of our experiments and appreciating the beauty of our data in their comment (Shera et al., J Assoc Res Otolaryngol (in press), 2011). These authors argue that our analysis is inappropriate, invalidating our conclusion; moreover, they suggest that our finding of a power gain of >1 could arise from a passive structure or cochlea. While our analysis and interpretation remain to be verified, they are justified according to commonly accept... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5348575 Fri, 21 Oct 2011 05:48:19 +0100 5348575 http://www.medworm.com/index.php?rid=5324465&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Flw76867421414563%2F Abstract  Stimulus-frequency otoacoustic emissions (SFOAEs) have been used to study a variety of topics in cochlear mechanics, although a current topic of debate is where in the cochlea these emissions are generated. One hypothesis is that SFOAE generation is predominately near the peak region of the traveling wave. An opposing hypothesis is that SFOAE generation near the peak region is deemphasized compared to generation in the tail region of the traveling wave. A comparison was made between the effect of low-frequency biasing on both SFOAEs and a physiologic measure that arises from the peak region of the traveling wave—the compound action potential (CAP). SFOAE biasing was measured as the amplitude of spectral sidebands from varying bias tone levels. CAP biasing was me... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5324465 Sat, 15 Oct 2011 05:48:07 +0100 5324465 http://www.medworm.com/index.php?rid=5324466&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F4j282965542h6k1j%2F Abstract  A novel psychophysical method was developed for assessing spatial resolution in cochlear implants. Spectrally flat and spectrally peaked pulse train stimuli were generated by interleaving pulses on 11 electrodes. Spectrally flat stimuli used loudness-balanced currents and the spectrally peaked stimuli had a single spatial ripple with the current of the middle electrode raised to create a peak while the currents on two electrodes equally spaced at variable distance from the peak electrode were reduced to create valleys. The currents on peak and valley electrodes were adjusted to balance the overall loudness with the spectrally flat stimulus, while keeping the currents on flanking electrodes fixed. The psychometric functions obtained from percent correct discriminat... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5324466 Sat, 15 Oct 2011 05:48:06 +0100 5324466 http://www.medworm.com/index.php?rid=5297511&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fh571462817047v88%2F Abstract  Animal experiments suggest that chronic tinnitus (“ringing in the ears”) may result from processes that overcompensate for lost afferent input. Abnormally elevated spontaneous neural activity has been found in the dorsal cochlear nucleus (DCN) of animals with psychophysical evidence of tinnitus. However, it has also been reported that DCN ablation fails to reduce established tinnitus. Since other auditory areas have been implicated in tinnitus, the role of the DCN is unresolved. The apparently conflicting electrophysiological and lesion data can be reconciled if the DCN serves as a necessary trigger zone rather than a chronic generator of tinnitus. The present experiment used lesion procedures identical to those that failed to decrease pre-existing tinnitus. T... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5297511 Tue, 04 Oct 2011 05:54:12 +0100 5297511 http://www.medworm.com/index.php?rid=5297510&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F237q022kn2v75324%2F Abstract  Cochlear implant listeners receive auditory stimulation through amplitude-modulated electric pulse trains. Auditory nerve studies in animals demonstrate qualitatively different patterns of firing elicited by low versus high pulse rates, suggesting that stimulus pulse rate might influence the transmission of temporal information through the auditory pathway. We tested in awake guinea pigs the temporal acuity of auditory cortical neurons for gaps in cochlear implant pulse trains. Consistent with results using anesthetized conditions, temporal acuity improved with increasing pulse rates. Unlike the anesthetized condition, however, cortical neurons responded in the awake state to multiple distinct features of the gap-containing pulse trains, with the dominant features... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5297510 Tue, 04 Oct 2011 05:54:12 +0100 5297510 http://www.medworm.com/index.php?rid=5286333&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F953873w468433463%2F Abstract  The auditory system is capable of robust recognition of sounds in the presence of competing maskers (e.g., other voices or background music). This capability arises despite the fact that masking stimuli can disrupt neural responses at the cortical level. Since the origins of such interference effects remain unknown, in this study, we work to identify and quantify neural interference effects that originate due to masking occurring within and outside receptive fields of neurons. We record from single and multi-unit auditory sites from field L, the auditory cortex homologue in zebra finches. We use a novel method called spike timing-based stimulus filtering that uses the measured response of each neuron to create an individualized stimulus set. In contrast to previou... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5286333 Sat, 01 Oct 2011 05:46:49 +0100 5286333 http://www.medworm.com/index.php?rid=5274579&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F244824u27078t463%2F Abstract  In their article, “Measurement of cochlear power gain in the sensitive gerbil ear,” Ren et al. (Nat Commun 2:216, 2011) claim to provide “the first direct experimental evidence of power amplification in the sensitive living cochlea.” While we recognize the technical challenges of the experiments and appreciate the beauty of the data, the authors’ analysis and interpretation of the measurements are invalid. We review the concept of impedance (i.e., the ratio of pressure to velocity) as it applies to cochlear mechanics and show that Ren et al. mistakenly equate the impedances near the basilar membrane and stapes with the impedance characteristic of an infinite, uniform tube of fluid. As a consequence of this error, Ren et al.’s measurements and analysis p... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5274579 Tue, 27 Sep 2011 05:54:24 +0100 5274579 http://www.medworm.com/index.php?rid=5251314&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fhl3233108435h874%2F Abstract  Psychophysical methods provide a mechanism to infer the characteristics of basilar membrane responses in humans that cannot be directly measured. Because these behavioral measures are indirect, the interpretation of results depends on several underlying assumptions. Ongoing uncertainty about the suitability of these assumptions and the most appropriate measurement and compression estimation procedures, and unanswered questions regarding the effects of cochlear hearing loss and age on basilar membrane nonlinearities, motivated this experiment. Here, estimates of cochlear nonlinearities using temporal masking curves (TMCs) were obtained in a large sample of adults of various ages whose hearing ranged from normal to moderate cochlear hearing loss (Experiment 1). A wi... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5251314 Thu, 22 Sep 2011 06:38:13 +0100 5251314 http://www.medworm.com/index.php?rid=5251315&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fh1083897588u8324%2F Abstract  Diverse cellular and environmental stresses can activate the heat shock response, an evolutionarily conserved mechanism to protect proteins from denaturation. Stressors activate heat shock transcription factor 1 (HSF1), which binds to heat shock elements in the genes for heat shock proteins, leading to rapid induction of these important molecular chaperones. Both heat and noise stress are known to activate the heat shock response in the cochlea and protect it from subsequent noise trauma. However, the contribution of HSF1 to induction of heat shock proteins following noise trauma has not been investigated at the molecular level. We evaluated the role of HSF1 in the cochlea following noise stress by examining induction of heat shock proteins in Hsf1 +/− contr... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5251315 Tue, 20 Sep 2011 05:50:33 +0100 5251315 http://www.medworm.com/index.php?rid=5184698&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F1jl6047v8nk2278t%2F Abstract  Aminoglycoside ototoxicity involves the accumulation of antibiotic molecules in the inner ear hair cells and the subsequent degeneration of these cells. The exact route of entry of aminoglycosides into the hair cells in vivo is still unknown. Similar to other small organic cations, aminoglycosides could be brought into the cell by endocytosis or permeate through large non-selective cation channels, such as mechanotransduction channels or ATP-gated P2X channels. Here, we show that the aminoglycoside antibiotic gentamicin can enter mouse outer hair cells (OHCs) via TRPA1, non-selective cation channels activated by certain pungent compounds and by endogenous products of lipid peroxidation. Using conventional and perforated whole-cell patch clamp recordings, we found t... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5184698 Wed, 31 Aug 2011 05:52:57 +0100 5184698 http://www.medworm.com/index.php?rid=5162841&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F65216052m5217777%2F Abstract  The inner ear arises from multipotent placodal precursors that are gradually committed to the otic fate and further differentiate into all inner ear cell types, with the exception of a few immigrating neural crest-derived cells. The otocyst plays a pivotal role during inner ear development: otic progenitor cells sub-compartmentalize into non-sensory and prosensory domains, giving rise to individual vestibular and auditory organs and their associated ganglia. The genes and pathways underlying this progressive subdivision and differentiation process are not entirely known. The goal of this study was to identify a comprehensive set of genes expressed in the chicken otocyst using the serial analysis of gene expression (SAGE) method. Our analysis revealed several hundr... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5162841 Fri, 19 Aug 2011 06:42:27 +0100 5162841 http://www.medworm.com/index.php?rid=5132730&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F11h07051675t6m7h%2F Abstract  It has been reported that normal-hearing Chinese speakers base their lexical tone recognition on fine structure regardless of temporal envelope cues. However, a few psychoacoustic and perceptual studies have demonstrated that listeners with sensorineural hearing impairment may have an impaired ability to use fine structure information, whereas their ability to use temporal envelope information is close to normal. The purpose of this study is to investigate the relative contributions of temporal envelope and fine structure cues to lexical tone recognition in normal-hearing and hearing-impaired native Mandarin Chinese speakers. Twenty-two normal-hearing subjects and 31 subjects with various degrees of sensorineural hearing loss participated in the study. Sixteen set... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5132730 Thu, 11 Aug 2011 06:03:23 +0100 5132730 http://www.medworm.com/index.php?rid=5120289&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fg52g327t29l145n8%2F Abstract  The frequency following response (FFR), a scalp-recorded measure of phase-locked brainstem activity, is often assumed to reflect the pitch of sounds as perceived by humans. In two experiments, we investigated the characteristics of the FFR evoked by complex tones. FFR waveforms to alternating-polarity stimuli were averaged for each polarity and added, to enhance envelope, or subtracted, to enhance temporal fine structure information. In experiment 1, frequency-shifted complex tones, with all harmonics shifted by the same amount in Hertz, were presented diotically. Only the autocorrelation functions (ACFs) of the subtraction-FFR waveforms showed a peak at a delay shifted in the direction of the expected pitch shifts. This expected pitch shift was also present in th... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5120289 Mon, 08 Aug 2011 19:56:09 +0100 5120289 http://www.medworm.com/index.php?rid=5064156&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F2x14173056h4158m%2F Abstract  In the present study, genotype–phenotype correlations in eight Dutch DFNB8/10 families with compound heterozygous mutations in TMPRSS3 were addressed. We compared the phenotypes of the families by focusing on the mutation data. The compound heterozygous variants in the TMPRSS3 gene in the present families included one novel variant, p.Val199Met, and four previously described pathogenic variants, p.Ala306Thr, p.Thr70fs, p.Ala138Glu, and p.Cys107Xfs. In addition, the p.Ala426Thr variant, which had previously been reported as a possible polymorphism, was found in one family. All affected family members reported progressive bilateral hearing impairment, with variable onset ages and progression rates. In general, the hearing impairment affected the high frequencies fi... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5064156 Sat, 23 Jul 2011 05:52:45 +0100 5064156 http://www.medworm.com/index.php?rid=5064157&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F3286833053812638%2F Abstract  Although intratympanic (IT) administration of drugs has gained wide clinical acceptance, the distribution of drugs in the inner ear following IT administration is not well established. Gadolinium (Gd) has been previously used as a marker in conjunction with magnetic resonance imaging (MRI) to visualize distribution in inner ear fluids in a qualitative manner. In the present study, we applied gadolinium chelated with diethylenetriamine penta-acetic acid (Gd-DTPA) to the round window niche of 12 guinea pigs using SeprapackTM (carboxlmethylcellulose-hyaluronic acid) pledgets which stabilized the fluid volume in the round window niche. Gd-DTPA distribution was monitored sequentially with time following application. Distribution in normal, unperforated ears was compared... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5064157 Tue, 19 Jul 2011 06:42:40 +0100 5064157 http://www.medworm.com/index.php?rid=5031114&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F2623q576345x6725%2F Abstract  In order to improve realism in middle ear (ME) finite-element modeling (FEM), comprehensive and precise morphological data are needed. To date, micro-scale X-ray computed tomography (μCT) recordings have been used as geometric input data for FEM models of the ME ossicles. Previously, attempts were made to obtain these data on ME soft tissue structures as well. However, due to low X-ray absorption of soft tissue, quality of these images is limited. Another popular approach is using histological sections as data for 3D models, delivering high in-plane resolution for the sections, but the technique is destructive in nature and registration of the sections is difficult. We combine data from high-resolution μCT recordings with data from high-resolution orthogonal-pla... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5031114 Wed, 13 Jul 2011 06:02:33 +0100 5031114 http://www.medworm.com/index.php?rid=5031115&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fp12m3g5307805125%2F Abstract  In cases of acquired sensorineural hearing loss, death of cochlear neurons is thought to arise largely as a result of sensory-cell loss. However, recent studies of acoustic overexposure report massive degeneration of the cochlear nerve despite complete hair cell survival (Kujawa and Liberman, J Neurosci 29:14077–14085, 2009). To assess the primary loss of spiral ganglion cells (SGCs) in human ears, neuronal counts were performed in 100 temporal bones from 100 individuals, aged newborn to 100 years, selected to include only cases with a normal population of inner and outer hair cells. Ganglion cell counts declined at a mean rate of 100 cells per year of life. There were no significant gender or inter-aural differences, and a slight increase in degeneration in... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5031115 Tue, 12 Jul 2011 05:58:20 +0100 5031115 http://www.medworm.com/index.php?rid=5010425&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ft23xt082161v2u54%2F Abstract  Inner ear hair cell loss is the most common pathology seen after ototoxic drug injury. While certain drugs such as aminoglycosides and cisplatin are well-known to have dramatic ototoxic effects, it is probable that there are other drugs that cause occult degrees of hair cell loss and lesser degrees of hearing loss. Anti-cancer drugs are particularly strong candidates due to their general cytotoxicity. We have screened a library of 88 anti-cancer drugs (National Cancer Institute Approved Oncology Drugs Set) for drugs that damage hair cells of the zebrafish lateral line. The screen identified four out of five known ototoxic drugs. The screen also identified four out of seven suspected ototoxic drugs (drugs that have isolated case reports of patients developing heari... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=5010425 Wed, 06 Jul 2011 05:57:01 +0100 5010425 http://www.medworm.com/index.php?rid=4999771&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F70p516364w222501%2F Abstract  The acoustic basis of auditory spatial acuity was investigated in CBA/129 mice by relating patterns of behavioral errors to directional features of the head-related transfer function (HRTF). Behavioral performance was assessed by training the mice to lick a water spout during sound presentations from a “safe” location and to suppress the response during presentations from “warning” locations. Minimum audible angles (MAAs) were determined by delivering the safe and warning sounds from different locations in the inter-aural horizontal and median vertical planes. HRTFs were measured at the same locations by implanting a miniature microphone and recording the gain of sound energy near the ear drum relative to free field. Mice produced an average MAA of 31° wh... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4999771 Thu, 30 Jun 2011 06:11:33 +0100 4999771 http://www.medworm.com/index.php?rid=4961925&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fy34656t321201713%2F Abstract  Recent work in mouse showed that acoustic overexposure can produce a rapid and irreversible loss of cochlear nerve peripheral terminals on inner hair cells (IHCs) and a slow degeneration of spiral ganglion cells, despite full recovery of cochlear thresholds and no loss of inner or outer hair cells (Kujawa and Liberman, J Neurosci 29:14077–14085, 2009). This contrasts with earlier ultrastructural work in guinea pig suggesting that acute noise-induced neural degeneration is followed by full regeneration of cochlear nerve terminals in the IHC area (Puel et al., Neuroreport 9:2109–2114, 1998; Pujol and Puel, Ann N Y Acad Sci 884:249–254, 1999). Here, we show that the same patterns of primary neural degeneration reported for mouse are also seen in the noise-exposed ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4961925 Mon, 20 Jun 2011 14:15:25 +0100 4961925 http://www.medworm.com/index.php?rid=4946828&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fhv40735h42643654%2F Abstract  Premature birth is a well-known risk factor for sensorineural hearing loss in general and auditory neuropathy in particular. However, relatively little is known about the underlying causes, in part because there are so few relevant histopathological studies. Here, we report on the analysis of hair cell loss patterns in 54 temporal bones from premature infants and a control group of 46 bones from full-term infants, all of whom spent time in the neonatal intensive care unit at the Hospital de Niños in San Jose, Costa Rica, between 1977 and 1993. The prevalence of significant hair cell loss was higher in the preterm group than the full-term group (41% vs. 28%, respectively). The most striking finding was the frequency of selective inner hair cell loss, an extremely ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4946828 Wed, 15 Jun 2011 05:49:44 +0100 4946828 http://www.medworm.com/index.php?rid=4938352&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F9282k753u04322hm%2F Abstract  Tinnitus, the perception of a sound without an external acoustic source, is a complex perceptual phenomenon affecting the quality of life in 17% of the adult population. Despite its ubiquity and morbidity, the pathophysiology of tinnitus is a work in progress, and there is no generally accepted cure or treatment. Development of a reliable common animal model is crucial for tinnitus research and may advance this field. The goal of this study was to develop a tinnitus mouse model. Tinnitus was induced in an experimental group of mice by an exposure to a loud (116 dB sound pressure level (SPL)) narrow band noise (one octave, centered at 16 kHz) during 1 h under anesthesia. The tinnitus was then assessed behaviorally by measuring gap induced suppression... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4938352 Sat, 11 Jun 2011 06:03:55 +0100 4938352 http://www.medworm.com/index.php?rid=4938353&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fy38w46p081315525%2F Abstract  Previous work suggests that bilateral cochlear implant users are sensitive to interaural cues if experimental speech processors are used to preserve accurate interaural information in the electrical stimulation pattern. Binaural unmasking occurs in adults and children when an interaural delay is applied to the envelope of a high-rate pulse train. Nevertheless, for speech perception, binaural unmasking benefits have not been demonstrated consistently, even with coordinated stimulation at both ears. The present study aimed at bridging the gap between basic psychophysical performance on binaural signal detection tasks on the one hand and binaural perception of speech in noise on the other hand. Therefore, binaural signal detection was expanded to multi-channel stimul... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4938353 Thu, 09 Jun 2011 05:46:40 +0100 4938353 http://www.medworm.com/index.php?rid=4896088&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fq206456m68w7444j%2F This study aimed to characterize the vibration-induced vestibulo-ocular reflex (ViVOR) in VSCD. ViVORs in one PCD and 17 SCD patients, confirmed by CT imaging reformatted in semicircular canal planes, were measured with dual-search coils as binocular three-dimensional eye rotations induced by skull vibrations from a bone oscillator (B71—10 ohms) at 7 ms, 500 Hz, 135-dB peak-force level (re: 1 μN). The ViVOR eye rotation axes were computed by vector analysis and referenced to known semicircular canal planes. Onset latency of the ViVOR was 11 ms. ViVOR from VSCD was up to nine times greater than normal. The ViVOR’s torsional rotation was always contraversive-torsional (the eye’s upper pole rotated away from the stimulated ear), i.e. its direction was clockwis... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4896088 Wed, 01 Jun 2011 06:00:38 +0100 4896088 http://www.medworm.com/index.php?rid=4896089&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fq5n5026n12435308%2F Abstract  Basilar membrane (BM) motion and auditory nerve fiber (ANF) tuning are generally very similar, but the ANF had appeared to be unresponsive to a plateau mode of BM motion that occurs at frequencies above an ANF’s characteristic frequency (CF). We recorded ANF responses from the gerbil, concentrating on this supra-CF region. We observed a supra-CF plateau in ANF responses at high stimulus level, indicating that the plateau mode of BM motion can be excitatory. Content Type Journal ArticlePages 1-17DOI 10.1007/s10162-011-0272-5Authors Stanley Huang, Department of Biomedical Engineering, Columbia University, 351 Engineering Terrace, Mail Code 8904 1210 Amsterdam Avenue, New York, NY 10027, USAElizabeth S. Olson, Department of Biomedical Engineering, Columbia Univ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4896089 Fri, 27 May 2011 17:48:52 +0100 4896089 http://www.medworm.com/index.php?rid=4896090&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F23113u325514h156%2F Abstract  Decades of clinical and basic research in visual system development have shown that degraded or imbalanced visual inputs can induce a long-lasting visual impairment called amblyopia. In the auditory domain, it is well established that inducing a conductive hearing loss (CHL) in young laboratory animals is associated with a panoply of central auditory system irregularities, ranging from cellular morphology to behavior. Human auditory deprivation, in the form of otitis media (OM), is tremendously common in young children, yet the evidence linking a history of OM to long-lasting auditory processing impairments has been equivocal for decades. Here, we review the apparent discrepancies in the clinical and basic auditory literature and provide a meta-analysis to show th... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4896090 Tue, 24 May 2011 05:53:08 +0100 4896090 http://www.medworm.com/index.php?rid=4854766&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ff524058260v82668%2F Abstract  Studies using inbred strains of mice have been invaluable for identifying alleles that adversely affect hearing. However, the efficacy of those studies is limited by the phenotypes that these strains express and the alleles that they segregate. Here, by selectively breeding phenotypically and genetically heterogeneous NIH Swiss mice, we generated two lines—the all-frequency hearing loss (AFHL) line and the high-frequency hearing loss (HFHL) line—with differential hearing loss. The AFHL line exhibited characteristics typical of severe, early-onset, sensorineural hearing impairment. In contrast, the HFHL line expressed a novel early-onset, mildly progressive, and frequency-specific sensorineural hearing loss. By quantitative trait loci (QTLs) analyses in these t... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4854766 Wed, 18 May 2011 18:17:16 +0100 4854766 http://www.medworm.com/index.php?rid=4832383&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fp5746l75p8u1364q%2F Abstract  The tectorial membrane (TM) connects to the stereociliary bundles of outer hair cells (OHCs). Humans with an autosomal dominant C1509G mutation in alpha-tectorin, a protein constituent of the TM, are born with a partial hearing loss that worsens over time. The Tecta C1509/+ transgenic mouse with the same point mutation has partial hearing loss secondary to a shortened TM that only contacts the first row of OHCs. As well, Tecta C1509G/+ mice have increased expression of the OHC electromotility protein, prestin. We sought to determine whether these changes impact OHC survival. Distortion product otoacoustic emission thresholds in a quiet environment did not change to 6 months of age. However, noise exposure produced acute threshold shifts that fully recovered ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4832383 Fri, 13 May 2011 05:42:40 +0100 4832383 http://www.medworm.com/index.php?rid=4832384&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fv68u9662853g7623%2F Abstract  The quality of temporal coding of sound waveforms in the monaural afferents that converge on binaural neurons in the brainstem limits the sensitivity to temporal differences at the two ears. The anteroventral cochlear nucleus (AVCN) houses the cells that project to the binaural nuclei, which are known to have enhanced temporal coding of low-frequency sounds relative to auditory nerve (AN) fibers. We applied a coincidence analysis within the framework of detection theory to investigate the extent to which AVCN processing affects interaural time delay (ITD) sensitivity. Using monaural spike trains to a 1-s broadband or narrowband noise token, we emulated the binaural task of ITD discrimination and calculated just noticeable differences (jnds). The ITD jnds derived f... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4832384 Thu, 12 May 2011 17:23:20 +0100 4832384 http://www.medworm.com/index.php?rid=4726226&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fl4253j3174hk6076%2F Abstract  Multiple-hour training on a pitch discrimination task dramatically decreases the threshold for detecting a pitch difference between two harmonic complexes. Here, we investigated the specificity of this perceptual learning with respect to the pitch and the resolvability of the trained harmonic complex, as well as its cortical electrophysiological correlates. We trained 24 participants for 12 h on a pitch discrimination task using one of four different harmonic complexes. The complexes differed in pitch and/or spectral resolvability of their components by the cochlea, but were filtered into the same spectral region. Cortical-evoked potentials and a behavioral measure of pitch discrimination were assessed before and after training for all the four complexes. The... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4726226 Tue, 12 Apr 2011 06:52:15 +0100 4726226 http://www.medworm.com/index.php?rid=4698959&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fy8u3682834070628%2F In this study, we used a knock-in reporter mouse to examine the spatiotemporal expression of Lgr5 in the cochlear duct during embryonic and postnatal periods. In the embryonic day 15.5 (E15.5) cochlear duct, Lgr5-EGFP is expressed in the floor epithelium and overlapped with the prosensory markers Sox2, Jagged1, and p27(Kip1). Nascent hair cells and supporting cells in the apical turn of the E18.5 cochlear duct express Lgr5-EGFP, which becomes downregulated in hair cells and subsets of supporting cells in more mature stages. In situ hybridization experiments validated the reporter expression, which gradually decreases until the second postnatal week. Only the third row of Deiters’ cells expresses Lgr5-EGFP in the mature organ of Corti. Normal cochlear development was observed i... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4698959 Thu, 07 Apr 2011 06:00:13 +0100 4698959 http://www.medworm.com/index.php?rid=4698960&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F7317843u3400l722%2F Abstract  Transforming growth factor-β-activated kinase-1 (TAK1) is a mitogen activated protein kinase kinase kinase that is involved in diverse biological roles across species. Functioning downstream of TGF-β and BMP signaling, TAK1 mediates the activation of the c-Jun N-terminal kinase signaling pathway, serves as the target of pro-inflammatory cytokines, such as TNF-α, mediates NF-κβ activation, and plays a role in Wnt/Fz signaling in mesenchymal stem cells. Expression of TAK1 in the cochlea has not been defined. Data mining of previously published murine cochlear gene expression databases indicated that TAK1, along with TAK1 interacting proteins 1 (TAB1), and 2 (TAB2), is expressed in the developing and adult cochlea. The expression of TAK1 in the developing cochle... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4698960 Thu, 07 Apr 2011 06:00:12 +0100 4698960 http://www.medworm.com/index.php?rid=4595906&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fk57127674454m473%2F Abstract  Presbycusis (age-related hearing loss) can result from various cochlear pathologies. We have studied the time course of degeneration in a mouse that shows accelerated presbycusis, the CD/1 mouse, as a possible model to investigate stem-cell strategies to prevent or ameliorate presbycusic changes. CD/1 mice from 0 to 72 weeks old were examined by light and electron microscopy. Early pathological changes were detected in basal turn spiral ligament fibrocytes and spiral ganglion, but the latter was variable as both satellite cells and neurons were normal in some cochleae. Light microscopic counts in the spiral ligament of 20-week-old mice revealed that of the five main types (types I–V), only type V fibrocytes showed no reduction in numbers compared with 3-wee... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4595906 Sat, 12 Mar 2011 06:59:16 +0100 4595906 http://www.medworm.com/index.php?rid=4581918&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fb84xv5136784143m%2F Abstract  There are known differences in the properties of hair cells along the tonotopic axis of the avian auditory epithelium, the basilar papilla (BP). To determine the genetic basis of these differences, we compared gene expression between the high- (HF), middle-, and low-frequency (LF) thirds of 0-day-old chick auditory epithelia. RNA amplified from each sample was hybridized to whole-genome chicken arrays and GeneSpring software was used to identify differentially expressed genes. Two thousand six hundred sixty-three genes were found to be differentially expressed between the HF and LF segments, using a fold-change cutoff of 2 and a p value of 0.05. Many ion channel genes were differentially expressed between the HF and LF regions of the BP, an expression pattern that... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4581918 Fri, 11 Mar 2011 18:06:47 +0100 4581918 http://www.medworm.com/index.php?rid=4581917&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fk761127gg77mu422%2F Abstract   Scleraxis (Scx) is a basic helix-loop-helix transcription factor expressed in tendon and ligament progenitor cells and the differentiated cells within these connective tissues in the axial and appendicular skeleton. Unexpectedly, we found expression of the Scx transgenic reporter mouse, Scx-GFP, in interdental cells, sensory hair cells, and cochlear supporting cells at embryonic day 18.5 (E18.5). We evaluated Scx-null mice to gain insight into the function of Scx in the inner ear. Paradoxical hearing loss was detected in Scx-nulls, with ~50% of the mutants presenting elevated auditory thresholds. However, Scx-null mice have no obvious, gross alterations in cochlear morphology or cellular patterning. Moreover, we show that the elevated auditory thresholds correl... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4581917 Fri, 11 Mar 2011 18:06:47 +0100 4581917 http://www.medworm.com/index.php?rid=4550391&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F2137x35m2278m5n6%2F Abstract  The mammalian cochlea has two types of sensory cells; inner hair cells, which receive auditory-nerve afferent innervation, and outer hair cells, innervated by efferent axons of the medial olivocochlear (MOC) system. The role of the MOC system in hearing is still controversial. Recently, by recording cochlear potentials in behaving chinchillas, we suggested that one of the possible functions of the efferent system is to reduce cochlear sensitivity during attention to other sensory modalities (Delano et al. in J Neurosci 27:4146–4153, 2007). However, in spite of these compelling results, the physiological effects of electrical MOC activation on cochlear potentials have not been described in detail in chinchillas. The main objective of the present work was to descri... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4550391 Wed, 02 Mar 2011 07:50:36 +0100 4550391 http://www.medworm.com/index.php?rid=4550392&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fw478r4782n72014l%2F Abstract  Of the two pathways through which we hear, air conduction (AC) and bone conduction (BC), the fundamental mechanisms of the BC pathway remain poorly understood, despite their clinical significance. A finite element model of a human middle ear and cochlea was developed to gain insight into the mechanisms of BC hearing. The characteristics of various cochlear response quantities, including the basilar membrane (BM) vibration, oval-window (OW) and round-window (RW) volume velocities, and cochlear fluid pressures were examined for BC as well as AC excitations. These responses were tuned and validated against available experimental data from the literature. BC excitations were simulated in the form of rigid body vibrations of the surrounding bony structures in the x, y,... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4550392 Tue, 01 Mar 2011 07:07:10 +0100 4550392 http://www.medworm.com/index.php?rid=4541655&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fw241371t1xuj6t5v%2F This study sought to examine whether part of the large interindividual variability of speech-recognition performance in individuals with severe-to-profound high-frequency hearing loss could be accounted for by differences in hearing-loss onset type (early, progressive, or sudden), age at hearing-loss onset, or hearing-loss duration. Other potential factors including age, hearing thresholds, speech-presentation levels, and speech audibility were controlled. Percent-correct (PC) scores for syllables in dissyllabic words, which were either unprocessed or lowpass filtered at cutoff frequencies ranging from 250 to 2,000 Hz, were measured in 20 subjects (40 ears) with severe-to-profound hearing losses above 1 kHz. For comparison purposes, 20 normal-hearing subjects (20 ears) were... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4541655 Fri, 25 Feb 2011 07:19:58 +0100 4541655 http://www.medworm.com/index.php?rid=4541656&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Frt5p23636uj25837%2F Abstract  The early onset of peripheral deafness profoundly alters the functional maturation of the central auditory system. A prolonged exposure to an artificial acoustic environment has a similar disruptive influence. These observations establish the importance of normal patterns of sound-driven activity during the initial stages of auditory development. The present study was designed to address the role of cochlear gain control during these activity-dependent developmental processes. It was hypothesized that the regulation of auditory nerve activity by the medial olivocochlear system (MOCS) would preserve normal development when the immature auditory system was challenged by continuous background noise. To test this hypothesis, knock-out mice lacking MOCS feedback were r... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4541656 Wed, 23 Feb 2011 23:30:41 +0100 4541656 http://www.medworm.com/index.php?rid=4415718&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F4w6l8548276m61t5%2F Abstract  Previous studies have found a significant correlation between spectral-ripple discrimination and speech and music perception in cochlear implant (CI) users. This relationship could be of use to clinicians and scientists who are interested in using spectral-ripple stimuli in the assessment and habilitation of CI users. However, previous psychoacoustic tasks used to assess spectral discrimination are not suitable for all populations, and it would be beneficial to develop methods that could be used to test all age ranges, including pediatric implant users. Additionally, it is important to understand how ripple stimuli are processed in the central auditory system and how their neural representation contributes to behavioral performance. For this reason, we developed a... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4415718 Thu, 27 Jan 2011 00:55:23 +0100 4415718 http://www.medworm.com/index.php?rid=4415719&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F1q3617j462612284%2F Abstract  Masked detection threshold for a short tone in noise improves as the tone’s onset is delayed from the masker’s onset. This improvement, known as “overshoot,” is maximal at mid-masker levels and is reduced by temporary and permanent cochlear hearing loss. Computational modeling was used in the present study to evaluate proposed physiological mechanisms of overshoot, including classic firing rate adaptation and medial olivocochlear (MOC) feedback, for both normal hearing and cochlear hearing loss conditions. These theories were tested using an established model of the auditory periphery and signal detection theory techniques. The influence of several analysis variables on predicted tone-pip detection in broadband noise was evaluated, including: auditory nerv... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4415719 Wed, 26 Jan 2011 19:46:24 +0100 4415719 http://www.medworm.com/index.php?rid=4327609&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm1rg390j2873x774%2F In this study, we analyze the processing of low-frequency sounds in the cochlear apex through responses of auditory nerve fibers (ANFs) that innervate the apex. Single tones and irregularly spaced tone complexes were used to evoke ANF responses in Mongolian gerbil. The spike arrival times were analyzed in terms of phase locking, peripheral frequency selectivity, group delays, and the nonlinear effects of sound pressure level (SPL). Phase locking to single tones was similar to that in cat. Vector strength was maximal for stimulus frequencies around 500 Hz, decreased above 1 kHz, and became insignificant above 4 to 5 kHz. We used the responses to tone complexes to determine amplitude and phase curves of ANFs having a characteristic frequency (CF) below 5 kHz. With i... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4327609 Fri, 07 Jan 2011 06:49:38 +0100 4327609 http://www.medworm.com/index.php?rid=4289195&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm36481284p724u76%2F Abstract  Wojtczak and Viemeister (J Acoust Soc Am 118:3198–3210, 2005) demonstrated forward masking in the amplitude-modulation (AM) domain. The present study examined whether this effect has correlates in physiological responses to AM at the level of the auditory midbrain. The human psychophysical experiment used 40-Hz, 100% AM (masker AM) that was imposed on a 5.5-kHz carrier during the first 150 ms of its duration. The masker AM was followed by a 50-ms burst of AM of the same rate (signal AM) imposed on the same (uninterrupted) carrier, either immediately after the masker or with a delay. In the physiological experiment, single-unit extracellular recordings in the awake rabbit inferior colliculus (IC) were obtained for stimuli designed to be similar to the uninter... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4289195 Wed, 22 Dec 2010 20:16:00 +0100 4289195 http://www.medworm.com/index.php?rid=4246624&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fq230627p7068033q%2F This study focuses upon a comparison of emission properties in two phylogenetically similar pairs of gecko: Gekko gecko and Hemidactylus turcicus and Eublepharis macularius and Coleonyx variegatus. Each pair consists of two closely related species within the same subfamily, with quantitatively known morphological properties at the level of the auditory sensory organ (basilar papilla) in the inner ear. Essentially, the comparison boils down to an issue of size: how does overall body size, as well as the inner-ear dimensions (e.g., papilla length and number of hair cells), affect peripheral auditory function as inferred from OAEs? Estimates of frequency selectivity derived from stimulus-frequency emissions (emissions evoked by a single low-level tone) indicate that tuning is broader in ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4246624 Tue, 07 Dec 2010 06:54:46 +0100 4246624 http://www.medworm.com/index.php?rid=4231158&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fhl071x32872623hj%2F Abstract  Listeners can selectively attend to a desired target by directing attention to known target source features, such as location or pitch. Reverberation, however, reduces the reliability of the cues that allow a target source to be segregated and selected from a sound mixture. Given this, it is likely that reverberant energy interferes with selective auditory attention. Anecdotal reports suggest that the ability to focus spatial auditory attention degrades even with early aging, yet there is little evidence that middle-aged listeners have behavioral deficits on tasks requiring selective auditory attention. The current study was designed to look for individual differences in selective attention ability and to see if any such differences correlate with age. Normal-hear... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4231158 Fri, 03 Dec 2010 06:58:05 +0100 4231158 http://www.medworm.com/index.php?rid=4226721&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F94l8740256569462%2F Abstract  A series of experiments investigated the effects of asymmetric current waveforms on the perception of place and temporal pitch cues. The asymmetric waveforms were trains of pseudomonophasic (PS) pulses consisting of a short, high-amplitude phase followed by a longer (and lower amplitude) opposite-polarity phase. When such pulses were presented in a narrow bipolar (“BP+1”) mode and with the first phase anodic relative to the most apical electrode (so-called PSA pulses), pitch was lower than when the first phase was anodic re the more basal electrode. For a pulse rate of 12 pulses per second (pps), pitch was also lower than with standard symmetric biphasic pulses in either monopolar or bipolar mode. This suggests that PSA pulses can extend the range of place-pit... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4226721 Tue, 30 Nov 2010 07:01:41 +0100 4226721 http://www.medworm.com/index.php?rid=4204072&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fc12756341m7486k7%2F Abstract  The tuning of a linear filter may be inferred from the filter’s isoresponse (e.g., tuning curves) or isoinput (e.g., isolevel curves) characteristics. This paper provides a theoretical demonstration that for nonlinear filters with compressive response characteristics like those of the basilar membrane, isoresponse measures can suggest strikingly sharper tuning than isoinput measures. The practical significance of this phenomenon is demonstrated by inferring the 3-dB-down bandwidths (BW3dB) of human auditory filters at 500 and 4,000 Hz from behavioral isoresponse and isoinput measures obtained with sinusoidal and notched noise forward maskers. Inferred cochlear responses were compressive for the two types of maskers. Consistent with expectations, low-level BW... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4204072 Tue, 23 Nov 2010 06:58:05 +0100 4204072 http://www.medworm.com/index.php?rid=4187443&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F214m86x26p3305uh%2F Abstract  A fundamental attribute of human hearing is the ability to extract a residue pitch from harmonic complex sounds such as those produced by musical instruments and the human voice. However, the neural mechanisms that underlie this processing are unclear, as are the locations of these mechanisms in the auditory pathway. The ability to extract a residue pitch corresponding to the fundamental frequency from individual harmonics, even when the fundamental component is absent, has been demonstrated separately for conventional pitches and for Huggins pitch (HP), a stimulus without monaural pitch information. HP is created by presenting the same wideband noise to both ears, except for a narrowband frequency region where the noise is decorrelated across the two ears. The pr... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4187443 Thu, 18 Nov 2010 07:56:34 +0100 4187443 http://www.medworm.com/index.php?rid=4180219&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F651j6p56x1726225%2F We report that forward-masker pulse trains can enhance and reduce ANF responsiveness to subsequent stimuli and the novel observation that sub-threshold (nonspike-evoking) electric trains can reduce responsiveness to subsequent pulse-train stimuli. The effect is observed in the responses of cat ANFs and shown by a computational biophysical ANF model that simulates rate adaptation through integration of external potassium cation (K) channels. Both low-threshold (i.e., Klt) and high-threshold (Kht) channels were simulated at each node of Ranvier. Model versions without Klt channels did not produce the sub-threshold effect. These results suggest that some such accumulation mechanism, along with Klt channels, may underlie sub-threshold masking observed in cat ANF responses. As multichann... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4180219 Tue, 16 Nov 2010 07:09:42 +0100 4180219 http://www.medworm.com/index.php?rid=4156261&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F16778lt71l483344%2F Abstract  In the present study, glial cell responses to spiral ganglion neuron (SGN) degeneration were evaluated using a murine model of auditory neuropathy. Ouabain, a well-known Na,K-ATPase inhibitor, has been shown to induce SGN degeneration while sparing hair cell function. In addition to selectively removing type I SGNs, ouabain leads to hyperplasia and hypertrophy of glia-like cells in the injured auditory nerves. As the transcription factor Sox2 is predominantly expressed in proliferating and undifferentiated neural precursors during neurogenesis, we sought to examine Sox2 expression patterns following SGN injury by ouabain. Real-time RT-PCR and Western blot analyses of cochlea indicated a significant increase in Sox2 expression by 3 days post-treatment with oua... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4156261 Tue, 09 Nov 2010 07:49:59 +0100 4156261 http://www.medworm.com/index.php?rid=4156260&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F90vhm885n0653278%2F Abstract  Spontaneous otoacoustic emissions can be detected as peaks in the Fourier spectrum of a microphone signal recorded from the ear canal. The height, center frequency, and spectral width of SOAE peaks changed when a static pressure was applied to the ear canal. Most commonly, with either increasing or decreasing static pressure, the frequency increased, the amplitude decreased, and the width increased. These changes are believed to result from changes in the middle ear properties. Specifically, reduced middle ear transmission is assumed to attenuate the amplitude of emissions. We reconsidered this explanation by investigating the relation between peak height and width. We showed that the spectral width of SOAE peaks is approximately proportional to 1/Ö   ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4156260 Tue, 09 Nov 2010 07:49:59 +0100 4156260 http://www.medworm.com/index.php?rid=4145419&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fx5357475454m5210%2F Abstract  Recent clinical studies have demonstrated that auditory cortex electrical stimulation (ACES) has yielded promising results in the suppression of patients’ tinnitus. However, the large variability in the efficacy of ACES-induced suppression across individuals has hindered its development into a reliable therapy. Due to ethical reasons, many issues cannot be comprehensively addressed in patients. In order to search for effective stimulation targets and identify optimal stimulation strategies, we have developed the first rat model to test for the suppression of behavioral evidence of tone-induced tinnitus through ACES. Our behavioral results demonstrated that electrical stimulation of all channels (frequency bands) in the auditory cortex significantly suppressed be... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4145419 Sat, 06 Nov 2010 20:20:46 +0100 4145419 http://www.medworm.com/index.php?rid=4141258&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F4221257m4x0w7t13%2F Abstract  The CBA/CaJ mouse strain is commonly used as a control as it has no known genetic mutations affecting the inner ear, maintains hearing sensitivity throughout life, and serves as a background for creating new genetic strains. The purpose of the present study was to characterize the effects of age and gender on gravity receptor function and compare functional changes between auditory and vestibular modalities. Vestibular-evoked potentials (VsEPs), auditory brainstem responses (ABRs), and distortion product otoacoustic emissions were measured in 131 mice. VsEP thresholds deteriorated an average of 0.39 dB re: 1.0 g/ms per month and at the oldest ages (18–23 months old) showed an average loss of 49% of VsEP dynamic range. No significant gender differe... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4141258 Fri, 05 Nov 2010 10:53:37 +0100 4141258 http://www.medworm.com/index.php?rid=4141259&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F3q84568536t2vk33%2F This report describes newly discovered extralabyrinthine findings within the middle ear in DFNA9 and discusses their implications. The histopathologic anatomy of extralabyrinthine structures was reviewed in 12 temporal bones from seven individuals with DFNA9 and compared with age-matched controls. All temporal bones with DFNA9 had abnormal deposits within the tympanic membrane, incudomalleal joint, and incudostapedial joint. Hematoxylin and eosin stain and Movat’s pentachrome stain both revealed different staining patterns of the extralabyrinthine deposits compared with the intralabyrinthine deposits suggesting that the composition of the deposits varies with location. The deposits within the tympanic membrane resembled cartilage morphologically and stained positively for aggrecan,... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4141259 Fri, 05 Nov 2010 10:53:35 +0100 4141259 http://www.medworm.com/index.php?rid=4120626&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fq06x457340510x2j%2F Abstract  Mosquitoes are more sensitive to sound than any other insect due to the remarkable properties of their antennae and Johnston’s organ at the base of each antenna. Male mosquitoes detect and locate female mosquitoes by hearing the female’s flight tone, but until recently we had no idea that females also respond to male flight tones. Our investigation of a novel mechanism of sex recognition in Toxorhynchites brevipalpis revealed that male and female mosquitoes actively respond to the flight tones of other flying mosquitoes by altering their own wing-beat frequencies. Male–female pairs converge on a shared harmonic of their respective fundamental flight tones, whereas same sex pairs diverge. Most frequency matching occurs at frequencies beyond the detection range... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4120626 Tue, 26 Oct 2010 06:49:54 +0100 4120626 http://www.medworm.com/index.php?rid=4090244&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fu222104912618765%2F Abstract  The cochlear microphonic (CM) can be a useful analytical tool, but many investigators may not be fully familiar with its unique properties to interpret it accurately in mouse models of hearing. The purpose of this report is to develop a model for generation of the CM in wild-type (WT) and prestin knockout mice. Data and modeling results indicate that in the majority of cases, the CM is a passive response, and in the absence of outer hair cell (OHC) damage, mice lacking amplification are expected to generate WT levels of CM for inputs less than ~30 kHz. Hence, this cochlear potential is not a useful metric to estimate changes in amplifier gain. This modeling analysis may explain much of the paradoxical data in the literature. For example, various manipulations,... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4090244 Tue, 19 Oct 2010 23:37:32 +0100 4090244 http://www.medworm.com/index.php?rid=4090245&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fa8830051562822w0%2F Abstract  Sounds are filtered in a spatial- and frequency-dependent manner by the head and pinna giving rise to the acoustical cues to sound source location. These spectral and temporal transformations are dependent on the physical dimensions of the head and pinna. Therefore, the magnitudes of binaural sound location cues—the interaural time (ITD) and level (ILD) differences—are hypothesized to systematically increase while the lower frequency limit of substantial ILD production is expected to decrease due to the increase in head and pinna size during development. The frequency ranges of the monaural spectral notch cues to source elevation are also expected to decrease. This hypothesis was tested here by measuring directional transfer functions (DTFs), the directional c... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4090245 Tue, 19 Oct 2010 23:37:30 +0100 4090245 http://www.medworm.com/index.php?rid=4069036&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F017671425g575759%2F Abstract  The nicotinic acetylcholine receptor (AChR) current of outer hair cells (OHCs) was investigated in isolated and voltage-clamped cells under conditions where co-activating Ca2+-activated K+ currents had been abolished using internal BAPTA, external calcium removal and/or depolarisation to positive voltages. The AChR current activated rapidly and thereafter declined in the continued presence of ACh. Reversal potential measurements indicated that it was a non-specific cation current with a substantial Ca2+ permeability. It had a characteristic bidirectional rectification with an especially prominent outward component in solutions containing 1 mM Ca2+. The I–V relation was fitted with a single-energy barrier model. The fit suggests a blocking site within the chan... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4069036 Wed, 13 Oct 2010 05:50:20 +0100 4069036 http://www.medworm.com/index.php?rid=4051904&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fd7638402u428p731%2F Abstract  The acute and permanent effects of noise exposure on the endocochlear potential (EP) and cochlear lateral wall were evaluated in BALB/cJ (BALB) inbred mice, and compared with CBA/J (CBA) and C57BL/6 (B6) mice. Two-hour exposure to broadband noise (4–45 kHz) at 110 dB SPL leads to a ~50 mV reduction in the EP in BALB and CBA, but not B6. EP reduction in BALB and CBA is reliably associated with characteristic acute cellular pathology in stria vascularis and spiral ligament. By 8 weeks after exposure, the EP in CBA mice has returned to normal. In BALBs, however, the EP remains depressed by an average ~10 mV, so that permanent EP reduction contributes to permanent threshold shifts in these mice. We recently showed that the CBA noise phenotype... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4051904 Tue, 05 Oct 2010 05:46:34 +0100 4051904 http://www.medworm.com/index.php?rid=4019590&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fn4332216547m3rr5%2F In this study, we investigated changes of the frequency-following response (FFR), a subcortical component of the auditory evoked potentials, after a period of pitch discrimination training. Twenty-seven adult listeners were trained for 10 h on a pitch discrimination task using one of three different complex tone stimuli. One had a static pitch contour, one had a rising pitch contour, and one had a falling pitch contour. Behavioral measures of pitch discrimination and FFRs for all the stimuli were measured before and after the training phase for these participants, as well as for an untrained control group (n = 12). Trained participants showed significant improvements in pitch discrimination compared to the control group for all three trained stimuli. These improvements were ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4019590 Tue, 28 Sep 2010 05:48:47 +0100 4019590 http://www.medworm.com/index.php?rid=4005743&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fj047w1w3rt165lpv%2F Abstract  The pitch of the missing fundamental (F0) is one of the principal psychological attributes of human pitch perception. Behavioral responses to harmonic tone complexes having missing F0s were measured in chinchillas using operant conditioning and stimulus generalization. Animals were trained to discriminate between tone complexes having a 500-Hz F0 and a 125-Hz F0. When animals were tested with tone complexes having the same F0s, but where the F0s were missing, responses were similar to those obtained when the F0s were present, suggesting that missing F0 sounds were perceptually equivalent to F0 present sounds. Behavioral responses to F0 present and missing F0 stimuli were similar in the presence of low-pass masking noise, suggesting that the perception was not due ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=4005743 Sat, 25 Sep 2010 05:56:15 +0100 4005743 http://www.medworm.com/index.php?rid=3978417&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fw5174347l55587t8%2F In this study, emission data from Mongolian gerbils are reported that were obtained with stimuli consisting of six to 10 tones. The stimuli were constructed by replacing one of the tones of a tone pair by a narrowband multitone complex. This produced rich spectra of the ear canal sound pressure in which many of the third-order DPOAEs originated from the interaction of triplets of stimulus components. A careful choice of the stimulus frequencies ensured that none of these DPOAE components coincided. Three groups of DPOAEs are reported, two of which are closely related to DPOAEs evoked by tone pairs. The third group has no two-tone equivalent and only arises when using a multitone stimulus. We analyzed the relation between multitone-evoked DPOAEs and DPOAEs evoked by tone pairs, and e... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3978417 Tue, 14 Sep 2010 05:58:39 +0100 3978417 http://www.medworm.com/index.php?rid=3978416&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F68518333x3l01v83%2F We examined horizontal directional hearing in patients with acquired severe unilateral conductive hearing loss (UCHL). All patients (n = 12) had been fitted with a bone conduction device (BCD) to restore bilateral hearing. The patients were tested in the unaided (monaural) and aided (binaural) hearing condition. Five listeners without hearing loss were tested as a control group while listening with a monaural plug and earmuff, or with both ears (binaural). We randomly varied stimulus presentation levels to assess whether listeners relied on the acoustic head-shadow effect (HSE) for horizontal (azimuth) localization. Moreover, to prevent sound localization on the basis of monaural spectral shape cues from head and pinna, subjects were exposed to narrow band (1/3 octave) noises. We... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3978416 Tue, 14 Sep 2010 05:58:39 +0100 3978416 http://www.medworm.com/index.php?rid=3948261&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F4u62054086834w26%2F This study extended that body of work by examining the effects of sound level and background noise on the quality of spectral coding in the auditory nerve. When fibers were classified by their spontaneous rates, the coding properties of the more numerous low-threshold, high-spontaneous rate fibers were found to degrade at high presentation levels and in low signal-to-noise ratios. Because cats are known to maintain accurate directional hearing under these challenging listening conditions, behavioral performance may be disproportionally based on the enhanced dynamic range of the less common high-threshold, low-spontaneous rate fibers. Content Type Journal ArticleDOI 10.1007/s10162-010-0232-5Authors Lina A. J. Reiss, Department of Biomedical Engineering, Johns Hopkins University,... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3948261 Wed, 08 Sep 2010 12:18:19 +0100 3948261 http://www.medworm.com/index.php?rid=3948262&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F0g88066330jm6636%2F Abstract  It has long been observed that loss of auditory receptor cells is associated with the progressive degeneration of spiral ganglion cells. Chronic electrical stimulation via cochlear implantation has been used in an attempt to slow the rate of degeneration in cats neonatally deafened by ototoxic agents but with mixed results. The present study examined this issue using white cats with a history of hereditary deafness as an alternative animal model. Nineteen cats provided new data for this study: four normal-hearing cats, seven congenitally deaf white cats, and eight congenitally deaf white cats with unilateral cochlear implants. Data from additional cats were collected from the literature. Electrical stimulation began at 3 to 4 or 6 to 7 months after birth, and... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3948262 Tue, 07 Sep 2010 06:29:46 +0100 3948262 http://www.medworm.com/index.php?rid=3948263&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fy04w5r638007663p%2F Abstract  The mammalian inner ear contains sense organs responsible for detecting sound, gravity and linear acceleration, and angular acceleration. Of these organs, the cochlea is involved in hearing, while the sacculus and utriculus serve to detect linear acceleration. Recent evidence from birds and mammals, including humans, has shown that the sacculus, a hearing organ in many lower vertebrates, has retained some of its ancestral acoustic sensitivity. Here we provide not only more evidence for the retained acoustic sensitivity of the sacculus, but we also found that acoustic stimulation of the sacculus has behavioral significance in mammals. We show that the amplitude of an elicited auditory startle response is greater when the startle stimuli are presented simultaneously... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3948263 Tue, 07 Sep 2010 06:29:45 +0100 3948263 http://www.medworm.com/index.php?rid=3930622&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F41q782tm8w112032%2F Abstract  Hair cells, the mechanosensitive receptor cells of the inner ear, are critical for our senses of hearing and balance. The small number of these receptor cells in the inner ear has impeded the identification and characterization of proteins important for hair cell function. The binding specificity of monoclonal antibodies provides a means for identifying hair cell-specific proteins and isolating them for further study. We have generated a monoclonal antibody, termed hair cell soma-1 (HCS-1), which specifically immunolabels hair cells in at least five vertebrate classes, including sharks and rays, bony fish, amphibians, birds, and mammals. We used HCS-1 to immunoprecipitate the cognate antigen and identified it as otoferlin, a member of the ferlin protein family. Mu... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3930622 Thu, 02 Sep 2010 06:36:35 +0100 3930622 http://www.medworm.com/index.php?rid=3882896&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fe3734t4u427285p4%2F This study was motivated by the need to determine in which region to implant the single shank array within a three-dimensional ICC structure and what stimulus parameters to use in patients. Our findings indicate that complex and unfavorable cortical activation properties are elicited by stimulation of caudal–dorsal ICC regions with the AMI array. Our results also confirm the existence of different functional regions along the isofrequency domain of the ICC (i.e., a caudal–dorsal and a rostral–ventral region), which has been traditionally unclassified. Based on our study as well as previous animal and human AMI findings, we may need to deliver more complex stimuli than currently used in the AMI patients to effectively activate the caudal ICC or ensure that the single shank AMI i... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3882896 Wed, 18 Aug 2010 06:46:25 +0100 3882896 http://www.medworm.com/index.php?rid=3866037&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F37x207784675r828%2F Abstract  Two inbred mouse strains, CBA/J and CBA/CaJ, have been used nearly interchangeably as ‘good hearing’ standards for research in hearing and deafness. We recently reported, however, that these two strains diverge after 1 year of age, such that CBA/CaJ mice show more rapid elevation of compound action potential (CAP) thresholds at high frequencies (Ohlemiller, Brain Res. 1277: 70–83, 2009). One contributor is progressive decline in endocochlear potential (EP) that appears only in CBA/CaJ. Here, we explore the cellular bases of threshold and EP disparities in old CBA/J and CBA/CaJ mice. Among the major findings, both strains exhibit a characteristic age (∼18 months in CBA/J and 24 months in CBA/CaJ) when females overtake males in sensitivity decl... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3866037 Fri, 13 Aug 2010 07:05:48 +0100 3866037 http://www.medworm.com/index.php?rid=3792030&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F24xj928765041378%2F Abstract  The perceptual organization of sound sequences into auditory streams involves the integration of sounds into one stream and the segregation of sounds into separate streams. “Objective” psychophysical measures of auditory streaming can be obtained using behavioral tasks where performance is facilitated by segregation and hampered by integration, or vice versa. Traditionally, these two types of tasks have been tested in separate studies involving different listeners, procedures, and stimuli. Here, we tested subjects in two complementary temporal-gap discrimination tasks involving similar stimuli and procedures. One task was designed so that performance in it would be facilitated by perceptual integration; the other, so that performance would be facilitated by pe... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3792030 Sat, 24 Jul 2010 13:29:17 +0100 3792030 http://www.medworm.com/index.php?rid=3773949&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fd8m6882077u36g17%2F Abstract  Response rates of auditory nerve fibers (ANFs) to electric pulse trains change over time, reflecting substantial spike-rate adaptation that depends on stimulus parameters. We hypothesize that adaptation affects the representation of amplitude-modulated pulse trains used by cochlear prostheses to transmit speech information to the auditory system. We recorded cat ANF responses to sinusoidally amplitude-modulated (SAM) trains with 5,000 pulse/s carriers. Stimuli delivered by a monopolar intracochlear electrode had fixed modulation frequency (100 Hz) and depth (10%). ANF responses were assessed by spike-rate measures, while representation of modulation was evaluated by vector strength (VS) and the fundamental component of the fast Fourier transform (F0 amplitude... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3773949 Fri, 16 Jul 2010 16:52:39 +0100 3773949 http://www.medworm.com/index.php?rid=3773950&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fh25827u4vq13q687%2F Abstract  Mutations in the GJB2 gene encoding for the connexin 26 (Cx26) protein are the most common source of nonsyndromic forms of deafness. Cx26 is a building block of gap junctions (GJs) which establish electrical connectivity in distinct cochlear compartments by allowing intercellular ionic (and metabolic) exchange. Animal models of the Cx26 deficiency in the organ of Corti seem to suggest that the hearing loss and the degeneration of outer hair cells (OHCs) and inner hair cells is due to failed K+ and metabolite homeostasis. However, OHCs can develop normally in some mutants, suggesting that the hair cells death is not the universal mechanism. In search for alternatives, we have developed an in silico large scale three-dimensional model of electrical current flow in th... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3773950 Fri, 16 Jul 2010 07:21:11 +0100 3773950 http://www.medworm.com/index.php?rid=3708234&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F1h2302068684183g%2F In this study, we examined the excitatory portion of the CN-commissural pathway by combining anterograde tract tracing with immunohistochemistry of vesicular glutamate transporters (VGLUTs) and retrograde tract tracing with immunohistochemistry of glycine and GABA. VGLUTs accumulate glutamate in synaptic vesicles and are prime markers for glutamatergic neurons. The terminal endings of CN-commissural projections were typically en passant or small terminal boutons, but large, irregular swellings were also observed, confined to the granule cell domain (GCD). Both small and large terminal endings in the GCD colabeled with VGLUT2, but not VGLUT1. In addition, some CN-commissural cells themselves received VGLUT2-positive puncta on their somata. After large injections into the CN, 37% of th... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3708234 Fri, 25 Jun 2010 17:07:38 +0100 3708234 http://www.medworm.com/index.php?rid=3673739&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F256l73362l5v76h5%2F Abstract  Recent perceptual studies suggest that listeners with sensorineural hearing loss (SNHL) have a reduced ability to use temporal fine-structure cues, whereas the effects of SNHL on temporal envelope cues are generally thought to be minimal. Several perceptual studies suggest that envelope coding may actually be enhanced following SNHL and that this effect may actually degrade listening in modulated maskers (e.g., competing talkers). The present study examined physiological effects of SNHL on envelope coding in auditory nerve (AN) fibers in relation to fine-structure coding. Responses were compared between anesthetized chinchillas with normal hearing and those with a mild–moderate noise-induced hearing loss. Temporal envelope coding of narrowband-modulated stimuli ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3673739 Thu, 17 Jun 2010 09:18:22 +0100 3673739 http://www.medworm.com/index.php?rid=3650029&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F874u1791r264t129%2F Abstract  Four cochlear implant users, having normal hearing in the unimplanted ear, compared the pitches of electrical and acoustic stimuli presented to the two ears. Comparisons were between 1,031-pps pulse trains and pure tones or between 12 and 25-pps electric pulse trains and bandpass-filtered acoustic pulse trains of the same rate. Three methods—pitch adjustment, constant stimuli, and interleaved adaptive procedures—were used. For all methods, we showed that the results can be strongly influenced by non-sensory biases arising from the range of acoustic stimuli presented, and proposed a series of checks that should be made to alert the experimenter to those biases. We then showed that the results of comparisons that survived these checks do not deviate consistently... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3650029 Mon, 07 Jun 2010 19:30:22 +0100 3650029 http://www.medworm.com/index.php?rid=3650030&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fp5035464x30n6236%2F Abstract  There are numerous studies measuring the transfer functions representing signal transformation between a source and each ear canal, i.e., the head-related transfer functions (HRTFs), for various species. However, only a handful of these address the effects of sound source distance on HRTFs. This is the first study of HRTFs in the rabbit where the emphasis is on the effects of sound source distance and azimuth on HRTFs. With the rabbit placed in an anechoic chamber, we made acoustic measurements with miniature microphones placed deep in each ear canal to a sound source at different positions (10–160 cm distance, ±150° azimuth). The sound was a logarithmically swept broadband chirp. For comparisons, we also obtained the HRTFs from a racquetball and a comput... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3650030 Mon, 07 Jun 2010 19:30:21 +0100 3650030 http://www.medworm.com/index.php?rid=3611196&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ft12225h56vh840m7%2F Abstract  The vasculature and neurons of the inner ear receive adrenergic innervation from the cervical sympathetic chain, and adrenergic receptors may be expressed by cells of the organ of Corti and stria vascularis, despite a lack of direct sympathetic innervation. To assess the functional role of adrenergic signaling in the auditory periphery, we studied mice with targeted deletion of the gene for dopamine β-hydroxylase (DBH), which catalyzes the conversion of dopamine to noradrenaline; thus, these mutant mice have no measurable adrenaline or noradrenaline. Dbh −/− mice were more susceptible to spontaneous middle-ear infection than their control littermates, consistent with a role for sympathetics in systemic and/or local immune response. At 6–8 weeks of age,... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3611196 Wed, 26 May 2010 14:48:24 +0100 3611196 http://www.medworm.com/index.php?rid=3539929&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F86462m8478667628%2F Abstract  We analyze published auditory-nerve and otoacoustic measurements in chinchilla to test a network of hypothesized relationships between cochlear tuning, cochlear traveling-wave delay, and stimulus-frequency otoacoustic emissions (SFOAEs). We find that the physiological data generally corroborate the network of relationships, including predictions from filter theory and the coherent-reflection model of OAE generation, at locations throughout the cochlea. The results support the use of otoacoustic emissions as noninvasive probes of cochlear tuning. Developing this application, we find that tuning ratios—defined as the ratio of tuning sharpness to SFOAE phase-gradient delay in periods—have a nearly species-invariant form in cat, guinea pig, and chinchilla. Analysi... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3539929 Tue, 04 May 2010 07:59:28 +0100 3539929 http://www.medworm.com/index.php?rid=3523497&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fa80625370t286376%2F Content Type Journal ArticleCategory ErratumDOI 10.1007/s10162-010-0219-2Authors Stefan L. R. Gea, University of Antwerp Biomedical Physics Groenenborgerlaan 171 2020 Antwerp BelgiumWillem F. Decraemer, University of Antwerp Biomedical Physics Groenenborgerlaan 171 2020 Antwerp BelgiumW. Robert J. Funnell, McGill University Department of BioMedical Engineering Montréal CanadaJoris J. J. Dirckx, University of Antwerp Biomedical Physics Groenenborgerlaan 171 2020 Antwerp BelgiumHannes Maier, HNO Universitätsklinikum Hamburg-Eppendorf Martinistr. 52 20246 Hamburg Germany Journal JARO - Journal of the Association for Research in OtolaryngologyOnline ISSN 1438-7573Print ISSN 1525-3961 (Source: JARO - Journal of the Association for Research in Otolaryngology) JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3523497 Thu, 29 Apr 2010 19:45:34 +0100 3523497 http://www.medworm.com/index.php?rid=3495671&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F4x8521mx82155ur2%2F Abstract  Vestibular hair cells transduce mechanical displacements of their hair bundles into an electrical receptor potential which modulates transmitter release and subsequent action potential firing in afferent neurons. To probe ionic mechanisms underlying sensory coding in vestibular calyces, we used the whole-cell patch-clamp technique to record action potentials and K+ currents from afferent calyx terminals isolated from the semicircular canals of Mongolian gerbils. Calyx terminals showed minimal current at the mean zero-current potential (−60 mV), but two types of outward K+ currents were identified at potentials above −50 mV. The first current was a rapidly activating and inactivating K+ current that was blocked by 4-aminopyridine (4-AP, 2.5 mM) and ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3495671 Wed, 21 Apr 2010 08:59:54 +0100 3495671 http://www.medworm.com/index.php?rid=3481607&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fb2815071r4k21879%2F Abstract  Auditory transduction, amplification, and hair cell survival depend on the regulation of extracellular [K+] in the cochlea. K+ is removed from the vicinity of sensory hair cells by epithelial cells, and may be distributed through the epithelial cell syncytium, reminiscent of “spatial buffering” in glia. Hypothetically, K+ is then transferred from the epithelial syncytium into the connective tissue syncytium within the cochlear lateral wall, enabling recirculation of K+ back into endolymph. This may involve secretion of K+ from epithelial root cells, and its re-uptake via transporters into spiral ligament fibrocytes. The molecular basis of this secretion is not known. Using a combination of approaches we demonstrated that the resting conductance in guinea pig root... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3481607 Thu, 15 Apr 2010 06:47:54 +0100 3481607 http://www.medworm.com/index.php?rid=3477232&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F261745177g228048%2F In this study, we explored the possibility that specific CD proteins might be useful for defining inner ear cell populations. mRNA expression profiling of microdissected auditory and vestibular sensory epithelia revealed 107 CD genes as expressed in the early postnatal mouse inner ear. The expression of 68 CD genes was validated with real-time RT-PCR using RNA extracted from microdissected sensory epithelia of cochleae, utricles, saccules, and cristae of newborn mice. Specifically, CD44 was identified as preferentially expressed in the auditory sensory epithelium. Immunohistochemistry revealed that within the early postnatal organ of Corti, the expression of CD44 is restricted to outer pillar cells. In order to confirm and expand this finding, we characterized the expression of CD44 ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3477232 Tue, 13 Apr 2010 06:47:40 +0100 3477232 http://www.medworm.com/index.php?rid=3450988&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fv0733nmp83m670nw%2F Abstract  Gerbils aged in quiet show a decline of the endocochlear potential (EP) and elevated auditory nerve compound action potential (CAP) thresholds. However, establishing a direct relationship between an age-related reduction in the EP and changes in the activities of primary auditory neurons is difficult owing to the complexity of age-related histological changes in the cochlea. To address this issue, we developed a young gerbil model of “metabolic” presbyacusis that uses an osmotic pump to deliver furosemide into the round window niche for 7 days, resulting in a chronically reduced EP. In this model, the only major histopathologic changes were restricted to the hook region of the cochlea and consisted of loss of strial intermediate cells and massive edema in... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3450988 Tue, 06 Apr 2010 18:08:38 +0100 3450988 http://www.medworm.com/index.php?rid=3450987&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F527tr5gx63462003%2F Abstract  The use of binaural pitch stimuli to test for the presence of binaural auditory impairment in reading-disabled subjects has so far led to contradictory outcomes. While some studies found that a majority of dyslexic subjects was unable to perceive binaural pitch, others obtained a clear response of dyslexic listeners to Huggins’ pitch (HP). The present study clarified whether impaired binaural pitch perception is found in dyslexia. Results from a pitch contour identification test, performed in 31 dyslexic listeners and 31 matched controls, clearly showed that dyslexics perceived HP as well as the controls. Both groups also showed comparable results with a similar-sounding, but monaurally detectable, pitch-evoking stimulus. However, nine of the dyslexic subjects w... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3450987 Tue, 06 Apr 2010 18:08:38 +0100 3450987 http://www.medworm.com/index.php?rid=3450989&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F7507h465000661j6%2F Abstract  Psychophysical forward masking is an increase in threshold of detection of a sound (probe) when it is preceded by another sound (masker). This is reminiscent of the reduction in neuronal responses to a sound following prior stimulation. Studies in the auditory nerve and cochlear nucleus using signal detection theory techniques to derive neuronal thresholds showed that in centrally projecting neurons, increases in masked thresholds were significantly smaller than the changes measured psychophysically. Larger threshold shifts have been reported in the inferior colliculus of awake marmoset. The present study investigated the magnitude of forward masking in primary auditory cortical neurons of anaesthetised guinea-pigs. Responses of cortical neurons to unmasked and fo... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3450989 Tue, 06 Apr 2010 05:35:29 +0100 3450989 http://www.medworm.com/index.php?rid=3434136&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F40n4v8m713062q8x%2F Abstract  Many past studies of sound localization explored the precedence effect (PE), in which a pair of brief, temporally close sounds from different directions is perceived as coming from a location near that of the first-arriving sound. Here, a computational model of low-frequency inferior colliculus (IC) neurons accounts for both physiological and psychophysical responses to PE click stimuli. In the model, IC neurons have physiologically plausible inputs, receiving excitation from the ipsilateral medial superior olive (MSO) and long-lasting inhibition from both ipsilateral and contralateral MSOs, relayed through the dorsal nucleus of the lateral lemniscus. In this model, physiological suppression of the lagging response depends on the inter-stimulus delay (ISD) between... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3434136 Thu, 01 Apr 2010 07:48:56 +0100 3434136 http://www.medworm.com/index.php?rid=3304185&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ft153241521143027%2F Abstract  The avian inner ear possesses a remarkable ability to regenerate sensory hair cells after ototoxic injury. Regenerated hair cells possess phenotypes and innervation that are similar to those found in the undamaged ear, but little is known about the signaling pathways that guide hair cell differentiation during the regenerative process. The aim of the present study was to examine the factors that specify the orientation of hair cell stereocilia bundles during regeneration. Using organ cultures of the chick utricle, we show that hair cells are properly oriented after having regenerated entirely in vitro and that orientation is not affected by surgical removal of the striolar reversal zone. These results suggest that the orientation of regenerating stereocilia is not ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3304185 Tue, 23 Feb 2010 07:44:12 +0100 3304185 http://www.medworm.com/index.php?rid=3304184&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F3x602516nkt6020q%2F Abstract  The three-dimensional vestibulo-ocular reflex (3D VOR) ideally generates compensatory ocular rotations not only with a magnitude equal and opposite to the head rotation but also about an axis that is collinear with the head rotation axis. Vestibulo-ocular responses only partially fulfill this ideal behavior. Because animal studies have shown that vestibular stimulation about particular axes may lead to suboptimal compensatory responses, we investigated in healthy subjects the peaks and troughs in 3D VOR stabilization in terms of gain and alignment of the 3D vestibulo-ocular response. Six healthy upright sitting subjects underwent whole body small amplitude sinusoidal and constant acceleration transients delivered by a six-degree-of-freedom motion platform. Subject... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3304184 Tue, 23 Feb 2010 07:44:12 +0100 3304184 http://www.medworm.com/index.php?rid=3304186&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F91x3l08185134157%2F We report that the electrically evoked 3D angular vestibulo-ocular reflex exhibits vector superposition and linearity to a sufficient degree that a multichannel vestibular prosthesis incorporating a precompensatory 3D coordinate transformation to correct misalignment can accurately emulate semicircular canals for head rotations throughout the range of 3D axes normally transduced by a healthy labyrinth. Content Type Journal ArticleDOI 10.1007/s10162-010-0208-5Authors Gene Y. Fridman, Johns Hopkins School of Medicine Vestibular NeuroEngineering Laboratory, Department of Otolaryngology - Head & Neck Surgery Ross Bldg Rm 830, 720 Rutland Ave. Baltimore 11 MD 21205 USANatan S. Davidovics, Johns Hopkins School of Medicine Vestibular NeuroEngineering Laboratory, Department of Otolaryngo... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3304186 Tue, 23 Feb 2010 07:44:08 +0100 3304186 http://www.medworm.com/index.php?rid=3285412&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Frk003p1283076883%2F In this study, we characterized an organ culture model to study auditory hair cell regeneration, and we used these cultures to test if direct transdifferentiation alone can lead to significant hair cell regeneration. Control cultures (organs from posthatch chickens maintained without streptomycin) showed complete hair cell loss in the proximal (high-frequency) region by 5 days. In contrast, a 2-day treatment with streptomycin induced loss of hair cells from all regions by 3 days. Hair cell regeneration proceeded in culture, with the time course of supporting cell division and hair cell differentiation generally resembling in vivo patterns. The degree of supporting cell division depended upon the presence of streptomycin, the epithelial region, the type of culture media, an... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3285412 Wed, 17 Feb 2010 18:30:28 +0100 3285412 http://www.medworm.com/index.php?rid=3285411&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fj626648q84685845%2F In this study, velocity in a specific direction was measured at multiple points on the footplates of human temporal bones using a Scanning Laser Doppler Vibrometer (SLDV) system, and the elementary components of the stapes motions, which were the piston-like motion and the rocking motions about the short and long axes of the footplate, were calculated from the measurements. The angular position of a laser beam with respect to the stapes and coordinates of the measurement points on the footplate plane were calculated by correlation between the SLDV measurement frame and the footplate-fixed frame, which was obtained from micro-CT images. The ratios of the rocking motions relative to the piston-like motion increased with frequency and reached a maximum around 7 kHz. A novel me... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3285411 Wed, 17 Feb 2010 18:30:28 +0100 3285411 http://www.medworm.com/index.php?rid=3224034&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fy72q3736317184w0%2F Abstract  Sensorineural hearing deficiencies result from the loss of auditory hair cells. This hearing loss is permanent in humans and mammals because hair cells are not spontaneously replaced. In other animals such as birds, this is not the case. Damage to the avian cochlea evokes proliferation of supporting cells and the generation of functionally competent replacement hair cells. Signal transduction pathways are clinically useful as potential therapeutic targets, so there is significant interest in identifying the key signal transduction pathways that regulate the formation of replacement hair cells. In a previous study from our lab, we showed that forskolin (FSK) treatment induces auditory supporting cell proliferation and formation of replacement hair cells in the abse... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3224034 Wed, 27 Jan 2010 20:29:26 +0100 3224034 http://www.medworm.com/index.php?rid=3206180&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fv674436230g67272%2F Abstract  Animal studies indicate that a combination of kanamycin (KM) and noise produces a synergistic effect, whereby the threshold shift from the combination is greater than the sum of the shifts caused by either agent alone. Most such studies have focused on adult animals, and it has remained unclear whether younger, presumably more susceptible, animals show an even greater synergistic effect. The present study tested the hypothesis that young CBA/J mice receiving a low dose of KM (300 mg/kg, 2×/day, s.c.) from 20 to 30 days post-gestational age followed by brief noise exposure (110 dB SPL; 4–45 kHz, 30 s) would show greater noise-induced permanent threshold shifts (NIPTS) than mice receiving either treatment alone. Noise exposure produced 30�... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3206180 Fri, 22 Jan 2010 10:10:06 +0100 3206180 http://www.medworm.com/index.php?rid=3169031&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fqt3458w001380521%2F Abstract  The success of middle ear reconstructive surgery depends on stable coupling between the prosthesis and residual ossicles. To establish a stable fixed point on the stapes footplate for subsequent prosthesis reconstruction, a titanium footplate anchor was coated with osteoinductive substances to induce a controlled osseointegration on the footplate. Various studies have shown that collagen-based matrices with and without bone growth and differentiation factors can induce and enhance bone formation and consequently increase implant stability. The ears of 23 one-year-old Merino sheep (n = 46) were divided into five groups and implanted with a specially designed footplate anchor. The surface of each implant was modified by applying a collagenous matrix (collagen I o... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3169031 Tue, 12 Jan 2010 06:44:55 +0100 3169031 http://www.medworm.com/index.php?rid=3161038&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fx62237883r71w143%2F Abstract  The Notch signaling pathway is known to play important roles in inner ear development. Previous studies have shown that the Notch1 receptor and ligands in the Delta and Jagged families are important for cellular differentiation and patterning of the organ of Corti. Delta/notch-like epidermal growth factor (EGF)-related receptor (DNER) is a novel Notch ligand expressed in developing and adult CNS neurons known to promote maturation of glia through activation of Notch. Here we use in situ hybridization and an antibody against DNER to carry out expression studies of the mouse cochlea and vestibule. We find that DNER is expressed in spiral ganglion neuron cell bodies and peripheral processes during embryonic development of the cochlea and expression in these cells is ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3161038 Fri, 08 Jan 2010 09:09:38 +0100 3161038 http://www.medworm.com/index.php?rid=3121302&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fy6741kq35m327250%2F Abstract  In order to investigate whether performance in an auditory spatial discrimination task depends on the prevailing listening conditions, we tested the ability of human listeners to discriminate target sounds with and without presentation of a preceding sound. Target sounds were either lateralized by means of interaural time differences (ITDs) of +400, 0, or −400 μs or interaural level differences (ILDs) with the same subjective intracranial locations. The preceding sound was always lateralized by means of ITD. This allowed for testing whether the effects of a preceding sound were location- or cue-specific. Preceding sounds and target sounds were randomly paired across trials. Listeners had to discriminate whether they perceived the target sounds as coming fr... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3121302 Wed, 23 Dec 2009 22:33:45 +0100 3121302 http://www.medworm.com/index.php?rid=3121303&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ffu3h62423m274047%2F This study shows that electrically evoked auditory steady state responses (EASSRs) to low-rate pulse trains can be reliably recorded by electrodes placed on the scalp of a cochlear implant (CI) user and separated from the artifacts generated by the electrical stimulation. Response properties are described, and the predictive value of EASSRs for behaviorally hearing thresholds is analyzed. For six users of a Cochlear Nucleus CI, EASSRs to symmetric biphasic pulse trains with rates between 35 and 47 Hz were recorded with seven scalp electrodes. The influence of various stimulus parameters was assessed: pulse rate, stimulus intensity, monopolar or bipolar stimulation mode, and presentation of either one pulse train on one electrode or interleaved pulse trains with different pulse ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3121303 Wed, 23 Dec 2009 22:33:41 +0100 3121303 http://www.medworm.com/index.php?rid=3121304&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fn266852227174080%2F Abstract  This paper describes results from a stochastic computational neuron model that simulates the effects of rate adaptation on the responses to electrical stimulation in the form of pulse trains. We recently reported results from a single-node computational model that included a novel element that tracks external potassium ion concentration so as to modify membrane voltage and cause adaptation-like responses. Here, we report on an improved version of the model that incorporates the anatomical components of a complete feline auditory nerve fiber (ANF) so that conduction velocity and effects of manipulating the site of excitation can be evaluated. Model results demonstrate rate adaptation and changes in spike amplitude similar to those reported for feline ANFs. Changing... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3121304 Wed, 23 Dec 2009 22:33:36 +0100 3121304 http://www.medworm.com/index.php?rid=3054190&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fuh0477413j0mg187%2F We report a precise, simple, and accessible method of mathematically measuring and modeling the three-dimensional (3D) geometry of semicircular canals (SCCs) in living humans. Knowledge of this geometry helps understand the development and physiology of SCC stimulation. We developed a framework of robust techniques that automatically and accurately reconstruct SCC geometry from computed tomography (CT) images and are directly validated using micro-CT as ground truth. This framework measures the 3D centroid paths of the bony SCCs allowing direct comparison and analysis between ears within and between subjects. An average set of SCC morphology is calculated from 34 human ears, within which other geometrical attributes such as nonplanarity, radius of curvature, and inter-SCC angle are e... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3054190 Tue, 01 Dec 2009 08:30:37 +0100 3054190 http://www.medworm.com/index.php?rid=3020350&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fe363749205647w54%2F Abstract  The role of innate immunity and macrophage recruitment to the inner ear after hair cell injury is a subject where little is known. In this paper, we demonstrate recruitment of monocytes and macrophages to the inner ear after kanamycin. We also examined the effect of fractalkine receptor (CX3CR1) deletion in kanamycin ototoxicity. We observed more functional and structural damage in CX3CR1 null mice compared to wild-type and heterozygous littermates. In order to determine if increased susceptibility to kanamycin resulted from CX3CR1 deletion from cochlear leukocytes, we created bone marrow chimeras by transplanting CX3CR1-null bone marrow into wild-type mice whose native bone marrow was ablated by lethal irradiation. These mice were then treated with kanamycin sulf... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3020350 Sat, 21 Nov 2009 09:49:56 +0100 3020350 http://www.medworm.com/index.php?rid=3010005&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fghv87880524xw374%2F Abstract  Responses to tones with frequency ≤ 5 kHz were recorded from auditory nerve fibers (ANFs) of anesthetized chinchillas. With increasing stimulus level, discharge rate–frequency functions shift toward higher and lower frequencies, respectively, for ANFs with characteristic frequencies (CFs) lower and higher than ∼0.9 kHz. With increasing frequency separation from CF, rate–level functions are less steep and/or saturate at lower rates than at CF, indicating a CF-specific nonlinearity. The strength of phase locking has lower high-frequency cutoffs for CFs >4 kHz than for CFs < 3 kHz. Phase–frequency functions of ANFs with CFs lower and higher than ∼0.9 kHz have inflections, respectively, at frequencies higher and lower ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=3010005 Tue, 17 Nov 2009 23:39:38 +0100 3010005 http://www.medworm.com/index.php?rid=2982722&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F2u16375ul270161l%2F Abstract  Previous studies have shown that residual acoustic hearing supplements cochlear implant function to improve speech recognition in noise as well as perception of music. The current study had two primary objectives. First, we sought to determine how cochlear implantation and electrical stimulation over a time period of 14 to 21 months influence cochlear structures such as hair cells and spiral ganglion neurons. Second, we sought to investigate whether the structures that provide acoustic hearing also affect the perception of electrical stimulation. We compared psychophysical responses to cochlear implant stimulation in two groups of adult guinea pigs. Group I (11 animals) received a cochlear implant in a previously untreated ear, while group II (ten animals) re... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2982722 Tue, 10 Nov 2009 08:04:42 +0100 2982722 http://www.medworm.com/index.php?rid=2975134&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F7857835182812l51%2F Abstract  Glycosylation is a common post-translational modification of proteins and is implicated in a variety of cellular functions including protein folding, degradation, sorting and trafficking, and membrane protein recycling. The membrane protein prestin is an essential component of the membrane-based motor driving electromotility changes (electromotility) in the outer hair cell (OHC), a central process in auditory transduction. Prestin was earlier identified to possess two N-glycosylation sites (N163, N166) that, when mutated, marginally affect prestin nonlinear capacitance (NLC) function in cultured cells. Here, we show that the double mutant prestinNN163/166AA is not glycosylated and shows the expected NLC properties in the untreated and cholesterol-depleted HEK 293 c... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2975134 Sat, 07 Nov 2009 07:55:09 +0100 2975134 http://www.medworm.com/index.php?rid=2906340&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fl88354k622327033%2F Abstract  The middle ear is too complex a system for its function to be fully understood with simple descriptive models. Realistic mathematical models must be used in which structural elements are represented by geometrically correct three-dimensional (3D) models with correct physical parameters and boundary conditions. In the past, the choice of boundary conditions could not be based on experimental evidence as no clear-cut data were available. We have, therefore, studied the deformation of the tympanic membrane (TM) at its boundaries using X-ray microscopic computed tomography in human and gerbil while static pressure was applied to the ear canal. The 3D models of the TM and its bony attachments were carefully made and used to measure the deformation of the TM with focus ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2906340 Fri, 16 Oct 2009 06:19:32 +0100 2906340 http://www.medworm.com/index.php?rid=2906341&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fc370044505464gkw%2F Abstract  TRP genes encode a diverse family of ion channels which have been implicated in many sensory functions. Because several TRP channels have similar properties to the elusive hair cell transduction channel, recent attention has focused on TRP gene expression in the inner ear. At least four TRP genes are known to be expressed in hair cells: TRPC3, TRPV4, TRPA1, and TRPML3. However, there is little evidence supporting any of these as a component of the transduction complex. Other less well-characterized TRP channels are expressed in the inner ear, in particular, within the organ of Corti. Because of their potential role in sensory function, we investigated the developmental expression of RNA that encodes all 33 TRP subunits as well as several splice variants. We design... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2906341 Fri, 16 Oct 2009 06:19:23 +0100 2906341 http://www.medworm.com/index.php?rid=2896385&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm545203285555pp5%2F Abstract  A sudden increase in the amplitude of a component often causes its segregation from a complex tone, and shorter rise times enhance this effect. We explored whether this also occurs in implant listeners (n = 8). Condition 1 used a 3.5-s “complex tone” comprising concurrent stimulation on five electrodes distributed across the array of the Nucleus CI24 implant. For each listener, the baseline stimulus level on each electrode was set at 50% of the dynamic range (DR). Two 1-s increments of 12.5%, 25%, or 50% DR were introduced in succession on adjacent electrodes within the “inner” three of those activated. Both increments had rise and fall times of 30 and 970 ms or vice versa. Listeners reported which increment was higher in pitch. Some listeners... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2896385 Wed, 14 Oct 2009 05:45:10 +0100 2896385 http://www.medworm.com/index.php?rid=2884142&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ft2610v521722476n%2F Abstract  Recent studies indicate that supporting cells play important roles in inner ear development, function, and regeneration after injury, but the molecular mechanisms underlying these processes remain poorly understood. Inducible cell-specific gene recombination in supporting cells could be a powerful tool to study the roles of specific molecules in these cells. Here we tested the feasibility, effectiveness, and cell specificity of inducible Cre-mediated gene recombination in the postnatal inner ear using mice that express an inducible form of Cre (CreERT) under the transcriptional control of the proteolipid protein (PLP) promoter. We assessed the pattern of tamoxifen-induced gene recombination in the inner ear using the ROSA26-LacZ reporter line, in which the β-galac... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2884142 Sat, 10 Oct 2009 07:35:53 +0100 2884142 http://www.medworm.com/index.php?rid=2863916&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fp8m27547402256p5%2F Abstract  The effect of amplitude modulation of pulse trains on the loudness perceived by cochlear implantees was investigated for different overall levels of the signal, modulation depth and the carrier rate of the pulse train. Equally loud and threshold levels were determined for a variety of signal levels, modulation depths and carrier rates in six cochlear implantees. The pattern of results was consistent with the predictions of a previously published loudness model of McKay et al. (J Acoust Soc Am 113:2054–2063, 2003). The degree to which the loudness of modulated stimuli differed from the loudness elicited by an unmodulated pulse train with equivalent average current depended on the modulation depth and the absolute current level of the unmodulated stimulus. The eff... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2863916 Fri, 02 Oct 2009 05:47:08 +0100 2863916 http://www.medworm.com/index.php?rid=2863917&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Ff0478448k2v73t6n%2F Abstract  Evoked otoacoustic emissions are often used to study the medial olivocochlear (MOC) efferents in humans. There has been concern that the emission-evoking stimulus may itself elicit efferent activity and alter the evoked otoacoustic emission. Spontaneous otoacoustic emissions (SOAEs) are hence advantageous as no external stimulation is necessary to record the response in the test ear. Contralateral acoustic stimulation (CAS) has been shown to suppress SOAE level and elevate SOAE frequency, but the time course of these effects is largely unknown. By utilizing the Choi–Williams distribution, here we report a gradual adaptation during the presence of CAS and an overshoot following CAS offset in both SOAE magnitude and frequency from six normal-hearing female human s... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2863917 Fri, 02 Oct 2009 05:47:06 +0100 2863917 http://www.medworm.com/index.php?rid=2833302&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fxr34q31267301906%2F Abstract  In the present study, a computational model of phoneme identification was applied to data from a previous study, wherein cochlear implant (CI) users’ adaption to a severely shifted frequency allocation map was assessed regularly over 3 months of continual use. This map provided more input filters below 1 kHz, but at the expense of introducing a downwards frequency shift of up to one octave in relation to the CI subjects’ clinical maps. At the end of the 3-month study period, it was unclear whether subjects’ asymptotic speech recognition performance represented a complete or partial adaptation. To clarify the matter, the computational model was applied to the CI subjects’ vowel identification data in order to estimate the degree of adaptation, and... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2833302 Wed, 23 Sep 2009 06:03:15 +0100 2833302 http://www.medworm.com/index.php?rid=2810896&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fg526j81311147ltp%2F Abstract  Comodulation masking release (CMR) has been attributed to auditory processing within one auditory channel (within-channel cues) and/or across several auditory channels (across-channel cues). The present flanking-band (FB) experiment—using a 25-Hz-wide on-frequency noise masker (OFM) centered at the signal frequency of 10 kHz and a single 25-Hz-wide noise FB—was designed to separate the amount of CMR due to within- and across-channel cues and to investigate the role of temporal cues on the size of within-channel CMR. The results demonstrated within-channel CMR in the Naval Medical Research Institute mouse, while no unambiguous evidence could be found for CMR occurring due to across-channel processing (i.e., “true CMR”). The amount of within-channel CMR... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2810896 Thu, 17 Sep 2009 23:29:03 +0100 2810896 http://www.medworm.com/index.php?rid=2810897&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fp408220345673k22%2F Abstract  Binaural signal detection in an NoSπ task relies on interaural disparities introduced by adding an antiphasic signal to diotic noise. What metric of interaural disparity best predicts performance? Some models use interaural correlation; others differentiate between dynamic interaural time differences (ITDs) and interaural level differences (ILDs) of the effective stimulus. To examine the relative contributions of ITDs and ILDs in binaural detection, we developed a novel signal processing technique that selectively degrades different aspects (potential cues) of binaural stimuli (e.g., only ITDs are scrambled). Degrading a particular cue will affect performance only if that cue is relevant to the binaural processing underlying detection. This selective scrambling t... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2810897 Thu, 17 Sep 2009 12:42:07 +0100 2810897 http://www.medworm.com/index.php?rid=2735817&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F3030k326779ul60x%2F Abstract  Normal-hearing (NH) listeners and hearing-impaired (HI) listeners detected and discriminated time-reversed harmonic complexes constructed of equal-amplitude harmonic components with fundamental frequencies (F0s) ranging from 50 to 800 Hz. Component starting phases were selected according to the positive and negative Schroeder-phase algorithms to produce within-period frequency sweeps with relatively flat temporal envelopes. Detection thresholds were not affected by component starting phases for either group of listeners. At presentation levels of 80 dB SPL, NH listeners could discriminate the two waveforms nearly perfectly when the F0s were less than 300–400 Hz but fell to chance performance for higher F0s. HI listeners performed significantly poo... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2735817 Tue, 25 Aug 2009 06:45:47 +0100 2735817 http://www.medworm.com/index.php?rid=2706548&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fq55p432317j10177%2F Abstract  The anatomy of the distal incus, including the lenticular process, was examined in histological sections from 270 normal cadaveric human temporal bones aged between less than 1 month and 100 years. All but nine of these sectioned specimens showed signs of a bony connection between the long process of the incus and the flattened plate of the lenticular process, and in 108 specimens a complete bony attachment was observed in a single 20 μm section. In these 108 ears, the bony lenticular process consisted of a proximal narrow “pedicle” connected to a distal flattened “plate” that forms the incudal component of the incudo-stapedial joint. A fibrous joint capsule extended from the stapes head to the pedicle of the lenticular process on all sides,... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2706548 Sat, 15 Aug 2009 09:01:15 +0100 2706548 http://www.medworm.com/index.php?rid=2683078&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fa387r42007n60742%2F Abstract  Despite the significant advances in language perception for cochlear implant (CI) recipients, music perception continues to be a major challenge for implant-mediated listening. Our understanding of the neural mechanisms that underlie successful implant listening remains limited. To our knowledge, this study represents the first neuroimaging investigation of music perception in CI users, with the hypothesis that CI subjects would demonstrate greater auditory cortical activation than normal hearing controls. H2 15O positron emission tomography (PET) was used here to assess auditory cortical activation patterns in ten postlingually deafened CI patients and ten normal hearing control subjects. Subjects were presented with language, melody, and rhythm tasks during sca... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2683078 Fri, 07 Aug 2009 10:54:18 +0100 2683078 http://www.medworm.com/index.php?rid=2661616&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fa32931875m2l8055%2F We examined the expression of several known support cell markers to investigate for possible support cell dedifferentiation in the damaged ears. The support cell markers investigated included the microtubule protein acetylated tubulin, the transcription factor Sox2, and the Notch signaling ligand Jagged1. Non-sensory epithelial cells remaining in the organ of Corti retain acetylated tubulin, Sox2 and Jagged1 expression, even when the epithelium has a monolayer-like appearance. These results suggest a lack of marked SC dedifferentiation in these aged and badly damaged ears. Content Type Journal ArticleDOI 10.1007/s10162-009-0183-xAuthors Elizabeth C. Oesterle, University of Washington Virginia Merrill Bloedel Hearing Research Center, Department of Otolaryngology-Head and Neck Surg... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2661616 Fri, 31 Jul 2009 08:48:40 +0100 2661616 http://www.medworm.com/index.php?rid=2651593&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fw84306j765u81604%2F Abstract  Otoferlin is involved in neurotransmitter release at the synapse between inner hair cells (IHCs) and auditory nerve fibres, and mutations in the OTOF gene result in severe to profound hearing loss. Abnormal sound-evoked cochlear potentials were recorded with transtympanic electrocochleography from four children with otoferlin (OTOF) mutations to evaluate physiological effects in humans of abnormal neurotransmitter release from IHCs. The subjects were profoundly deaf with absent auditory brainstem responses and preserved otoacoustic emissions consistent with auditory neuropathy. Two children were compound heterozygotes for mutations c.2732_2735dupAGCT and p.Ala964Glu; one subject was homozygous for mutation p.Phe1795Cys, and one was compound heterozygote for two nov... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2651593 Tue, 28 Jul 2009 06:14:54 +0100 2651593 http://www.medworm.com/index.php?rid=2642718&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm53t4641325015ht%2F Abstract  Forward masking by harmonic tone complexes was measured for on- and off-frequency maskers as a function of masker phase curvature for two masker durations (30 and 200 ms). For the lowest signal frequency (1 kHz), the results matched predictions based on the expected interactions between the phase curvature and amplitude compression of peripheral auditory filtering. For the higher signal frequencies (2 and 6 kHz), the data increasingly departed from predictions in two respects. First, the effects of the masker phase curvature became stronger with increasing masker duration, inconsistent with the expected effects of the fast-acting compression and time-invariant phase response of basilar membrane filtering. Second, significant effects of masker phase ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2642718 Fri, 24 Jul 2009 23:42:18 +0100 2642718 http://www.medworm.com/index.php?rid=2642719&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fv35064l822201680%2F Abstract  Acoustic activation of the vestibular system has been well documented in humans and animal models. In the past decade, sound-evoked myogenic potentials in the sternocleidomastoid muscle (cVEMP) and the extraocular muscles (oVEMP) have been extensively studied, and their potentials as new tests for vestibular function have been widely recognized. However, the extent to which sound activates the otolith and canal pathways remains controversial. In the present study, we examined this issue in a recently developed nonhuman primate model of acoustic activation of the vestibular system, i.e., sound-evoked vestibulo-ocular reflexes (VOR) in behaving monkeys. To determine whether the canal and otolith VOR pathways are activated by sound, we analyzed abducens neurons' resp... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2642719 Fri, 24 Jul 2009 23:42:15 +0100 2642719 http://www.medworm.com/index.php?rid=2478398&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F3740251553818236%2F Abstract  When two pure tones (or primaries) of slightly different frequencies (f 1 and f 2) are presented to the ear, new frequency components are generated by nonlinear interaction of the primaries within the cochlea. These new components can be recorded in the ear canal as otoacoustic emissions (OAE). The level of the 2f 1−f 2 OAE component is known as the distortion product otoacoustic emission (DPOAE) and is regarded as an indicator of the physiological state of the cochlea. The current view is that maximal level DPOAEs occur for primaries that produce equal excitation at the f 2 cochlear region, but this notion cannot be directly tested in living humans because it is impossible to record their cochlear responses while monitoring their ear canal DPOAE levels. On t... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2478398 Sat, 13 Jun 2009 07:48:20 +0100 2478398 http://www.medworm.com/index.php?rid=2478399&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fe1337h7322r767q3%2F Abstract  The outer hair cell (OHC) lateral plasma membrane houses the transmembrane protein prestin, a necessary component of the yet unknown molecular mechanism(s) underlying electromotility and the exquisite sensitivity and frequency selectivity of mammalian hearing. The importance of the plasma membrane environment in modulating OHC electromotility has been substantiated by recent studies demonstrating that membrane cholesterol alters prestin activity in a manner consistent with cholesterol-induced changes in auditory function. Cholesterol is known to affect membrane material properties, and measurements of lipid lateral mobility provide a method to asses these changes in living OHCs. Using fluorescence recovery after photobleaching (FRAP), we characterized regional dif... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2478399 Thu, 11 Jun 2009 13:50:44 +0100 2478399 http://www.medworm.com/index.php?rid=2478400&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F8836657r43t07232%2F Abstract  The dynamic displacement of the semicircular canal cupula and modulation of afferent nerve discharge were measured simultaneously in response to physiological stimuli in vivo. The adaptation time constant(s) of normal cupulae in response to step stimuli averaged 36 s, corresponding to a mechanical lower corner frequency for sinusoidal stimuli of 0.0044 Hz. For stimuli equivalent to 40–200 deg/s of angular head velocity, the displacement gain of the central region of the cupula averaged 53 nm per deg/s. Afferents adapted more rapidly than the cupula, demonstrating the presence of a relaxation process that contributes significantly to the neural representation of angular head motions by the discharge patterns of canal afferent neurons. We also i... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2478400 Wed, 10 Jun 2009 10:10:34 +0100 2478400 http://www.medworm.com/index.php?rid=2478401&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F0k51528027p43562%2F Abstract  Electrical interaural time delay (ITD) discrimination was measured using 300-ms bursts applied to binaural pitch matched electrodes at basal, mid, and apical locations in each ear. Six bilateral implant users, who had previously shown good ITD sensitivity at a pulse rate of 100 pulses per second (pps), were assessed. Thresholds were measured as a function of pulse rate between 100 and 1,000 Hz, as well as modulation rate over that same range for high-rate pulse trains at 6,000 pps. Results were similar for all three places of stimulation and showed decreasing ITD sensitivity as either pulse rate or modulation rate increased, although the extent of that effect varied across subjects. The results support a model comprising a common ITD mechanism for high- ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2478401 Wed, 10 Jun 2009 10:10:33 +0100 2478401 http://www.medworm.com/index.php?rid=2470526&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F43l1613861382626%2F Abstract  Processing dynamic changes in the stimulus stream is a major task for sensory systems. In the auditory system, an increase in the temporal integration window between the inferior colliculus (IC) and auditory cortex is well known for monaural signals such as amplitude modulation, but a similar increase with binaural signals has not been demonstrated. To examine the limits of binaural temporal processing at these brain levels, we used the binaural beat stimulus, which causes a fluctuating interaural phase difference, while recording from neurons in the unanesthetized rabbit. We found that the cutoff frequency for neural synchronization to the binaural beat frequency (BBF) decreased between the IC and auditory cortex, and that this decrease was associated with an inc... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2470526 Tue, 09 Jun 2009 15:33:09 +0100 2470526 http://www.medworm.com/index.php?rid=2460048&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Flw51n283022r1715%2F Abstract  Basilar membrane responses to clicks and to white noise were recorded using laser velocimetry at basal sites of the chinchilla cochlea with characteristic frequencies near 10 kHz. Responses to noise grew at compressive rates and their instantaneous frequencies decreased with increasing stimulus level. First-order Wiener kernels were computed by cross-correlation of the noise stimuli and the responses. For linear systems, first-order Wiener kernels are identical to unit impulse responses. In the case of basilar membrane responses, first-order Wiener kernels and responses to clicks measured at the same sites were similar but not identical. Both consisted of transient oscillations with onset frequencies which increased rapidly, over about 0.5 ms, from 4–5... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2460048 Thu, 04 Jun 2009 10:10:12 +0100 2460048 http://www.medworm.com/index.php?rid=2460047&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fvw6w26hmw0651801%2F Abstract  Modern cochlear implants utilize interleaved presentation of pulses on different electrodes to avoid physical interference among multiple current fields, yet neural interaction still exists. In the present study, masking was examined with four Nucleus24 users with the banded electrode array in an interleaved masking paradigm, where a probe stimulus was interleaved with a masker stimulus. Spatial and temporal aspects of masking were addressed by fixing the masker at the middle of the electrode array and changing the location of the probe and by testing various stimulation rates: 125, 500, 2,000, and 6,410 Hz. In addition, growth of masking (GOM) was assessed by changing the masker level in six steps. Results indicated that masking patterns were generally much ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2460047 Thu, 04 Jun 2009 10:10:12 +0100 2460047 http://www.medworm.com/index.php?rid=2460049&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fc721r710v8634245%2F Abstract  The basilar papilla (BP) in the frog inner ear is a relatively simple auditory receptor. Its hair cells are embedded in a stiff support structure, with the stereovilli connecting to a flexible tectorial membrane (TM). Acoustic energy passing the papilla presumably causes displacement of the TM, which in turn deflects the stereovilli and stimulates the hair cells. Auditory neurons that contact the BP’s hair cells are known to have nearly identical characteristic frequencies and frequency selectivity. In this paper, we present optical measurements of the mechanical response of the TM. Results were obtained from five specimens. The TM displacement was essentially in phase across the membrane, with the largest amplitudes occurring near the hair cells. The response w... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2460049 Tue, 02 Jun 2009 08:09:09 +0100 2460049 http://www.medworm.com/index.php?rid=2425193&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F84077436861771m0%2F Abstract  Efferent inhibition of cochlear hair cells is mediated by α9α10 nicotinic cholinergic receptors (nAChRs) functionally coupled to calcium-activated, small conductance (SK2) potassium channels. Before the onset of hearing, efferent fibers transiently make functional cholinergic synapses with inner hair cells (IHCs). The retraction of these fibers after the onset of hearing correlates with the cessation of transcription of the Chrna10 (but not the Chrna9) gene in IHCs. To further analyze this developmental change, we generated a transgenic mice whose IHCs constitutively express α10 into adulthood by expressing the α10 cDNA under the control of the Pou4f3 gene promoter. In situ hybridization showed that the α10 mRNA is expressed in IHCs of 8-week-old transgenic mic... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2425193 Tue, 19 May 2009 05:59:15 +0100 2425193 http://www.medworm.com/index.php?rid=2354900&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fu5281045xkg76733%2F In this study, we use Hes5-GFP transgenic mice and in situ hybridization to report the expression pattern of Hes5 in the inner ear. We find that Hes5 is expressed in the developing auditory epithelium of the cochlea beginning at embryonic day 14.5 (E14.5), becomes restricted to a particular subset of cochlear supporting cells, is downregulated in the postnatal cochlea, and is not present in adults. In the vestibular system, we detect Hes5 in developing supporting cells as early as E12.5 and find that Hes5 expression is maintained in some adult vestibular supporting cells. In order to determine the effect of hair cell damage on Notch signaling in the cochlea, we damaged cochlear hair cells of adult Hes5-GFP mice in vivo using injection of kanamycin and furosemide. Although outer ha... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2354900 Fri, 17 Apr 2009 07:23:23 +0100 2354900 http://www.medworm.com/index.php?rid=2333554&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fg832q01250471861%2F Abstract  Any sound can be separated mathematically into a slowly varying envelope and rapidly varying fine-structure component. This property has motivated numerous perceptual studies to understand the relative importance of each component for speech and music perception. Specialized acoustic stimuli, such as auditory chimaeras with the envelope of one sound and fine structure of another have been used to separate the perceptual roles for envelope and fine structure. Cochlear narrowband filtering limits the ability to isolate fine structure from envelope; however, envelope recovery from fine structure has been difficult to evaluate physiologically. To evaluate envelope recovery at the output of the cochlea, neural cross-correlation coefficients were developed that quantify... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2333554 Tue, 14 Apr 2009 05:48:36 +0100 2333554 http://www.medworm.com/index.php?rid=2333555&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2F02j62n6l32625770%2F In this study, the survival and functionality of SGCs were investigated after temporary treatment with brain-derived neurotrophic factor (BDNF). Guinea pigs in the experimental group were deafened, and 2 weeks later, the right cochleae were implanted with an electrode array and drug delivery cannula. BDNF was administered to the implanted cochleae during a 4-week period via a mini-osmotic pump. After completion of the treatment, the osmotic pumps were removed. Two weeks later, the animals were killed and the survival of SGCs was analyzed. To monitor the functionality of the auditory nerve, electrically evoked auditory brainstem responses (eABRs) were recorded in awake animals throughout the experiment. BDNF treatment resulted in enhanced survival of SGCs 2 weeks after cessa... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2333555 Tue, 14 Apr 2009 05:48:35 +0100 2333555 http://www.medworm.com/index.php?rid=2308689&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fd782029618442211%2F This study examined effects of histone deacetylases (HDACs), whose main function is to modify histone acetylation, on the regulation of regenerative proliferation in the chick utricle. Cultures of regenerating utricles and dissociated cells from the utricular sensory epithelia were treated with the HDAC inhibitors valproic acid, trichostatin A, sodium butyrate, and MS-275. All of these molecules prevent the enzymatic removal of acetyl groups from histones, thus maintaining nuclear chromatin in a “relaxed” (open) configuration. Treatment with all inhibitors resulted in comparable decreases in supporting cell proliferation. We also observed that treatment with the HDAC1-, 2-, and 3-specific inhibitor MS-275 was sufficient to reduce proliferation and that two class I HDACs—HDAC1 a... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2308689 Thu, 02 Apr 2009 05:55:20 +0100 2308689 http://www.medworm.com/index.php?rid=2308690&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fu815375236q84261%2F Abstract  At low stimulation rates, electrically stimulated auditory nerve fibers typically fire regularly, in lock-step to the applied stimulus. At high stimulation rates, however, these same fibers fire irregularly. Firing irregularity has been attributed to the random opening and closing of voltage-gated sodium channels at the spike generation site. We demonstrate, however, that the nonlinear dynamics of neural excitation and refractoriness embodied in the FitzHugh–Nagumo (FN) model produce realistic firing irregularity at high stimulus rates, even in the complete absence of ongoing physiological noise. Indeed, we show that ongoing noise can actually regularize the response at low discharge rates. The degree of stimulus-dependent irregularity is determined not so much ... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2308690 Tue, 24 Mar 2009 07:06:10 +0100 2308690 http://www.medworm.com/index.php?rid=2263359&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fn3711720vg062750%2F This report presents an animal model for type IV fibrocyte loss, along with immunocytochemical evidence that noise-induced loss of these cells may account for previously unexplained hearing losses. The remarkably low threshold for noise-induced loss of type IV fibrocytes, approximately 24 dB less than the threshold for adjacent hair cell destruction, may account for the prevalence of missing fibrocytes in humans. In mice, changes in the spectrum of traumatizing noise had little effect upon the site of loss of the fibrocytes, suggesting that the primary site of damage that induced the loss was the basal-most cochlear turn, a site expected to be damaged by all three noise bands. Type IV fibrocytes were found to immunostain for connective tissue growth factor (CTGF) and for transfo... JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2263359 Wed, 11 Mar 2009 14:09:36 +0100 2263359 http://www.medworm.com/index.php?rid=2263364&cid=s_33337_16_f&fid=33337&url=http%3A%2F%2Fwww.springerlink.com%2Fcontent%2Fm563022582050621%2F In conclusion, the similarity of octopus cells in mice and kittens suggests that the anatomical and biophysical specializations that allow octopus cells to detect and convey synchronous firing among auditory nerve fibers are common to all mammals. Content Type Journal ArticleDOI 10.1007/s10162-009-0159-xAuthors Ramazan Bal, Firat University Department of Biophysics, Faculty of Medicine 23119 Elazig TurkeyGiyasettin Baydas, Firat University Department of Physiology, Faculty of Medicine Elazig Turkey Journal JARO - Journal of the Association for Research in OtolaryngologyOnline ISSN 1438-7573Print ISSN 1525-3961 (Source: JARO - Journal of the Association for Research in Otolaryngology) JARO - Journal of the Association for Research in Otolaryngology journals http://www.medworm.com/rss/comments.php?id=2263364 Wed, 11 Mar 2009 14:09:33 +0100 2263364