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 'Journal of Neurophysiology' source. Wed, 08 Feb 2012 20:43:17 +0100 http://www.medworm.com/index.php?rid=5668750&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1247%3Frss%3D1 Adaptation of movement may be driven by the difference between planned and actual motor performance, or the difference between expected and actual sensory consequences of movement. To identify how the nervous system differentially uses these signals, we asked: does motor adaptation occur when movement errors are irrelevant to the task goal? Participants reached on a digitizing tablet from a fixed start location to one of three targets: a point, an arc, or a ray. For the arc, reaches could be in any direction, but to a specific extent. For the ray, reaches could be to any distance, but in a targeted direction. After baseline reaching to the point, the direction or extent of continuous visual feedback was perturbed during training with either a cursor rotation or gain, respectively, while re... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668750 Wed, 08 Feb 2012 05:00:00 +0100 5668750 http://www.medworm.com/index.php?rid=5668749&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1241%3Frss%3D1 To interact with the environment efficiently, the nervous system must generate expectations about redundant sensory signals and detect unexpected ones. Neural circuits can, for example, compare a prediction of the sensory signal that was generated by the nervous system with the incoming sensory input, to generate a response selective to novel stimuli. In the first-order electrosensory neurons of a gymnotiform electric fish, a negative image of low-frequency redundant communication signals is subtracted from the neural response via feedback, allowing unpredictable signals to be extracted. Here we show that the cancelling feedback not only suppresses the predictable signal but also actively enhances the response to the unpredictable communication signal. A transient mismatch between the pred... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668749 Wed, 08 Feb 2012 05:00:00 +0100 5668749 http://www.medworm.com/index.php?rid=5668748&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1230%3Frss%3D1 In this report we show that the passive stiffness of the wrist is sufficient to account for this pattern. Simulating the dynamics of wrist rotations using a demonstrably realistic model under a variety of conditions, we show that wrist stiffness can explain all characteristics of the observed pattern of curvature. We also provide evidence against other possible causes. We further demonstrate that the phenomenon is robust against variations in human wrist parameters (inertia, damping, and stiffness) and choice of model inputs. Our findings explain two previously observed phenomena: why faster wrist rotations exhibit more curvature and why path curvature rotates with pronation-supination of the forearm. Our results imply that, as in reaching, path straightness is a goal in the planning and c... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668748 Wed, 08 Feb 2012 05:00:00 +0100 5668748 http://www.medworm.com/index.php?rid=5668747&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1222%3Frss%3D1 Training rats to perform rapidly and efficiently in an olfactory discrimination task results in robust enhancement of excitatory and inhibitory synaptic connectivity in the rat piriform cortex, which is maintained for days after training. To explore the mechanisms by which such synaptic enhancement occurs, we recorded spontaneous miniature excitatory and inhibitory synaptic events in identified piriform cortex neurons from odor-trained, pseudo-trained, and naive rats. We show that olfactory discrimination learning induces profound enhancement in the averaged amplitude of AMPA receptor-mediated miniature synaptic events in piriform cortex pyramidal neurons. Such physiological modifications are apparent at least 4 days after learning completion and outlast learning-induced modifications in t... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668747 Wed, 08 Feb 2012 05:00:00 +0100 5668747 http://www.medworm.com/index.php?rid=5668746&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1210%3Frss%3D1 The rostral ventromedial medulla (RVM) is part of descending circuitry that modulates nociceptive processing at the level of the spinal cord. RVM output can facilitate pain transmission under certain conditions such as inflammation, and thereby contribute to hyperalgesia. Evidence suggests that substance P and activation of neurokinin-1 (NK-1) receptors in the RVM are involved in descending facilitation of nociception. We showed previously that injection of NK-1 receptor antagonists into the RVM attenuated mechanical and heat hyperalgesia produced by intraplantar injection of capsaicin. Furthermore, intraplantar injection of capsaicin excited ON cells in the RVM and inhibited ongoing activity of OFF cells. In the present studies, we therefore examined changes in responses of RVM neurons to... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668746 Wed, 08 Feb 2012 05:00:00 +0100 5668746 http://www.medworm.com/index.php?rid=5668745&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1199%3Frss%3D1 This study reports the findings of two classes of corneal afferents excited by drying of the cornea (dry responses) in isoflurane-anesthetized rats: cold-sensitive (CS; 87%) and cold-insensitive (CI; 13%) neurons. Compared with CI neurons, CS neurons showed significantly higher firing rates over warmer corneal temperatures (~31–15°C) and greater responses to menthol, drying, and wetting of the cornea but lower responses when hyperosmolar solutions were applied to the ocular surface. We proposed that the dry responses of these corneal afferents derive from cooling and an increased osmolarity of the ocular surface, leading to the production of basal tears. An ocular application of the transient receptor potential channel TRPM8 antagonist BCTC (20 μM) decreased the dry responses ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668745 Wed, 08 Feb 2012 05:00:00 +0100 5668745 http://www.medworm.com/index.php?rid=5668744&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1186%3Frss%3D1 Neurons of the medial superior olive (MSO) code for the azimuthal location of low-frequency sound sources via a binaural coincidence detection system operating on microsecond time scales. These neurons are morphologically simple and stereotyped, and anatomical studies have indicated a functional segregation of excitatory and inhibitory inputs between cellular compartments. It is thought that this morphological arrangement holds important implications for the computational task of these cells. To date, however, there has been no functional investigation into synaptic input sites or functional receptor distributions on mature neurons of the MSO. Here, functional neurotransmitter receptor maps for amino-3-hydroxyl-5-methyl-4-isoxazole propionate (AMPA), N-methyl-d-aspartate (NMDA), glycine (G... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668744 Wed, 08 Feb 2012 05:00:00 +0100 5668744 http://www.medworm.com/index.php?rid=5668743&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1172%3Frss%3D1 The dorsal nucleus of the lateral lemniscus (DNLL) is an auditory brain stem structure that generates a long-lasting GABAergic output, which is important for binaural processing. Despite its importance in binaural processing, little is known about the cellular physiology and the synaptic input kinetics of DNLL neurons. To assess the relevant physiological parameters of DNLL neurons, their late postnatal developmental profile was analyzed in acute brain slices of 9- to 26-day-old Mongolian gerbils. The observed developmental changes in passive membrane and action potential (AP) properties all point toward an improvement of fast and precise signal integration in these neurons. Accordingly, synaptic glutamatergic and GABAergic current kinetics accelerate with age. The changes in intrinsic and... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668743 Wed, 08 Feb 2012 05:00:00 +0100 5668743 http://www.medworm.com/index.php?rid=5668742&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1164%3Frss%3D1 In this study, origins of the subcortical and cortical signals are explored by decomposing the evoked neuronal activities into short- and long-latency responses (SLR and LLR), respectively. We evaluated the effect of therapeutic hypothermia on SLR and LLR during early recovery from cardiac arrest (CA)-induced HI in a rodent model. Twelve rats were subjected to CA, after which half of them were treated with hypothermia (32–34°C) and the rest were kept at normal temperature (36–37°C). Evoked neuronal activities from the primary somatosensory cortex, including multiunit activity (MUA) and local field potential (LFP), were continuously recorded during injury and early recovery. Results showed that upon initiation of injury, LLR disappeared first, followed by the disappearan... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668742 Wed, 08 Feb 2012 05:00:00 +0100 5668742 http://www.medworm.com/index.php?rid=5668741&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1157%3Frss%3D1 We report that the activation of mGluR5, which are located on presynaptic dendrites of local interneurons, increases GABA output that in turn produces an increased inhibitory activity on proximal but not distal dendrites of dLGN thalamocortical neurons. In contrast, mGluR1 activation produces strong membrane depolarization in thalamocortical neurons regardless of distal or proximal dendritic locations. These findings provide physiological evidence that mGluR1 appear to be distributed along the thalamocortical neuron dendrites, whereas mGluR5-dependent action occurs on the proximal dendrites/soma of thalamocortical neurons. The differential distribution and activation of mGluR subtypes on interneurons and thalamocortical neurons may serve to shape excitatory synaptic integration and thereby... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668741 Wed, 08 Feb 2012 05:00:00 +0100 5668741 http://www.medworm.com/index.php?rid=5668740&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1142%3Frss%3D1 Experience-dependent changes in neural connectivity underlie developmental learning and result in life-long changes in behavior. In songbirds axons from the cortical region LMANcore (core region of lateral magnocellular nucleus of anterior nidopallium) convey the output of a basal ganglia circuit necessary for song learning to vocal motor cortex [robust nucleus of the arcopallium (RA)]. This axonal projection undergoes remodeling during the sensitive period for learning to achieve topographic organization. To examine how auditory experience instructs the development of connectivity in this pathway, we compared the morphology of individual LMANcore->RA axon arbors in normal juvenile songbirds to those raised in white noise. The spatial extent of axon arbors decreased during the first wee... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668740 Wed, 08 Feb 2012 05:00:00 +0100 5668740 http://www.medworm.com/index.php?rid=5668739&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1123%3Frss%3D1 Auditory cortical processing is thought to be accomplished along two processing streams. The existence of a posterior/dorsal stream dealing, among others, with the processing of spatial aspects of sound has been corroborated by numerous studies in several species. An anterior/ventral stream for the processing of nonspatial sound qualities, including the identification of sounds such as species-specific vocalizations, has also received much support. Originally discovered in anterolateral belt cortex, most recent work on the anterior/ventral pathway has been performed on far anterior superior temporal (ST) areas and on ventrolateral prefrontal cortex (VLPFC). Regions of the anterior/ventral stream near its origin in early auditory areas have been less explored. In the present study, we exami... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668739 Wed, 08 Feb 2012 05:00:00 +0100 5668739 http://www.medworm.com/index.php?rid=5668738&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1111%3Frss%3D1 Motor task variation has been shown to be a key ingredient in skill transfer, retention, and structural learning. However, many studies only compare training of randomly varying tasks to either blocked or null training, and it is not clear how experiencing different nonrandom temporal orderings of tasks might affect the learning process. Here we study learning in human subjects who experience the same set of visuomotor rotations, evenly spaced between –60° and +60°, either in a random order or in an order in which the rotation angle changed gradually. We compared subsequent learning of three test blocks of +30°->–30°->+30° rotations. The groups that underwent either random or gradual training showed significant (P < 0.01) facilitation of learning in... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668738 Wed, 08 Feb 2012 05:00:00 +0100 5668738 http://www.medworm.com/index.php?rid=5668737&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1094%3Frss%3D1 We used dynamic dense noise stimuli and local spectral reverse correlation methods to reveal the local sensitivities of neurons in visual area 2 (V2) of macaque monkeys to orientation and spatial frequency within their receptive fields. This minimized the potentially confounding assumptions that are inherent in stimulus selections. The majority of neurons exhibited a relatively high degree of homogeneity for the preferred orientations and spatial frequencies in the spatial matrix of facilitatory subfields. However, about 20% of all neurons showed maximum orientation differences between neighboring subfields that were greater than 25 deg. The neurons preferring horizontal or vertical orientations showed less inhomogeneity in space than the neurons preferring oblique orientations. Over 50% o... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668737 Wed, 08 Feb 2012 05:00:00 +0100 5668737 http://www.medworm.com/index.php?rid=5668736&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1080%3Frss%3D1 We examined multidigit control in 22 patients with cerebellar degeneration, 20 patients with cerebellar stroke, and 21 patients with surgical lesions after cerebellar tumor removal. In the first task, either the index finger or the middle finger was actively lifted from an object during static holding. Both controls and cerebellar patients increased the forces of the nearby digits in synchrony with lift-off to maintain the total finger force. Patients used increased finger forces but showed no significant deficits in the pattern and timing of rearrangement of finger forces. In the second task, subjects had to press and release one finger against a force-sensitive keypad with the other fingers being inactive. All patient groups showed increased force production of the noninstructed (enslave... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668736 Wed, 08 Feb 2012 05:00:00 +0100 5668736 http://www.medworm.com/index.php?rid=5668735&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1067%3Frss%3D1 Noise is a major concern in circuits processing electrical signals, including neural circuits. There are many factors that influence how noise propagates through neural circuits, and there are few systems in which noise levels have been studied throughout a processing pathway. We recorded intracellularly from multiple stages of a sensory-motor pathway in the locust that detects approaching objects. We found that responses are more variable and that signal-to-noise ratios (SNRs) are lower further from the sensory periphery. SNRs remain low even with the use of stimuli for which the pathway is most selective and for which the neuron representing its final sensory level must integrate many synaptic inputs. Modeling of this neuron shows that variability in the strength of individual synaptic i... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668735 Wed, 08 Feb 2012 05:00:00 +0100 5668735 http://www.medworm.com/index.php?rid=5668734&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1058%3Frss%3D1 CaMKII and PSD-95 are the two most abundant postsynaptic proteins in the postsynaptic density (PSD). Overexpression of either can dramatically increase synaptic strength and saturate long-term potentiation (LTP). To do so, CaMKII must be activated, but the same is not true for PSD-95; expressing wild-type PSD-95 is sufficient. This raises the question of whether PSD-95's effects are simply an equilibrium process [increasing the number of AMPA receptor (AMPAR) slots] or whether activity is somehow involved. To examine this question, we blocked activity in cultured hippocampal slices with TTX and found that the effects of PSD-95 overexpression were greatly reduced. We next studied the type of receptors involved. The effects of PSD-95 were prevented by antagonists of group I metabotropic glut... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668734 Wed, 08 Feb 2012 05:00:00 +0100 5668734 http://www.medworm.com/index.php?rid=5668733&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F4%2F1047%3Frss%3D1 The amygdala plays a central role in evaluating the significance of acoustic signals and coordinating the appropriate behavioral responses. To understand how amygdalar responses modulate auditory processing and drive emotional expression, we assessed how neurons respond to and encode information that is carried within complex acoustic stimuli. We characterized responses of single neurons in the lateral nucleus of the amygdala to social vocalizations and synthetic acoustic stimuli in awake big brown bats. Neurons typically responded to most of the social vocalizations presented (mean = nine of 11 vocalizations) but differentially modulated both firing rate and response duration. Surprisingly, response duration provided substantially more information about vocalizations than did spike rate. ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5668733 Wed, 08 Feb 2012 05:00:00 +0100 5668733 http://www.medworm.com/index.php?rid=5599464&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Ffull%2F107%2F3%2F1045%3Frss%3D1 (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599464 Mon, 16 Jan 2012 05:00:00 +0100 5599464 http://www.medworm.com/index.php?rid=5599461&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F1032%3Frss%3D1 Cortical spreading depression (CSD) is a consequence of a slowly propagating wave of neuronal and glial depolarization (spreading depolarization; SD). Massive release of glutamate contributes to SD propagation, and it was recently shown that Zn2+ is also released from synaptic vesicles during SD. The present study examined consequences of extracellular Zn2+ accumulation on the propagation of SD. SD mechanisms were studied first in murine brain slices, using focal KCl applications as stimuli and making electrical and optical recordings in hippocampal area CA1. Elevating extracellular Zn2+ concentrations with exogenous ZnCl2 reduced SD propagation rates. Selective chelation of endogenous Zn2+ (using TPEN or CaEDTA) increased SD propagation rates, and these effects appeared due to chelation o... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599461 Mon, 16 Jan 2012 05:00:00 +0100 5599461 http://www.medworm.com/index.php?rid=5599460&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F1022%3Frss%3D1 Our laboratory previously reported that gastric activity is controlled by a robust GABAA receptor-mediated inhibition in the medial nucleus of the tractus solitarius (mNTS) (Herman et al. 2009), and that μ-opioid receptor activation inhibits gastric tone by suppression of this GABA signaling (Herman et al. 2010). These data raised two questions: 1) whether any of this inhibition was due to tonic GABAA receptor-mediated conductance in the mNTS; and 2) whether μ-opioid receptor activation suppressed both tonic and phasic GABA signaling. In whole cell recordings from rat mNTS neurons, application of three GABAA receptor antagonists (gabazine, bicuculline, and picrotoxin) produced a persistent reduction in holding current and decrease in population variance or root mean square (RMS) nois... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599460 Mon, 16 Jan 2012 05:00:00 +0100 5599460 http://www.medworm.com/index.php?rid=5599459&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F1009%3Frss%3D1 ATP signaling to neurons and glia in the nervous system occurs via activation of both P2Y and P2X receptors. Here, we investigated the effects of P2Y1 receptor stimulation in developing striatal medium-sized neurons using patch-clamp recordings from acute brain slices of 7- and 28-day-old rats. Application of the selective P2Y1 receptor agonist 2-(Methylthio) ADP trisodium salt (2-MeSADP; 250 nM) increased outward K+ currents evoked by a ramp depolarization protocol in voltage-clamp recordings. This effect was observed in 59 out of 82 cells (72%) and was blocked completely by the P2Y1 antagonist, 2'-deoxy-N6-methyl adenosine 3',5'-diphosphate. The averaged 2-MeSADP-sensitive conductance was fitted by the sum of a linear conductance and a Boltzmann relation, giving one-half activation volta... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599459 Mon, 16 Jan 2012 05:00:00 +0100 5599459 http://www.medworm.com/index.php?rid=5599458&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F995%3Frss%3D1 The macaque anterior intraparietal area (AIP) is crucial for visually guided grasping. AIP neurons respond during the visual presentation of real-world objects and encode the depth profile of disparity-defined curved surfaces. We investigated the neural representation of curved surfaces in AIP using a stimulus-reduction approach. The stimuli consisted of three-dimensional (3-D) shapes curved along the horizontal axis, the vertical axis, or both the horizontal and the vertical axes of the shape. The depth profile was defined solely by binocular disparity that varied along either the boundary or the surface of the shape or along both the boundary and the surface of the shape. The majority of AIP neurons were selective for curved boundaries along the horizontal or the vertical axis, and neura... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599458 Mon, 16 Jan 2012 05:00:00 +0100 5599458 http://www.medworm.com/index.php?rid=5599457&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F984%3Frss%3D1 It has been noted that the power spectrum of intracortical local field potential (LFP) often scales as 1/f–2. It is thought that LFP mostly represents the spiking-related neuronal activity such as synaptic currents and spikes in the vicinity of the recording electrode, but no 1/f2 scaling is detected in the spike power. Although tissue filtering or modulation of spiking activity by UP and DOWN states could account for the observed LFP scaling, there is no consensus as to how it arises. We addressed this question by recording simultaneously LFP and single neurons ("single units") from multiple sites in somatosensory cortex of anesthetized rats. Single-unit data revealed the presence of periods of high activity, presumably corresponding to the "UP" states when the neuronal membrane pot... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599457 Mon, 16 Jan 2012 05:00:00 +0100 5599457 http://www.medworm.com/index.php?rid=5599456&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F973%3Frss%3D1 How the brain processes signals in the presence of noise impacts much of behavioral neuroscience. Thresholds provide one way to assay noise. While perceptual thresholds have been widely investigated, vestibuloocular reflex (VOR) thresholds have seldom been studied and VOR threshold dynamics have never, to our knowledge, been reported. Therefore, we assessed VOR thresholds as a function of frequency. Specifically, we measured horizontal VOR thresholds evoked by yaw rotation in rhesus monkeys, using standard signal detection approaches like those used in earlier human vestibular perceptual threshold studies. We measured VOR thresholds ranging between 0.21 and 0.76°/s; the VOR thresholds increased slightly with frequency across the measured frequency range (0.2–3 Hz). These results ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599456 Mon, 16 Jan 2012 05:00:00 +0100 5599456 http://www.medworm.com/index.php?rid=5599455&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F966%3Frss%3D1 Paired-pulse transcranial magnetic stimulation (ppTMS) is a safe and noninvasive tool for measuring cortical inhibition in humans, particularly in patients with disorders of cortical inhibition such as epilepsy. However, ppTMS protocols in rodent disease models, where mechanistic insight into the ppTMS physiology and into disease processes may be obtained, have been limited due to the requirement for anesthesia and needle electromyography. To eliminate the confounding factor of anesthesia and to approximate human ppTMS protocols in awake rats, we adapted the mechanomyogram (MMG) method to investigate the ppTMS inhibitory phenomenon in awake rats and then applied differential pharmacology to test the hypothesis that long-interval cortical inhibition is mediated by the GABAA receptor. Bilate... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599455 Mon, 16 Jan 2012 05:00:00 +0100 5599455 http://www.medworm.com/index.php?rid=5599454&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F958%3Frss%3D1 We investigated the influence of nociceptive stimulation on the accuracy of task execution and motor unit spike trains during low-force isometric contractions. Muscle pain was induced by infusion of hypertonic saline into the abductor digiti minimi muscle of 11 healthy men. Intramuscular EMG signals were recorded from the same muscle during four isometric contractions of 60-s duration at 10% of the maximal force [maximal voluntary contraction (MVC)] performed before injection (baseline), after injection of isotonic (control) or hypertonic saline (pain), and 15 min after pain was no longer reported. Each contraction was preceded by three 3-s ramp contractions from 0% to 10% MVC. The low-frequency oscillations of motor unit spike trains were analyzed by the first principal component of the l... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599454 Mon, 16 Jan 2012 05:00:00 +0100 5599454 http://www.medworm.com/index.php?rid=5599453&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F948%3Frss%3D1 In darkness, glutamate released from photoreceptors activates the metabotropic glutamate receptor 6 (mGluR6) on retinal ON bipolar cells. This activates the G protein Go, which then closes transient receptor potential melastatin 1 (TRPM1) channels, leading to cells' hyperpolarization. It has been generally assumed that deleting mGluR6 would render the cascade inactive and the ON bipolar cells constitutively depolarized. Here we show that the rod bipolar cells in mGluR6-null mice were hyperpolarized. The slope conductance of the current-voltage curves and the current noise were smaller than in wild type. Furthermore, while in wild-type rod bipolar cells, TRPM1 could be activated by local application of capsaicin; in null cells, it did not. These results suggest that the TRPM1 channel in mGl... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599453 Mon, 16 Jan 2012 05:00:00 +0100 5599453 http://www.medworm.com/index.php?rid=5599452&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F937%3Frss%3D1 In this study, we first characterized the maturation of cortical inhibitory synapse function from just before the onset of hearing through adulthood. We then examined the long-term effects of developmental conductive hearing loss (CHL). Whole cell recordings from gerbil thalamocortical brain slices revealed a significant decrease in the decay time of inhibitory currents during the first 3 mo of normal development. When assessed in adults, developmental CHL led to an enduring decrease of inhibitory synaptic strength, whereas the maturation of synaptic decay time was only delayed. Early CHL also depressed the maximum discharge rate of fast-spiking, but not low-threshold-spiking, inhibitory interneurons. We then asked whether adult onset CHL had a similar effect, but neither inhibitory curren... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599452 Mon, 16 Jan 2012 05:00:00 +0100 5599452 http://www.medworm.com/index.php?rid=5599451&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F923%3Frss%3D1 We studied the relative accuracy of drifting gratings and noise stimuli for functionally characterizing neural populations using two-photon calcium imaging. Calcium imaging has the potential to distort measurements due to nonlinearity in the conversion from spikes to observed fluorescence. We demonstrate a dramatic impact of fluorescence saturation on functional measurements in ferret V1 by showing that responses to drifting gratings strongly violate contrast invariance of orientation tuning, a fundamental property of the spike rates. The observed relationship is consistent with saturation that clips the high-contrast tuning curve peaks by ~40%. The nonlinearity was also apparent in mouse V1 responses to drifting gratings, but not as strong as in the ferret. Contrast invariance holds, howe... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599451 Mon, 16 Jan 2012 05:00:00 +0100 5599451 http://www.medworm.com/index.php?rid=5599450&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F913%3Frss%3D1 The cellular proteins that underlie mechanosensation remain largely enigmatic in mammalian systems. Mechanically sensitive ion channels are thought to distinguish pressure, stretch, and other types of tactile signals in skin. Transient receptor potential canonical 1 (TRPC1) is a candidate mechanically sensitive channel that is expressed in primary afferent sensory neurons. However, its role in the mechanical sensitivity of these neurons is unclear. Here, we investigated TRPC1-dependent responses to both innocuous and noxious mechanical force. Mechanically evoked action potentials in cutaneous myelinated A-fiber and unmyelinated C-fiber neurons were quantified using the ex vivo skin-nerve preparation to record from the saphenous nerve, which terminates in the dorsal hairy skin of the hindpa... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599450 Mon, 16 Jan 2012 05:00:00 +0100 5599450 http://www.medworm.com/index.php?rid=5599449&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F902%3Frss%3D1 Long-term potentiation (LTP) is a form of synaptic plasticity thought to underlie memory; thus knowing its developmental profile is fundamental to understanding function. Like memory, LTP has multiple phases with distinct timing and mechanisms. The late phase of LTP (L-LTP), lasting longer than 3 h, is protein synthesis dependent and involves changes in the structure and content of dendritic spines, the major sites of excitatory synapses. In previous work, tetanic stimulation first produced L-LTP at postnatal day 15 (P15) in area CA1 of rat hippocampus. Here we used a more robust induction paradigm involving theta-burst stimulation (TBS) in acute slices and found the developmental onset of L-LTP to be 3 days earlier at P12. In contrast, at P8–11, TBS only reversed the synaptic depres... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599449 Mon, 16 Jan 2012 05:00:00 +0100 5599449 http://www.medworm.com/index.php?rid=5599448&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F890%3Frss%3D1 Optimal feedback control postulates that feedback responses depend on the task relevance of any perturbations. We test this prediction in a bimanual task, conceptually similar to balancing a laden tray, in which each hand could be perturbed up or down. Single-limb mechanical perturbations produced long-latency reflex responses ("rapid motor responses") in the contralateral limb of appropriate direction and magnitude to maintain the tray horizontal. During bimanual perturbations, rapid motor responses modulated appropriately depending on the extent to which perturbations affected tray orientation. Specifically, despite receiving the same mechanical perturbation causing muscle stretch, the strongest responses were produced when the contralateral arm was perturbed in the opposite direction (l... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599448 Mon, 16 Jan 2012 05:00:00 +0100 5599448 http://www.medworm.com/index.php?rid=5599447&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F880%3Frss%3D1 Electrical stimulation of the median nerve at the wrist may elicit a blink reflex [hand blink reflex (HBR)] mediated by a neural circuit at brain stem level. As, in a Sherringtonian sense, the blink reflex is a defensive response, in a series of experiments we tested, in healthy volunteers, whether and how the HBR is modulated by the proximity of the stimulated hand to the face. Electromyographic activity was recorded from the orbicularis oculi, bilaterally. We observed that the HBR is enhanced when the stimulated hand is inside the peripersonal space of the face, compared with when it is outside, irrespective of whether the proximity of the hand to the face is manipulated by changing the position of the arm (experiment 1) or by rotating the head while keeping the arm position constant (ex... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599447 Mon, 16 Jan 2012 05:00:00 +0100 5599447 http://www.medworm.com/index.php?rid=5599446&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F868%3Frss%3D1 Extracellular H+ has been hypothesized to mediate feedback inhibition from horizontal cells onto vertebrate photoreceptors. According to this hypothesis, depolarization of horizontal cells should induce extracellular acidification adjacent to the cell membrane. Experiments testing this hypothesis have produced conflicting results. Studies examining carp and goldfish horizontal cells loaded with the pH-sensitive dye 5-hexadecanoylaminofluorescein (HAF) reported an extracellular acidification on depolarization by glutamate or potassium. However, investigations using H+-selective microelectrodes report an extracellular alkalinization on depolarization of skate and catfish horizontal cells. These studies differed in the species and extracellular pH buffer used and the presence or absence of co... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599446 Mon, 16 Jan 2012 05:00:00 +0100 5599446 http://www.medworm.com/index.php?rid=5599445&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F859%3Frss%3D1 Previous research demonstrates that our apparent mental flexibility depends largely on the strength of our prior intention; changing our intention in advance enables a smooth transition from one task to another (e.g., Astle DE, Jackson GM, Swainson R. J Cogn Neurosci 20: 255–267, 2008; Duncan J, Emslie H, Williams P, Johnson R, Freer C. Cogn Psychol 30: 257–303, 1996; Husain M, Parton A, Hodgson TL, Mort D, Rees G. Nat Neurosci 6: 117–118, 2003). However, these necessarily rapid anticipatory mechanisms have been difficult to study in the human brain. We used EEG and magnetoencephalography, specifically event-related potentials and fields (ERPs and ERFs), respectively, to explore the neural correlates of this important aspect of mental flexibility. Subjects performed a man... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599445 Mon, 16 Jan 2012 05:00:00 +0100 5599445 http://www.medworm.com/index.php?rid=5599444&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F850%3Frss%3D1 There are many cellular and synaptic mechanisms of plasticity in the vertebrate cortex. How the patterns of suprathreshold spiking activity in a population of neurons change because of this plasticity, however, has hardly been subjected to experimental studies. Here, we measured how evoked patterns of suprathreshold spiking activity in a cortical network were modified by cortical plasticity with single-cell and single-spike resolution. To record patterns of activity in the rodent barrel cortex, we used optical methods to detect suprathreshold activity from up to 40 neurons simultaneously. Pairing of two inputs resulted in a long-lasting modification of the cortical responses evoked by one of the inputs. The results indicate that plasticity rules on the network level inherit properties from... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599444 Mon, 16 Jan 2012 05:00:00 +0100 5599444 http://www.medworm.com/index.php?rid=5599443&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F836%3Frss%3D1 The spiking activity in the parietal reach region (PRR) represents the spatial goal of an impending reach when the reach is directed toward or away from a visual object. The local field potentials (LFPs) in this region also represent the reach goal when the reach is directed to a visual object. Thus PRR is a candidate area for reading out a patient's intended reach goals for neural prosthetic applications. For natural behaviors, reach goals are not always based on the location of a visual object, e.g., playing the piano following sheet music or moving following verbal directions. So far it has not been directly tested whether and how PRR represents reach goals in such cognitive, nonlocational conditions, and knowing the encoding properties in various task conditions would help in designing... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599443 Mon, 16 Jan 2012 05:00:00 +0100 5599443 http://www.medworm.com/index.php?rid=5599442&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F824%3Frss%3D1 Because of the availability of disease and genetic models, the mouse has become a valuable species for auditory neuroscience that will facilitate long-term goals of understanding neuronal mechanisms underlying the perception and processing of sounds. The goal of this study was to define the basic sound-evoked response properties of single neurons in the mouse dorsal cochlear nucleus (DCN). Neurons producing complex spikes were distinguished as cartwheel cells (CWCs), and other neurons were classified according to the response map scheme previously developed in DCN. Similar to observations in other rodent species, neurons of the mouse DCN exhibit relatively little sound-driven inhibition. As a result, type III was the most commonly observed response. Our findings are generally consistent wi... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599442 Mon, 16 Jan 2012 05:00:00 +0100 5599442 http://www.medworm.com/index.php?rid=5599441&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F808%3Frss%3D1 Motoneuron discharge patterns reflect the interaction of synaptic inputs with intrinsic conductances. Recent work has focused on the contribution of conductances mediating persistent inward currents (PICs), which amplify and prolong the effects of synaptic inputs on motoneuron discharge. Certain features of human motor unit discharge are thought to reflect a relatively stereotyped activation of PICs by excitatory synaptic inputs; these features include rate saturation and de-recruitment at a lower level of net excitation than that required for recruitment. However, PIC activation is also influenced by the pattern and spatial distribution of inhibitory inputs that are activated concurrently with excitatory inputs. To estimate the potential contributions of PIC activation and synaptic input ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599441 Mon, 16 Jan 2012 05:00:00 +0100 5599441 http://www.medworm.com/index.php?rid=5599440&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F796%3Frss%3D1 Oscillatory activity plays a crucial role in corticospinal control of muscle synergies and is widely investigated using corticospinal and intermuscular synchronization. However, the neurophysiological mechanisms that translate these rhythmic patterns into surface electromyography (EMG) are not well understood. This is underscored by the ongoing debate on the rectification of surface EMG before spectral analysis. Whereas empirical studies commonly rectify surface EMG, computational approaches have argued against it. In the present study, we employ a computational model to investigate the role of the motor unit action potential (MAUP) on the translation of oscillatory activity. That is, diverse MUAP shapes may distort the transfer of common input into surface EMG. We test this in a computati... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599440 Mon, 16 Jan 2012 05:00:00 +0100 5599440 http://www.medworm.com/index.php?rid=5599439&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F785%3Frss%3D1 In this study, we investigated whether eye position affects activity in both the central and shell regions. Accordingly, we mapped the location of eye position-sensitive neurons in six monkeys making spontaneous eye movements by sampling multiunit activity at regularly spaced intervals throughout the IC. We used a functional map based on auditory response patterns to estimate the anatomical location of recordings, in conjunction with structural MRI and histology. We found eye position-sensitive sites throughout the IC, including at 27% of sites in tonotopically organized recording penetrations (putatively the central nucleus). Recordings from surrounding tissue showed a larger proportion of sites indicating an influence of eye position (33–43%). When present, the magnitude of the cha... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599439 Mon, 16 Jan 2012 05:00:00 +0100 5599439 http://www.medworm.com/index.php?rid=5599438&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F772%3Frss%3D1 The parafascicular nucleus (Pf) receives cholinergic input from the pedunculopontine nucleus, part of the reticular activating system involved in waking and rapid eye movement (REM) sleep, and sends projections to the cortex. We tested the hypothesis that Pf neurons fire maximally at gamma band frequency (30–90 Hz), that this mechanism involves high-threshold voltage-dependent P/Q- and N-type calcium channels, and that this activity is enhanced by the cholinergic agonist carbachol (CAR). Patch-clamped 9- to 25-day-old rat Pf neurons (n = 299) manifested a firing frequency plateau at gamma band when maximally activated (31.5 ± 1.5 Hz) and showed gamma oscillations when voltage-clamped at holding potentials above –20 mV, and the frequency of the oscillations increased sign... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599438 Mon, 16 Jan 2012 05:00:00 +0100 5599438 http://www.medworm.com/index.php?rid=5599437&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F766%3Frss%3D1 To intercept or avoid moving objects successfully, we must compensate for the sensorimotor delays associated with visual processing and motor movement. Although straightforward in the case of constant velocity motion, it is unclear how humans compensate for accelerations, as our visual system is relatively poor at detecting changes in velocity. Work on free-falling objects suggests that we are able to predict the effects of gravity, but this represents the most simple, limiting case in which acceleration is constant and motion linear. Here, we show that an internal model also predicts the effects of complex, varying accelerations when they result from lawful interactions with the environment. Participants timed their responses with the arrival of a ball rolling within a tube of various sha... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599437 Mon, 16 Jan 2012 05:00:00 +0100 5599437 http://www.medworm.com/index.php?rid=5599436&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F758%3Frss%3D1 To understand how activity in mammalian neural circuits controls behavior, the mouse is a promising model system due to the convergence of genetic, optical, and physiological methods. The ability to control and quantify behavior precisely is also essential for these studies. We developed an operant visual detection paradigm to make visual psychophysical measurements: head-fixed mice make responses by pressing a lever. We designed this task to permit neurophysiological studies of behavior in cerebral cortex, where activity is variable from trial to trial and neurons encode many types of information simultaneously. To study neural responses in the face of this complexity, we trained mice to do a task where they perform hundreds of trials daily and perceptual thresholds can be measured. We us... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599436 Mon, 16 Jan 2012 05:00:00 +0100 5599436 http://www.medworm.com/index.php?rid=5599435&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F747%3Frss%3D1 Application of chondroitinase ABC (ChABC) to injured peripheral nerves improves axon regeneration, but it is not known whether functional recovery is also improved. Recordings of EMG activity [soleus (Sol) M response and H reflexes] evoked by nerve stimulation and of Sol and tibialis anterior (TA) EMG activity and hindlimb and foot kinematics during slope walking were made to determine whether ChABC treatment of the sciatic nerve at the time of transection improves functional recovery. Recovery of evoked EMG responses began as multiple small responses with a wide range of latencies that eventually coalesced into one or two more distinctive and consistent responses (the putative M response and the putative H reflex) in both groups. Both the initial evoked responses and the time course of th... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599435 Mon, 16 Jan 2012 05:00:00 +0100 5599435 http://www.medworm.com/index.php?rid=5599434&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F3%2F743%3Frss%3D1 Pitch perception is an important component of hearing, allowing us to appreciate melodies and harmonies as well as recognize prosodic cues in speech. Multiple studies over the last decade have suggested that pitch is represented by a pitch-processing center in auditory cortex. However, recent data (Barker D, Plack CJ, Hall DA. Cereb Cortex. In press; Hall DA, Plack CJ. Cereb Cortex 19: 576–585, 2009) now challenge these previous claims of a human "pitch center." (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5599434 Mon, 16 Jan 2012 05:00:00 +0100 5599434 http://www.medworm.com/index.php?rid=5562031&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F728%3Frss%3D1 The development of central nervous system slice preparations for electrophysiological studies has led to an explosion of knowledge of neuronal properties in health and disease. Studies of spinal motoneurons in these preparations, however, have been largely limited to the early postnatal period, as adult motoneurons are vulnerable to the insults sustained by the preparation. We therefore sought to develop an adult spinal cord slice preparation that permits recording from lumbar motoneurons. To accomplish this, we empirically optimized the composition of solutions used during preparation in order to limit energy failure, reduce harmful ionic fluxes, mitigate oxidative stress, and prevent excitotoxic cell death. In addition to other additives, this involved the use of ethyl pyruvate, which se... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562031 Wed, 04 Jan 2012 05:00:00 +0100 5562031 http://www.medworm.com/index.php?rid=5562030&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F718%3Frss%3D1 We report that in two identified neuronal types, three ionic currents are linearly correlated in a pairwise manner, suggesting their coexpression or direct interactions, under normal neuromodulatory conditions. In each cell, some currents remain correlated after neuromodulatory input is removed, whereas the correlations between the other pairs are either lost or altered. Interestingly, in each cell, a different suite of currents change their correlation. At the transcript level we observe distinct alterations in correlations between channel mRNA amounts, including one of the cell types lacking a correlation under normal neuromodulatory conditions and then gaining the correlation when neuromodulators are removed. Synaptic activity does not appear to contribute, with one possible exception, ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562030 Wed, 04 Jan 2012 05:00:00 +0100 5562030 http://www.medworm.com/index.php?rid=5562029&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F704%3Frss%3D1 Context-specific adaptation (Shelhamer M, Clendaniel R. Neurosci Lett 332: 200–204, 2002) explains that reflexive responses can be maintained with different "calibrations" for different situations (contexts). Which context cues are crucial and how they combine to evoke context-specific adaptation is not fully understood. Gaze stabilization in birds is a nice model with which to tackle that question. Previous data showed that when pigeons (Columba livia) were hung in a harness and subjected to a frontal airstream provoking a flying posture ("flying condition"), the working range of the optokinetic head response [optocollic reflex (OCR)] extended toward higher velocities compared with the "resting condition." The present study was aimed at identifying which context cues are instrumenta... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562029 Wed, 04 Jan 2012 05:00:00 +0100 5562029 http://www.medworm.com/index.php?rid=5562028&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F692%3Frss%3D1 In the nucleus accumbens (NAc), a medium spiny (MS) neuron receives GABAergic inputs from two major sources: fast-spiking (FS) neurons and other, adjacent MS neurons. These two types of inhibitory synapses are considered to play different roles in output activities, i.e., FS->MS connections suppress output from the NAc whereas MS->MS connections contribute to lateral inhibition. In the present study, we focused on the electrophysiological properties of unitary inhibitory postsynaptic currents (uIPSCs) obtained from MS->MS connections and FS->MS connections and examined the effects of quinpirole, a dopamine D2-like receptor agonist, on uIPSCs with multiple whole cell patch-clamp recording. Application of quinpirole (1 μM) reliably suppressed the amplitude of uIPSCs by 29.6% i... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562028 Wed, 04 Jan 2012 05:00:00 +0100 5562028 http://www.medworm.com/index.php?rid=5562027&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F677%3Frss%3D1 The R6/2 mouse is the most frequently used model for experimental and preclinical drug trials in Huntington's disease (HD). When the R6/2 mouse was first developed, it carried exon 1 of the huntingtin gene with ~150 cytosine-adenine-guanine (CAG) repeats. The model presented with a rapid and aggressive phenotype that shared many features with the human condition and was particularly similar to juvenile HD. However, instability in the CAG repeat length due to different breeding practices has led to both decreases and increases in average CAG repeat lengths among colonies. Given the inverse relationship in human HD between CAG repeat length and age at onset and to a degree, the direct relationship with severity of disease, we have investigated the effect of altered CAG repeat length. Four li... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562027 Wed, 04 Jan 2012 05:00:00 +0100 5562027 http://www.medworm.com/index.php?rid=5562026&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F666%3Frss%3D1 In this study, we tested whether, during human quiet standing, the force of the medial gastrocnemius (MG) muscle is predominantly controlled by recruitment or rate coding. If MG control during standing was mainly due to recruitment, then we further asked what the trigger mechanism is. Is it determined internally, or is it related to body kinematics? While seven healthy subjects stood quietly, intramuscular electromyograms were recorded from the MG muscle with three pairs of wire electrodes. The number of active motor units and their mean discharge rate were compared for different sway velocities and positions. Motor unit discharges occurred more frequently when the body swayed faster and forward (Pearson R = 0.63; P < 0.0001). This higher likelihood of observing motor unit potentials wa... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562026 Wed, 04 Jan 2012 05:00:00 +0100 5562026 http://www.medworm.com/index.php?rid=5562025&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F658%3Frss%3D1 The lake sturgeon, Acipenser fulvescens, belongs to one of the few extant nonteleost ray-finned fishes and diverged from the main vertebrate lineage about 250 million years ago. The aim of this study was to use this species to explore the peripheral neural coding strategies for sound direction and compare these results to modern bony fishes (teleosts). Extracellular recordings were made from afferent neurons innervating the saccule and lagena of the inner ear while the fish was stimulated using a shaker system. Afferents were highly directional and strongly phase locked to the stimulus. Directional response profiles resembled cosine functions, and directional preferences occurred at a wide range of stimulus intensities (spanning at least 60 dB re 1 nm displacement). Seventy-six percent of ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562025 Wed, 04 Jan 2012 05:00:00 +0100 5562025 http://www.medworm.com/index.php?rid=5562024&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F649%3Frss%3D1 Dysfunction at glutamatergic synapses has been proposed as a mechanism in the development of neuropathic pain. Here we sought to determine whether peripheral nerve injury-induced neuropathic pain results in functional changes to primary afferent synapses. Signs of neuropathic pain as well as an induction of glial fibrillary acidic protein in immunostained spinal cord sections 4 days after partial ligation of the sciatic nerve indicated the induction of neuropathic pain. We found that following nerve injury, no discernable change to kinetics of dl-α-amino-3-hydroxy-5-methylisoxazole-propionic acid (AMPA) or N-methyl-d-aspartate receptor (NMDAR)-mediated evoked excitatory postsynaptic currents (eEPSCs) could be observed in dorsal horn (lamina I/II) neurons compared with those of na&ium... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562024 Wed, 04 Jan 2012 05:00:00 +0100 5562024 http://www.medworm.com/index.php?rid=5562023&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F640%3Frss%3D1 The midbrain is an important processing area for sensory information in vertebrates. The optic tectum and its mammalian counterpart, the superior colliculus, receive multimodal, topographic information and contain a sensory map that plays a role in spatial attention and orientation movements. Many studies have investigated the tectal circuitry by cytochemistry and by characterization of particular cell types. However, only a few studies have investigated network activation throughout the depth of the tectum. Our study provides the first data on spatiotemporal activity profiles in the depth and width of the avian optic tectum. We used an optical imaging approach with voltage-sensitive dyes to investigate population responses at a high temporal and spatial resolution. With the necessary caut... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562023 Wed, 04 Jan 2012 05:00:00 +0100 5562023 http://www.medworm.com/index.php?rid=5562022&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F628%3Frss%3D1 How is working memory for different visual categories supported in the brain? Do the same principles of cortical specialization that govern the initial processing and encoding of visual stimuli also apply to their short-term maintenance? We investigated these questions with a delayed discrimination paradigm for faces, bodies, flowers, and scenes and applied both univariate and multivariate analyses to functional magnetic resonance imaging (fMRI) data. Activity during encoding followed the well-known specialization in posterior areas. During the delay interval, activity shifted to frontal and parietal regions but was not specialized for category. Conversely, activity in visual areas returned to baseline during that interval but showed some evidence of category specialization on multivariate... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562022 Wed, 04 Jan 2012 05:00:00 +0100 5562022 http://www.medworm.com/index.php?rid=5562021&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F618%3Frss%3D1 Timing is central to many coordinated actions, and the temporal accuracy of central nervous system commands presents an important limit to skilled performance. Using target-oriented throwing in a virtual environment as an example task, this study presents a novel analysis that quantifies contributions of timing accuracy and shaping of hand trajectories to performance. Task analysis reveals that the result of a throw is fully determined by the projectile position and velocity at release; zero error can be achieved by a manifold of position and velocity combinations (solution manifold). Four predictions were tested. 1) Performers learn to release the projectile closer to the optimal moment for a given arm trajectory, achieving timing accuracy levels similar to those reported in other timing ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562021 Wed, 04 Jan 2012 05:00:00 +0100 5562021 http://www.medworm.com/index.php?rid=5562020&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F603%3Frss%3D1 Ventrolateral respiratory column (VRC) circuits that modulate breathing in response to changes in central chemoreceptor drive are incompletely understood. We employed multielectrode arrays and spike train correlation methods to test predictions of the hypothesis that pre-Bötzinger complex (pre-BötC) and retrotrapezoid nucleus/parafacial (RTN-pF) circuits cooperate in chemoreceptor-evoked tuning of ventral respiratory group (VRG) inspiratory neurons. Central chemoreceptors were selectively stimulated by injections of CO2-saturated saline into the vertebral artery in seven decerebrate, vagotomized, neuromuscularly blocked, and artificially ventilated cats. Among sampled neurons in the Bötzinger complex (BötC)-to-VRG region, 70% (161 of 231) had a significant change in fir... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562020 Wed, 04 Jan 2012 05:00:00 +0100 5562020 http://www.medworm.com/index.php?rid=5562019&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F591%3Frss%3D1 Our previous study has shown that chronic heart failure (CHF) reduces expression and activation of voltage-gated sodium (Nav) channels in baroreceptor neurons, which are involved in the blunted baroreceptor neuron excitability and contribute to the impairment of baroreflex in the CHF state. The present study examined the role of mitochondria-derived superoxide in the reduced Nav channel function in coronary artery ligation-induced CHF rats. CHF decreased the protein expression and activity of mitochondrial complex enzymes and manganese SOD (MnSOD) and elevated the mitochondria-derived superoxide level in the nodose neurons compared with those in sham nodose neurons. Adenoviral MnSOD (Ad.MnSOD) gene transfection (50 multiplicity of infection) into the nodose neurons normalized the MnSOD exp... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562019 Wed, 04 Jan 2012 05:00:00 +0100 5562019 http://www.medworm.com/index.php?rid=5562018&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F573%3Frss%3D1 The object of this study was to model the relationship between neck electromyography (EMG) and three-dimensional (3-D) head kinematics during gaze behavior. In two monkeys, we recorded 3-D gaze, head orientation, and bilateral EMG activity in the sternocleidomastoid, splenius capitis, complexus, biventer cervicis, rectus capitis posterior major, and occipital capitis inferior muscles. Head-unrestrained animals fixated and made gaze saccades between targets within a 60° x 60° grid. We performed a stepwise regression in which polynomial model terms were retained/rejected based on their tendency to increase/decrease a cross-validation-based measure of model generalizability. This revealed several results that could not have been predicted from knowledge of musculoskeletal anatomy. Dur... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562018 Wed, 04 Jan 2012 05:00:00 +0100 5562018 http://www.medworm.com/index.php?rid=5562017&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F564%3Frss%3D1 A powerful early inhibition is seen in triceps surae after transcutaneous electrical stimulation of the Achilles tendon [tendon electrical stimulation (TES)]. The aim of the present study was to confirm results from surface electromyogram (SEMG) recordings that the inhibition is not wholly or partly due to stimulation of cutaneous afferents that may lie within range of the tendon electrodes. Because of methodological limitations, SEMG does not reliably identify the time course of inhibitory and excitatory reflex components. This issue was revisited here with an analysis of changes in single motor unit (SMU) firing rate [peristimulus frequencygram (PSF)] and probability [peristimulus time histogram (PSTH)] to reexamine the time course of inhibitory SMU events that follow purely cutaneous (s... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562017 Wed, 04 Jan 2012 05:00:00 +0100 5562017 http://www.medworm.com/index.php?rid=5562016&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F551%3Frss%3D1 Rats generate stereotyped exploratory (5–12 Hz) vibrissa movements when navigating through their environment. Like other rhythmic behaviors, the production of whisking relies on a subcortical pattern generator. However, the relatively large vibrissae representation in motor cortex (vMCx) suggests that cortex also contributes to the control of whisker movements. The goal of this study was to examine the relationship between neuronal activity in vMCx and the kinematics of vibrissae movements. We recorded multiunit activity (MUA) and single units in the rhythmic region of vMCx while measuring vibrissa position in awake, head-restrained rats. The rats were engaged in one of two behavioral tasks where they were rewarded for either 1) producing noncontact whisking epochs that met specified... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562016 Wed, 04 Jan 2012 05:00:00 +0100 5562016 http://www.medworm.com/index.php?rid=5562015&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F544%3Frss%3D1 This study systematically measured the haptic precision of humans exploring a virtual curved object contour with one or both hands to understand if the brain integrates haptic information from the two hemispheres. Bayesian perception theory predicts that redundant information from both hands should improve haptic estimates. Thus exploring an object with two hands should yield haptic precision that is superior to unimanual exploration. A bimanual robotic manipulandum passively moved the hands of 20 blindfolded, right-handed adult participants along virtual curved contours. Subjects indicated which contour was more "curved" (forced choice) between two stimuli of different curvature. Contours were explored uni- or bimanually at two orientations (toward or away from the body midline). Respecti... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562015 Wed, 04 Jan 2012 05:00:00 +0100 5562015 http://www.medworm.com/index.php?rid=5562014&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F532%3Frss%3D1 In humans, propriospinal neurons located at midcervical levels receive peripheral and corticospinal inputs and probably participate in the control of grip tasks, but their role in reaching movements, as observed in cats and primates, is still an open question. The effect of ulnar nerve stimulation on flexor carpi radialis (FCR) motor evoked potential (MEP) was tested during reaching tasks and tonic wrist flexion. Significant MEP facilitation was observed at the end of reach during reach-to-grasp but not during grasp, reach-to-point, or tonic contractions. MEP facilitation occurred at a longer interstimulus interval than expected for convergence of corticospinal and afferent volleys at motoneuron level and was not paralleled by a change in the H-reflex. These findings suggest convergence of... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562014 Wed, 04 Jan 2012 05:00:00 +0100 5562014 http://www.medworm.com/index.php?rid=5562013&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F2%2F517%3Frss%3D1 The existence and role of fine-temporal structure in the spiking activity of central neurons is the subject of an enduring debate among physiologists. To a large extent, the problem is a statistical one: what inferences can be drawn from neurons monitored in the absence of full control over their presynaptic environments? In principle, properly crafted resampling methods can still produce statistically correct hypothesis tests. We focus on the approach to resampling known as jitter. We review a wide range of jitter techniques, illustrated by both simulation experiments and selected analyses of spike data from motor cortical neurons. We rely on an intuitive and rigorous statistical framework known as conditional modeling to reveal otherwise hidden assumptions and to support precise conclusi... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5562013 Wed, 04 Jan 2012 05:00:00 +0100 5562013 http://www.medworm.com/index.php?rid=5539342&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F500%3Frss%3D1 As wild-type and genetically modified mice are progressively becoming the predominant models for studying locomotor physiology, the technical ability to record sensory and motor components from adult mice, in vivo, are expected to contribute to a better understanding of sensorimotor spinal cord networks. Here, specific technical and surgical details are presented on how to produce an adult decerebrate mouse preparation that can reliably produce sustained bouts of stepping, in vivo, in the absence of anesthetic drugs. Data are presented demonstrating the ability of this preparation to produce stepping during treadmill locomotion, adaptability in its responses to changes in the treadmill speed, and left-right alternation. Furthermore, intracellular recordings from motoneurons and interneuron... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539342 Fri, 23 Dec 2011 05:00:00 +0100 5539342 http://www.medworm.com/index.php?rid=5539341&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F493%3Frss%3D1 Output from the primary motor cortex contains oscillations that can have frequency-specific effects on the firing of motoneurons (MNs). Whereas much is known about the effects of oscillatory cortical drive on the output of spinal MN pools, considerably less is known about the effects on cranial motor nuclei, which govern speech/oromotor control. Here, we investigated cortical input to one such motor pool, the hypoglossal motor nucleus (HMN), which controls muscles of the tongue. We recorded intramuscular genioglossus electromyogram (EMG) and scalp EEG from healthy adult subjects performing a tongue protrusion task. Cortical entrainment of HMN population activity was assessed by measuring coherence between EEG and multiunit EMG activity. In addition, cortical entrainment of individual MN fi... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539341 Fri, 23 Dec 2011 05:00:00 +0100 5539341 http://www.medworm.com/index.php?rid=5539340&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F484%3Frss%3D1 Riluzole is the only FDA-approved drug to treat amyotrophic lateral sclerosis, but its long-term effects on motoneurons are unknown. Therefore, we treated primary mouse spinal cord cultures with 2 μM riluzole for 4–9 days and then used whole cell patch clamp to record the passive and active properties of both wild-type and SOD1G93A motoneurons. At this concentration, riluzole blocks >50% of the sodium component of a persistent inward current that plays a major role in determining motoneuron excitability. Prolonged riluzole treatment significantly decreased the amplitude of the persistent inward current. This effect was specific for SOD1G93A motoneurons, where the amplitude decreased by 55.4%. In addition, prolonged treatment hyperpolarized the resting membrane potential as well... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539340 Fri, 23 Dec 2011 05:00:00 +0100 5539340 http://www.medworm.com/index.php?rid=5539339&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F473%3Frss%3D1 Serotonergic neurons in the raphe nuclei constitute one of the most prominent neuromodulatory systems in the brain. Projections from the dorsal and median raphe nuclei provide dense serotonergic innervation of the glomeruli of olfactory bulb. Odor information is initially processed by glomeruli, thus serotonergic modulation of glomerular circuits impacts all subsequent odor coding in the olfactory system. The present study discloses that serotonin (5-HT) produces excitatory modulation of external tufted (ET) cells, a pivotal neuron in the operation of glomerular circuits. The modulation is due to a transient receptor potential (TRP) channel-mediated inward current induced by activation of 5-HT2A receptors. This current produces membrane depolarization and increased bursting frequency in ET... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539339 Fri, 23 Dec 2011 05:00:00 +0100 5539339 http://www.medworm.com/index.php?rid=5539338&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F455%3Frss%3D1 In this study we examined the activity of one of the major sources of afferent input to the motor cortex, the ventrolateral thalamus (VL). Experiments were conducted in chronically implanted cats with an extracellular single-neuron recording technique. VL neurons projecting to the motor cortex were identified by antidromic responses. During locomotion, the activity of 92% of neurons was modulated in the rhythm of strides; 67% of cells discharged one activity burst per stride, a pattern typical for the motor cortex. The characteristics of these discharges in most VL neurons appeared to be well suited to contribute to the locomotion-related activity of the motor cortex. In addition to simple locomotion, we examined VL activity during walking on a horizontal ladder, a task that requires visio... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539338 Fri, 23 Dec 2011 05:00:00 +0100 5539338 http://www.medworm.com/index.php?rid=5539337&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F448%3Frss%3D1 Long-term synaptic depression (LTD) of cerebellar parallel fiber-Purkinje cell synapses is a form of use-dependent synaptic plasticity that may be studied in cell culture. One form of LTD is induced postsynaptically through an mGlu1/Ca influx/protein kinase Cα (PKCα) cascade, and its initial expression requires phosphorylation of ser-880 in the COOH-terminal PDZ-ligand region of GluA2 and consequent binding of PICK1. This triggers postsynaptic clathrin/dynamin-mediated endocytosis of GluA2-containing surface AMPA receptors. Cerebellar LTD also has a late phase beginning 45–60 min after induction that is blocked by transcription or translation inhibitors. Here, I have sought to determine the expression mechanism of this late phase of LTD by applying various drugs and pepti... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539337 Fri, 23 Dec 2011 05:00:00 +0100 5539337 http://www.medworm.com/index.php?rid=5539336&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F442%3Frss%3D1 Interactions between auditory and somatosensory information are relevant to the neural processing of speech since speech processes and certainly speech production involves both auditory information and inputs that arise from the muscles and tissues of the vocal tract. We previously demonstrated that somatosensory inputs associated with facial skin deformation alter the perceptual processing of speech sounds. We show here that the reverse is also true, that speech sounds alter the perception of facial somatosensory inputs. As a somatosensory task, we used a robotic device to create patterns of facial skin deformation that would normally accompany speech production. We found that the perception of the facial skin deformation was altered by speech sounds in a manner that reflects the way in w... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539336 Fri, 23 Dec 2011 05:00:00 +0100 5539336 http://www.medworm.com/index.php?rid=5539335&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F433%3Frss%3D1 Humans can learn to manipulate objects with complex dynamics, including nonrigid objects with internal degrees of freedom. The first aim of this study was to assess the contribution of haptic feedback when learning to manipulate a nonrigid object. The second aim was to evaluate how learning without haptic feedback influences subsequent learning with haptic feedback and vice versa. The task involved moving a simulated mass—attached to a grasped handle via a simulated, damped spring—to a target as quickly as possible. In the haptic plus vision (HV) condition, appropriate forces were applied to the handle, which was attached to a robot. In the vision only (V) condition, these forces were turned off. Participants completed 80 trials in each condition, with one-half starting with th... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539335 Fri, 23 Dec 2011 05:00:00 +0100 5539335 http://www.medworm.com/index.php?rid=5539334&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F424%3Frss%3D1 The basal ganglia is thought to be critical for motor control and learning in mammals. In specific basal ganglia regions, gamma frequency oscillations occur during various behavioral states, including sleeping periods. Given the critical role of sleep in regulating vocal plasticity of songbirds, we examined the presence of such oscillations in the basal ganglia. In the song system nucleus Area X, epochs of high-gamma frequency (80–160 Hz) oscillation of local field potential during sleep were associated with phasic increases of neural activity. While birds were awake, activity of the same neurons increased specifically when birds were singing. Furthermore, during sleep there was a clear tendency for phase locking of spikes to these oscillations. Such patterned activity in the sleepin... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539334 Fri, 23 Dec 2011 05:00:00 +0100 5539334 http://www.medworm.com/index.php?rid=5539333&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F417%3Frss%3D1 Putative mechanisms of induction and maintenance of seizure-like activity (SLA) in the low Mg2+ model of seizures are: facilitation of NMDA receptors and decreased surface charge screening near voltage-gated channels. We have estimated the role of such screening in the early stages of SLA development at both physiological and room temperatures. External Ca2+ and Mg2+ promote a depolarization shift of the sodium channel voltage sensitivity; when examined in hippocampal pyramidal neurons, the effect of Ca2+ was 1.4 times stronger than of Mg2+. Removing Mg2+ from the extracellular solution containing 2 mM Ca2+ induced recurrent SLA in hippocampal CA1 pyramidal layer in 67% of slices. Reduction of [Ca2+]o to 1 mM resulted in 100% appearance of recurrent SLA or continuous SLA. Both delay before... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539333 Fri, 23 Dec 2011 05:00:00 +0100 5539333 http://www.medworm.com/index.php?rid=5539332&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F407%3Frss%3D1 Serotonin (5-hydroxytryptamine, 5-HT) inhibits the induction of long-term synaptic plasticity in layer 2/3 of the visual cortex at the end of its critical period in rats. However, the cellular and molecular mechanisms remain unclear. Since inhibitory influence is crucial in the induction of synaptic plasticity, the effect of 5-HT on inhibitory transmission was investigated in layer 2/3 pyramidal neurons of the primary visual cortex. The amplitude of inhibitory postsynaptic current (IPSC), but not excitatory postsynaptic current, evoked by stimulation of the underlying layer 4, was increased by ~20% with a bath application of 5-HT. The amplitude of miniature IPSC was also increased by the application of 5-HT, while the paired-pulse ratio was not changed. The facilitating effect of 5-HT on I... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539332 Fri, 23 Dec 2011 05:00:00 +0100 5539332 http://www.medworm.com/index.php?rid=5539331&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F393%3Frss%3D1 Absence seizures consist of a brief and sudden impairment of consciousness. They are characterized by bilaterally synchronized spike and wave discharges (SWDs), which reflect abnormal oscillations in the thalamocortical loops. Recent studies have suggested that the basal ganglia are involved in generation of the SWDs, but their roles are poorly understood at the molecular and cellular levels. Here we studied the pathophysiological roles of the basal ganglia, using in vivo and in vitro measurements of tottering mice, a well-established model of absence epilepsy. We found that the membrane excitability in subthalamic nucleus (STN) neurons was enhanced in tottering mice, which resulted from reduced hyperpolarization-activated cyclic nucleotide-gated (HCN) channel activity. Pharmacological blo... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539331 Fri, 23 Dec 2011 05:00:00 +0100 5539331 http://www.medworm.com/index.php?rid=5539330&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F384%3Frss%3D1 Much research has focused on how people stop initiated response tendencies when instructed by a signal. Stopping of this kind appears to have global effects on the motor system. For example, by delivering transcranial magnetic stimulation (TMS) over the leg area of the primary motor cortex, it is possible to detect suppression in the leg when the hand is being stopped (Badry R et al. Suppression of human cortico-motoneuronal excitability during the stop-signal task. Clin Neurophysiol 120: 1717–1723, 2009). Here, we asked if such "global suppression" can be observed proactively, i.e., when people anticipate they might have to stop. We used a conditional stop signal task, which allows the measurement of both an "anticipation phase" (i.e., where proactive control is applied) and a "stop... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539330 Fri, 23 Dec 2011 05:00:00 +0100 5539330 http://www.medworm.com/index.php?rid=5539329&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F364%3Frss%3D1 Deep brain stimulation (DBS) provides dramatic tremor relief when delivered at high-stimulation frequencies (more than ~100 Hz), but its mechanisms of action are not well-understood. Previous studies indicate that high-frequency stimulation is less effective when the stimulation train is temporally irregular. The purpose of this study was to determine the specific characteristics of temporally irregular stimulus trains that reduce their effectiveness: long pauses, bursts, or irregularity per se. We isolated these characteristics in stimulus trains and conducted intraoperative measurements of postural tremor in eight volunteers. Tremor varied significantly across stimulus conditions (P < 0.015), and stimulus trains with pauses were significantly less effective than stimulus trains withou... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539329 Fri, 23 Dec 2011 05:00:00 +0100 5539329 http://www.medworm.com/index.php?rid=5539328&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F357%3Frss%3D1 Native cowhage spicules, and heat-inactivated spicules containing histamine or capsaicin, evoke similar sensations of itch and nociceptive sensations in humans. In ongoing studies of the peripheral neural mechanisms of chemical itch and pain in the mouse, extracellular electrophysiological recordings were obtained, in vivo, from the cell bodies of mechanosensitive nociceptive neurons in response to spicule stimuli delivered to their cutaneous receptive fields (RFs) on the distal hindlimb. A total of 43 mechanosensitive, cutaneous, nociceptive neurons with axonal conduction velocities in the C-fiber range (C-nociceptors) were classified as CM if responsive to noxious mechanical stimuli, such as pinch, or CMH if responsive to noxious mechanical and heat stimuli (51°C, 5 s). The tips of n... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539328 Fri, 23 Dec 2011 05:00:00 +0100 5539328 http://www.medworm.com/index.php?rid=5539327&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F346%3Frss%3D1 Successful behavior demands motor learning to be transferable in some cases (e.g., adjusting walking patterns as we develop and age) and context specific in others (e.g., learning to walk in high heels). Here we investigated differences in motor learning transfer in people learning a new walking pattern on a split-belt treadmill, where the legs move at different speeds. We hypothesized that transfer of the newly acquired walking pattern on the treadmill to natural over ground walking might depend on the pattern of errors experienced during learning. Error patterns within a person's natural range might be experienced as endogenous (i.e., produced by the body), encouraging general adjustments that transfer across contexts. On the other hand, larger errors might be experienced as exogenous (i... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539327 Fri, 23 Dec 2011 05:00:00 +0100 5539327 http://www.medworm.com/index.php?rid=5539326&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F336%3Frss%3D1 In conclusion, our findings suggest the presence of in-parallel NMCs within the superficial muscles of the GHJ and show that biomechanical parameters, such as the MA at end-point movement position, influence the function of each NMC and its contribution to alternating patterns of agonist and antagonist muscle activity typical of ballistic movement. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539326 Fri, 23 Dec 2011 05:00:00 +0100 5539326 http://www.medworm.com/index.php?rid=5539325&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F315%3Frss%3D1 Our previous work showed that nerve growth factor (NGF) increased the excitability of small-diameter capsaicin-sensitive sensory neurons by activating the p75 neurotrophin receptor and releasing sphingolipid-derived second messengers. Whole cell patch-clamp recordings were used to establish the signaling pathways whereby NGF augments action potential (AP) firing (i.e., sensitization). Inhibition of MEK1/2 (PD-98059), PLC (U-73122, neomycin), or conventional/novel isoforms of PKC (bisindolylmaleimide I) had no effect on the sensitization produced by NGF. Pretreatment with a membrane-permeable, myristoylated pseudosubstrate inhibitor of atypical PKCs (aPKCs: PKM, PKC, and PKC/) blocked the NGF-induced increase in AP firing. Inhibitors of phosphatidylinositol 3-kinase (PI3K) also blocked the ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539325 Fri, 23 Dec 2011 05:00:00 +0100 5539325 http://www.medworm.com/index.php?rid=5539324&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F306%3Frss%3D1 The purpose of the current study was to investigate corticospinal contributions to locomotor drive to leg muscles involved in cycling. We studied 1) if activation of inhibitory interneurons in the cortex via subthreshold transcranial magnetic stimulation (TMS) caused a suppression of EMG and 2) how the responses to stimulation of the motor cortex via TMS and cervicomedullary stimulation (CMS) were modulated across the locomotor cycle. TMS at intensities subthreshold for activation of the corticospinal tract elicited suppression of EMG for approximately one-half of the subjects and muscles during cycling, and in matched static contractions in vastus lateralis. There was also significant modulation in the size of motor-evoked potentials (MEPs) elicited by TMS across the locomotor cycle (P &l... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539324 Fri, 23 Dec 2011 05:00:00 +0100 5539324 http://www.medworm.com/index.php?rid=5539323&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F292%3Frss%3D1 Expression of the 5-HT1Apl(a) receptor in Aplysia pleural sensory neurons inhibited 5-HT-mediated translocation of the novel PKC Apl II in sensory neurons and prevented PKC-dependent synaptic facilitation at sensory to motoneuron synapses (Nagakura et al. 2010). We now demonstrate that the ability of inhibitory receptors to block PKC activation is a general feature of inhibitory receptors and is found after expression of the 5-HT1Apl(b) receptor and with activation of endogenous dopamine and FMRFamide receptors in sensory neurons. Pleural sensory neurons are heterogeneous for their inhibitory response to endogenous transmitters, with dopamine being the most prevalent, followed by FMRFamide, and only a small number of neurons with inhibitory responses to 5-HT. The inhibitory response is dom... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539323 Fri, 23 Dec 2011 05:00:00 +0100 5539323 http://www.medworm.com/index.php?rid=5539322&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F283%3Frss%3D1 ACh modulates neuronal activity throughout the cerebral cortex, including the primary visual cortex (V1). However, a number of issues regarding this modulation remain unknown, such as the effect and its function and the receptor subtypes involved. To address these issues, we combined extracellular single-unit recordings and microiontophoretic administration of ACh and measured V1 neuronal responses to drifting sinusoidal grating stimuli in anesthetized macaque monkeys. ACh was found to have mostly facilitatory effects on the visual responses, although some cases of suppressive effects were also seen. To assess the functional role of ACh, we further examined how ACh modulates the stimulus contrast-response function, finding that the response gain increased with the facilitatory effect. The ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539322 Fri, 23 Dec 2011 05:00:00 +0100 5539322 http://www.medworm.com/index.php?rid=5539321&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F273%3Frss%3D1 The inferior olive (IO) is a major component of the eyeblink conditioning neural network. The cerebellar learning hypothesis assumes that the IO supplies the cerebellum with a "teaching" unconditioned stimulus input required for the acquisition of the conditioned response (CR) and predicts that inactivating this input leads to the extinction of CRs. Previous tests of this prediction attempted to block the teaching input by blocking glutamatergic sensory inputs in the IO. These tests were inconclusive because blocking glutamate neurotransmission in the IO produces a nonspecific tonic malfunction of cerebellar circuits. The purpose of the present experiment was to examine whether the behavioral outcomes of blocking glutamate receptors in the IO could be counterbalanced by reducing GABA-media... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539321 Fri, 23 Dec 2011 05:00:00 +0100 5539321 http://www.medworm.com/index.php?rid=5539320&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F265%3Frss%3D1 Hindlimb motoneuron excitability was compared among exercise-trained (E), sedentary (S), and spinal cord transected (T) Sprague-Dawley rats by examining the slope of the frequency-current (F/I) relationship with standard intracellular recording techniques in rats anesthetized with ketamine-xylazine. The T group included spinal transected and spinal isolated rats; the E animals were either spontaneously active (exercise wheel) or treadmill trained; and rats in the S group were housed in pairs. An analysis of motoneuron initial [1st interspike interval (ISI)], early (mean of 1st three ISIs), and steady-state (mean of last 3 ISIs) discharge rate slopes resulting from increasing and decreasing 500-ms injected square-wave depolarizing current pulses was used to describe rhythmic motoneuron prop... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539320 Fri, 23 Dec 2011 05:00:00 +0100 5539320 http://www.medworm.com/index.php?rid=5539319&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F257%3Frss%3D1 Neuronal nicotinic acetylcholine receptors (nAChRs) are expressed on hypoglossal motor neurons (XII MNs) that innervate muscles of the tongue. Activation of XII MN nAChRs evokes depolarizing currents, which are important for regulating the size and stiffness of the upper airway. Although data show that chronic developmental nicotine exposure (DNE) blunts cholinergic neurotransmission in the XII motor nucleus, it is unclear how nAChRs are involved. Therefore, XII MN nAChR desensitization and recovery were examined in tissues from DNE or control pups using a medullary slice preparation and tight-seal whole cell patch-clamp recordings. nAChR-mediated inward currents were evoked by brief pressure pulses of nicotine or the α4β2 nAChR agonist RJR-2403. We found that, regardless of tre... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539319 Fri, 23 Dec 2011 05:00:00 +0100 5539319 http://www.medworm.com/index.php?rid=5539318&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F250%3Frss%3D1 We examined the efficacy of using chronic passive muscle stretching to augment RI. The influence of 3 wk of plantarflexor stretching (4 x 30 s, two times/day) on RI of soleus and gastrocnemius initiated by tonic, voluntary dorsiflexion contractions [20% of maximum voluntary contraction (MVC)] was examined in 11 healthy men who performed stretch training and in nine nontraining controls. Hoffmann's reflexes (H-reflexes) were elicited by tibial nerve stimulation during both weak isometric (2% MVC) plantarflexions and dorsiflexion contractions at 20% MVC. Changes were examined at three joint angles, normalized to each subject's range of motion (ROM; plantarflexed = 10 ± 0°, neutral = –3.3 ± 2.9°, dorsiflexed = –16.5 ± 5.6°). No changes were detecte... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539318 Fri, 23 Dec 2011 05:00:00 +0100 5539318 http://www.medworm.com/index.php?rid=5539317&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F239%3Frss%3D1 In many animals, the effects of sensory feedback on motor output change during locomotion. These changes can occur as reflex reversals in which sense organs that activate muscles to counter perturbations in posture control instead reinforce movements in walking. The mechanisms underlying these changes are only partially understood. As such, it is unclear whether reflex reversals are modulated when locomotion is adapted, such as during changes in walking direction or in turning movements. We investigated these questions in the stick insect Carausius morosus, where sensory signals from the femoral chordotonal organ are known to produce resistance reflexes at rest but assistive movements during walking. We studied how intersegmental signals from neighboring legs affect the generation of refle... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539317 Fri, 23 Dec 2011 05:00:00 +0100 5539317 http://www.medworm.com/index.php?rid=5539316&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F226%3Frss%3D1 We present evidence that plasticity in at least two brain regions can mediate extinction of responses produced by trace eyelid conditioning, where the CS and the reinforcing stimulus are separated by a stimulus-free interval. We observed individual differences in the effects of blocking extinction mechanisms in the cerebellum, the structure that, along with several forebrain structures, mediates acquisition of trace eyelid responses; in some rabbits extinction was prevented, whereas in others it was largely unaffected. We also show that cerebellar mechanisms can mediate extinction when noncerebellar mechanisms are bypassed. Together, these observations indicate that trace eyelid responses can be extinguished via processes operating at more than one site, one in the cerebellum and one upstr... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539316 Fri, 23 Dec 2011 05:00:00 +0100 5539316 http://www.medworm.com/index.php?rid=5539315&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F216%3Frss%3D1 Sway is reduced by light nonsupporting touch between parts of the body and a fixed surface. This effect is assumed to reflect augmentation of sensory cues for sway by point-of-contact reaction forces. It has been shown that movement of the contact surface can increase sway relative to an earth-fixed contact. Light touch contact with another person, for example, holding hands, affords a moving contact due to partner sway. We asked whether interpersonal light touch (IPLT) would increase sway relative to standing alone. We expected effects on sway to vary as a function of the site of contact and the postural stability of each partner. Eight pairs of participants, standing in either normal bipedal or tandem Romberg stance with eyes closed and using IPLT (finger to finger or shoulder to shoulde... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539315 Fri, 23 Dec 2011 05:00:00 +0100 5539315 http://www.medworm.com/index.php?rid=5539314&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F205%3Frss%3D1 The induction of long-term potentiation (LTP) and long-term depression (LTD) of excitatory postsynaptic currents was investigated in proximal synapses of layer 2/3 pyramidal cells of the rat medial prefrontal cortex. The spike timing-dependent plasticity (STDP) induction protocol of negative timing, with postsynaptic leading presynaptic stimulation of action potentials (APs), induced LTD as expected from the classical STDP rule. However, the positive STDP protocol of presynaptic leading postsynaptic stimulation of APs predominantly induced a presynaptically expressed LTD rather than the expected postsynaptically expressed LTP. Thus the induction of plasticity in layer 2/3 pyramidal cells does not obey the classical STDP rule for positive timing. This unusual STDP switched to a classical ti... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539314 Fri, 23 Dec 2011 05:00:00 +0100 5539314 http://www.medworm.com/index.php?rid=5539313&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F196%3Frss%3D1 GABAA receptors mediate mainly inhibitory effects, but there are also many examples of excitatory effects in both mammalian and invertebrate preparations. Here, we aimed to create a complete, quantitative picture of GABAA-mediated excitation in a mechanosensory neuron where this phenomenon has been well established. We used muscimol to activate GABAA receptors in spider VS-3 neurons and measured the dynamic behavior independently and separately at each of three stages of mechanoreception (receptor current, receptor potential, and action potentials) before and during modulation. We calculated frequency response functions between each stage, estimated information as signal entropy, and estimated information capacity from coherence. Since coherence is sensitive to both noise and nonlinearity,... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539313 Fri, 23 Dec 2011 05:00:00 +0100 5539313 http://www.medworm.com/index.php?rid=5539312&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F178%3Frss%3D1 For the past five decades there has been wide acceptance of a relationship between the firing rate of motor units and the afterhyperpolarization of motoneurons. It has been promulgated that the higher-threshold, larger-soma, motoneurons fire faster than the lower-threshold, smaller-soma, motor units. This relationship was based on studies on anesthetized cats with electrically stimulated motoneurons. We questioned its applicability to motor unit control during voluntary contractions in humans. We found that during linearly force-increasing contractions, firing rates increased as exponential functions. At any time and force level, including at recruitment, the firing rate values were inversely related to the recruitment threshold of the motor unit. The time constants of the exponential func... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539312 Fri, 23 Dec 2011 05:00:00 +0100 5539312 http://www.medworm.com/index.php?rid=5539311&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F159%3Frss%3D1 Recent evidence suggests that complex spatiotemporal patterns of muscle activity can be explained with a low-dimensional set of muscle synergies or M-modes. While it is clear that both spatial and temporal aspects of muscle coordination may be low dimensional, constraints on spatial versus temporal features of muscle coordination likely involve different neural control mechanisms. We hypothesized that the low-dimensional spatial and temporal features of muscle coordination are independent of each other. We further hypothesized that in reactive feedback tasks, spatially fixed muscle coordination patterns—or muscle synergies—are hierarchically recruited via time-varying neural commands based on delayed task-level feedback. We explicitly compared the ability of spatially fixed (SF... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539311 Fri, 23 Dec 2011 05:00:00 +0100 5539311 http://www.medworm.com/index.php?rid=5539310&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F148%3Frss%3D1 We report presently that knockout of acd-1 in glia exacerbates sensory deficits caused by another mutant: the hypomorphic allele of the cGMP-gated channel subunit tax-2. Furthermore, sensory deficits caused by mutations in Gi protein odr-3 and guanylate cyclase daf-11, which regulate the activity of TAX-2/TAX-4 channels, are worsened by knockout of acd-1. We also show that sensory neurons of acd-1 tax-2(p694) double mutants fail to undergo changes in intracellular Ca2+ when animals are exposed to low concentrations of attractant. Finally, we show that exogenous expression of TRPV1 in sensory neurons and exposure to capsaicin rescue sensory deficits of acd-1 tax-2(p694) mutants, suggesting that sensory deficits of these mutants are bypassed by increasing neuronal excitability. Our data sugg... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539310 Fri, 23 Dec 2011 05:00:00 +0100 5539310 http://www.medworm.com/index.php?rid=5539309&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F134%3Frss%3D1 Studies with patients and functional magnetic resonance imaging investigations have demonstrated that the cerebellum plays an essential role in adaptation to visuomotor rotation and force field perturbation. To identify cerebellar structures involved in the two tasks, we studied 19 patients with focal lesions after cerebellar infarction. Focal lesions were manually traced on magnetic resonance images and normalized using a new spatially unbiased template of the cerebellum. In addition, we reanalyzed data from 14 patients with cerebellar degeneration using voxel-based morphometry. We found that adjacent regions with only little overlap in the anterior arm area (lobules IV to VI) are important for adaptation in both tasks. Although adaptation to the force field task lay more anteriorly (lobu... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539309 Fri, 23 Dec 2011 05:00:00 +0100 5539309 http://www.medworm.com/index.php?rid=5539308&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F126%3Frss%3D1 Efficient control of reciprocal activation and cocontraction of the muscles are critical to perform skillful actions with suitable force and impedance. However, it remains unclear how the brain controls force and impedance while recruiting the same set of muscles as actuators. Does control take place at the single muscle level leading to force and impedance, or are there higher-order centers dedicated to controlling force and impedance? We addressed this question using functional MRI during voluntary isometric wrist contractions with online electromyogram feedback. Comparison of the brain activity between the conditions requiring control of either wrist torque or cocontraction demonstrates that blood oxygen level-dependent activity in the caudo-dorsal premotor cortex (PMd) correlates well ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539308 Fri, 23 Dec 2011 05:00:00 +0100 5539308 http://www.medworm.com/index.php?rid=5539307&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F114%3Frss%3D1 Interlimb coordination of crawling kinematics in humans shares features with other primates and nonprimate quadrupeds, and it has been suggested that this is due to a similar organization of the locomotor pattern generators (CPGs). To extend the previous findings and to further explore the neural control of bipedal vs. quadrupedal locomotion, we used a crawling paradigm in which healthy adults crawled on their hands and feet at different speeds and at different surface inclinations (13°, 27°, and 35°). Ground reaction forces, limb kinematics, and electromyographic (EMG) activity from 26 upper and lower limb muscles on the right side of the body were collected. The EMG activity was mapped onto the spinal cord in approximate rostrocaudal locations of the motoneuron pools to chara... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539307 Fri, 23 Dec 2011 05:00:00 +0100 5539307 http://www.medworm.com/index.php?rid=5539306&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F103%3Frss%3D1 In this study, we examined the contribution of a low-threshold calcium current [ICa(T)] to locomotor-related activity in the neonatal mouse. Specifically, the role of ICa(T) was studied during chemically induced, locomotor-like activity in the isolated whole cord and in a genetically distinct population of ventromedial spinal interneurons marked by the homeobox gene Hb9. In isolated whole spinal cords, cycle frequency was decreased in the presence of low-threshold calcium channel blockers, which suggests a role for ICa(T) in the network that produces rhythmic, locomotor-like activity. Additionally, we used Hb9 interneurons as a model to study the cellular responses to application of low-threshold calcium channel blockers. In transverse slice preparations from transgenic Hb9::enhanced green... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539306 Fri, 23 Dec 2011 05:00:00 +0100 5539306 http://www.medworm.com/index.php?rid=5539305&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F90%3Frss%3D1 Reaching movements are subject to noise associated with planning and execution, but precisely how these noise sources interact to determine patterns of endpoint variability in three-dimensional space is not well understood. For frontal plane movements, variability is largest along the depth axis (the axis along which visual planning noise is greatest), with execution noise contributing to this variability along the movement direction. Here we tested whether these noise sources interact in a similar way for movements directed in depth. Subjects performed sequences of two movements from a single starting position to targets that were either both contained within a frontal plane ("frontal sequences") or where the first was within the frontal plane and the second was directed in depth ("depth ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539305 Fri, 23 Dec 2011 05:00:00 +0100 5539305 http://www.medworm.com/index.php?rid=5539304&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F78%3Frss%3D1 In this study, noninvasive magnetoencephalography (MEG) recordings are obtained from human subjects actively listening to spoken narratives, in both simple and cocktail party-like auditory scenes. By modeling how acoustic features of speech are encoded in ongoing MEG activity as a spectrotemporal response function, we demonstrate that the slow temporal modulations of speech in a broad spectral region are represented bilaterally in auditory cortex by a phase-locked temporal code. For speech presented monaurally to either ear, this phase-locked response is always more faithful in the right hemisphere, but with a shorter latency in the hemisphere contralateral to the stimulated ear. When different spoken narratives are presented to each ear simultaneously (dichotic listening), the resulting c... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539304 Fri, 23 Dec 2011 05:00:00 +0100 5539304 http://www.medworm.com/index.php?rid=5539303&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F65%3Frss%3D1 Hippocampal theta oscillations (3–12 Hz) may reflect a mechanism for sensorimotor integration in rats (Bland BH. Prog Neurobiol 26: 1–54, 1986); however, it is unknown whether cortical theta activity underlies sensorimotor integration in humans. Rather, the mu rhythm (8–12 Hz) is typically found to desynchronize during movement. We measured oscillatory EEG activity for two conditions of an instructed delayed reaching paradigm. Conditions 1 and 2 were designed to differentially manipulate the contribution of the ventral visuomotor stream during the response initiation phase. We tested the hypothesis that theta activity would reflect changes in the relevant sensorimotor network: condition 2 engaged ventral stream mechanisms to a greater extent than condition 1. Theta oscill... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539303 Fri, 23 Dec 2011 05:00:00 +0100 5539303 http://www.medworm.com/index.php?rid=5539302&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F50%3Frss%3D1 We have addressed the source and nature of the persistent neural activity that bridges the stimulus-free gap between the conditioned stimulus (CS) and unconditioned stimulus (US) during trace eyelid conditioning. Previous work has demonstrated that this persistent activity is necessary for trace eyelid conditioning: CS-elicited activity in mossy fiber inputs to the cerebellum does not extend into the stimulus-free trace interval, which precludes the cerebellar learning that mediates conditioned response expression. In behaving rabbits we used in vivo recordings from a region of medial prefrontal cortex (mPFC) that is necessary for trace eyelid conditioning to test the hypothesis that neurons there generate activity that persists beyond CS offset. These recordings revealed two patterns of a... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539302 Fri, 23 Dec 2011 05:00:00 +0100 5539302 http://www.medworm.com/index.php?rid=5539301&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F42%3Frss%3D1 Output from steroidogenic factor-1 (SF-1) neurons in the ventromedial nucleus of the hypothalamus (VMH) is anorexigenic. SF-1 neurons express brain-derived neurotrophic factor (BDNF) that contributes to the regulation of food intake and body weight. Here I show that regulation of GABAergic inputs onto SF-1 neurons by endogenous BDNF determines the anorexigenic outcome from the VMH. Single-cell RT-PCR analysis reveals that one-third of SF-1 neurons express BDNF and that only a subset of BDNF-expressing SF-1 neurons coexpresses the melanocortin receptor type 4. Whole cell patch-clamp analysis of SF-1 neurons in the VMH shows that exogenous BDNF significantly increases the frequency of spontaneous GABAergic inhibitory postsynaptic currents (sIPSCs). This enhancement of GABA drive readily decr... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539301 Fri, 23 Dec 2011 05:00:00 +0100 5539301 http://www.medworm.com/index.php?rid=5539300&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F29%3Frss%3D1 After unilateral peripheral vestibular lesions, the brain plasticity underlying early recovery from the static symptoms is not fully understood. Principal cells of the chick tangential nucleus offer a subset of morphologically defined vestibular nuclei neurons to study functional changes after vestibular lesions. Chickens show posture and balance deficits immediately after unilateral vestibular ganglionectomy (UVG), but by 3 days most subjects begin to recover, although some remain uncompensated. With the use of whole cell voltage-clamp, spontaneous excitatory and inhibitory postsynaptic currents (sEPSCs and sIPSCs) and miniature excitatory and inhibitory postsynaptic currents (mEPSCs and mIPSCs) were recorded from principal cells in brain slices 1 and 3 days after UVG. One day after UVG, ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539300 Fri, 23 Dec 2011 05:00:00 +0100 5539300 http://www.medworm.com/index.php?rid=5539299&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F12%3Frss%3D1 To quantify the contribution of sensory information to multisegmental frontal plane balance control in humans, we developed a feedback control model to account for experimental data. Subjects stood with feet close together on a surface that rotated according to a pseudorandom waveform at three different amplitudes. Experimental frequency-response functions and impulse-response functions were measured to characterize lower body (LB) and upper body (UB) motion evoked during surface rotations while subjects stood with eyes open or closed. The model assumed that corrective torques in LB and UB segments were generated with no time delay from intrinsic musculoskeletal mechanisms and with time delay from sensory feedback mechanisms. It was found that subjects' LB control was primarily based on se... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539299 Fri, 23 Dec 2011 05:00:00 +0100 5539299 http://www.medworm.com/index.php?rid=5539298&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F5%3Frss%3D1 The unusual membrane motor protein prestin is essential for mammalian hearing and for the survival of cochlear outer hair cells. While prestin has been demonstrated to be a homooligomer, by Western blot and FRET analyses, the stoichiometry of self association is unclear. Prestin, coupled to the enhanced green fluorescent protein, was synthesized and membrane targeted in human embryonic kidney cells by plasmid transfection. Fragments of membrane containing immobilized fluorescent molecules were isolated by osmotic lysis. Diffraction-limited fluorescent spots consistent in size with single molecules were observed. Under continuous excitation, the spots bleached to background in sequential and approximately equal-amplitude steps. The average step count to background levels was 2.7. A binomial... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539298 Fri, 23 Dec 2011 05:00:00 +0100 5539298 http://www.medworm.com/index.php?rid=5539297&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F107%2F1%2F1%3Frss%3D1 This article critically evaluates the contemporary approach of combined tDCS and neuroimaging as a means to provide novel insights in understanding the neurophysiological and neuroplastic processes modulated by this brain stimulation technique. We end by briefly suggesting further lines of inquiry. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5539297 Fri, 23 Dec 2011 05:00:00 +0100 5539297 http://www.medworm.com/index.php?rid=5488575&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3230%3Frss%3D1 In this study, we tested various cis elements to optimize transgene expression at transcriptional, posttranscriptional, and posttranslational levels and combined them together to create the high-level neuronal transgene expression cassette pUNISHER. Using a second-generation adenoviral vector system in combination with the pUNISHER cassette, we characterized its rate of onset of detectable expression and levels of expression compared with a neurospecific expression cassette driven by the 470-bp human synapsin promoter in vitro and in vivo. Our results demonstrate in primary neurons that the pUNISHER cassette, in a recombinant adenovirus type 5 background, led to a faster rate of onset of detectable transgene expression and higher level of transgene expression. More importantly, this casset... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488575 Thu, 08 Dec 2011 05:00:00 +0100 5488575 http://www.medworm.com/index.php?rid=5488574&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3216%3Frss%3D1 Across-trial averaging is a widely used approach to enhance the signal-to-noise ratio (SNR) of event-related potentials (ERPs). However, across-trial variability of ERP latency and amplitude may contain physiologically relevant information that is lost by across-trial averaging. Hence, we aimed to develop a novel method that uses 1) wavelet filtering (WF) to enhance the SNR of ERPs and 2) a multiple linear regression with a dispersion term (MLRd) that takes into account shape distortions to estimate the single-trial latency and amplitude of ERP peaks. Using simulated ERP data sets containing different levels of noise, we provide evidence that, compared with other approaches, the proposed WF+MLRd method yields the most accurate estimate of single-trial ERP features. When applied to a real l... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488574 Thu, 08 Dec 2011 05:00:00 +0100 5488574 http://www.medworm.com/index.php?rid=5488573&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3205%3Frss%3D1 Behaviors are generated from complex interactions among networks of neurons. Single-unit ensemble recording has been used to identify multiple neurons in functioning networks. These recordings have provided insight into interactions among neurons in local and distributed circuits. Recorded units in these ensembles have been classed based on waveform type, firing pattern, and physical location. To identify individual projection neurons in a cortical network, we have paired tetrode recording with antidromic stimulation. We developed techniques that enable antidromic identification of single units and study of functional interactions between these neurons and other circuit elements. These methods have been developed in the zebra finch and should be applicable, with potential modifications tha... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488573 Thu, 08 Dec 2011 05:00:00 +0100 5488573 http://www.medworm.com/index.php?rid=5488572&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3195%3Frss%3D1 Prepulse inhibition (PPI) is a widespread sensorimotor gating phenomenon characterized by a decrease in startle magnitude if a nonstartling stimulus is presented 20–1,000 ms before a startling stimulus. Dopaminergic agonists disrupt behavioral PPI in various animal models. This provides an important neuropharmacological link to schizophrenia patients that typically show PPI deficits at distinct (60 ms) prepulse-pulse intervals. Here, we study time-dependent effects of dopaminergic modulation in the goldfish Mauthner cell (M-cell) startle network, which shows PPI-like behavioral and physiological startle attenuations. The unique experimental accessibility of the M-cell system allows investigating the underlying cellular mechanism with physiological stimuli in vivo. Our results show th... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488572 Thu, 08 Dec 2011 05:00:00 +0100 5488572 http://www.medworm.com/index.php?rid=5488571&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3185%3Frss%3D1 The mechanism by which distinct subprocesses in the brain are coordinated is a central conundrum of systems neuroscience. The parietal lobe is thought to play a key role in visual feature integration, and oscillatory activity in the gamma frequency range has been associated with perception of coherent objects and other tasks requiring neural coordination. Here, we examined the neural correlates of integrating mental representations in working memory and hypothesized that parietal gamma activity would be related to the success of cognitive coordination. Working memory is a classic example of a cognitive operation that requires the coordinated processing of different types of information and the contribution of multiple cognitive domains. Using magnetoencephalography (MEG), we report parieta... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488571 Thu, 08 Dec 2011 05:00:00 +0100 5488571 http://www.medworm.com/index.php?rid=5488570&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3173%3Frss%3D1 We have examined the question of how the level of expression of sodium channel Nav1.8 affects the function of dorsal root ganglion (DRG) neurons that also express Nav1.7 channels and, conversely, how the level of expression of sodium channel Nav1.7 affects the function of DRG neurons that also express Nav1.8, using computer simulations. Our results demonstrate several previously undescribed effects of expression of Nav1.7: 1) at potentials more negative than –50 mV, increasing Nav1.7 expression reduces current threshold. 2) Nav1.7 reduces, but does not eliminate, the dependence of action potential (AP) threshold on membrane potential. 3) In cells that express Nav1.8, the presence of Nav1.7 results in larger amplitude subthreshold oscillations and increases the frequency of repetitive... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488570 Thu, 08 Dec 2011 05:00:00 +0100 5488570 http://www.medworm.com/index.php?rid=5488569&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3157%3Frss%3D1 Studies of intermanual transfer have been used to probe representations formed during skill acquisition. We employ a new method that provides a continuous assay of intermanual transfer, intermixing right- and left-hand trials while limiting visual feedback to right-hand movements. We manipulated the degree of awareness of the visuomotor rotation, introducing a 22.5° perturbation in either an abrupt single step or gradually in ~1° increments every 10 trials. Intermanual transfer was observed with the direction of left-hand movements shifting in the opposite direction of the rotation over the course of training. The transfer on left-hand trials was less than that observed in the right hand. Moreover, the magnitude of transfer was larger in our mixed-limb design compared with the stan... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488569 Thu, 08 Dec 2011 05:00:00 +0100 5488569 http://www.medworm.com/index.php?rid=5488568&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3145%3Frss%3D1 In randomly bred rats, orally applied ethanol stimulates neural substrates for appetitive sweet taste. To study associations between ethanol's oral sensory characteristics and genetically mediated ethanol preference, we made electrophysiological recordings of oral responses (spike density) by taste-sensitive nucleus tractus solitarii neurons in anesthetized selectively bred ethanol-preferring (P) rats and their genetically heterogeneous Wistar (W) control strain. Stimuli (25 total) included ethanol [3%, 5%, 10%, 15%, 25%, and 40% (vol/vol)], a sucrose series (0.01, 0.03, 0.1, 0.3, 0.5, and 1 M), and other sweet, salt, acidic, and bitter stimuli; 50 P and 39 W neurons were sampled. k-means clustering applied to the sucrose response series identified cells showing high (S1) or relatively low... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488568 Thu, 08 Dec 2011 05:00:00 +0100 5488568 http://www.medworm.com/index.php?rid=5488567&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3136%3Frss%3D1 Experience shapes both central olfactory system function and odor perception. In piriform cortex, odor experience appears critical for synthetic processing of odor mixtures, which contributes to perceptual learning and perceptual acuity, as well as contributing to memory for events and/or rewards associated with odors. Here, we examined the effect of odor fear conditioning on piriform cortical single-unit responses to the learned aversive odor, as well as its effects on similar (overlapping mixtures) in freely moving rats. We found that odor-evoked fear responses were training paradigm dependent. Simple association of a condition stimulus positive (CS+) odor with foot shock (unconditioned stimulus) led to generalized fear (cue-evoked freezing) to similar odors. However, after differential ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488567 Thu, 08 Dec 2011 05:00:00 +0100 5488567 http://www.medworm.com/index.php?rid=5488566&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3129%3Frss%3D1 The orexins (orexin-A and orexin-B) are neuropeptides that are secreted from neurons in the lateral hypothalamus and that participate in the regulation of feeding behavior. It remains to be determined, however, how the orexins exert their effects on feeding behavior, including masticatory movements. To this end, we analyzed food intake behavior and masticatory muscle activity using video analysis and electromyography (EMG) recording methods. The results showed that the cumulative food intake over 4 h was larger in rats intraventricularly injected with either orexin-A or orexin-B than in saline-injected control rats. The latency to eating and the feeding time for a fixed amount of pellets were shortened by injections of orexins in a dose-dependent manner, with a more potent effect by orexin... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488566 Thu, 08 Dec 2011 05:00:00 +0100 5488566 http://www.medworm.com/index.php?rid=5488565&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3119%3Frss%3D1 We studied duration tuning in neurons of the inferior colliculus (IC) of the mustached bat. Duration-tuned neurons in the IC of the mustached bat fall into three main types: short (16 of 136), band (34 of 136), and long (29 of 136) pass. The remaining 51 neurons showed no selectivity for the duration of sounds. The distribution of best durations was double peaked with maxima around 3 and 17 ms, which correlate with the duration of the short frequency-modulated (FM) and the long constant-frequency (CF) signals emitted by Pteronotus parnellii. Since there are no individual neurons with a double-peaked duration response profile, both types of temporal processing seem to be well segregated in the IC. Most short- and band-pass units with best frequency in the CF2 range responded to best duratio... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488565 Thu, 08 Dec 2011 05:00:00 +0100 5488565 http://www.medworm.com/index.php?rid=5488564&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3102%3Frss%3D1 While peripheral sensory neurons respond to natural stimuli with a broad range of spatiotemporal frequencies, central neurons instead respond sparsely to specific features in general. The nonlinear transformations leading to this emergent selectivity are not well understood. Here we characterized how the neural representation of stimuli changes across successive brain areas, using the electrosensory system of weakly electric fish as a model system. We found that midbrain torus semicircularis (TS) neurons were on average more selective in their responses than hindbrain electrosensory lateral line lobe (ELL) neurons. Further analysis revealed two categories of TS neurons: dense coding TS neurons that were ELL-like and sparse coding TS neurons that displayed selective responses. These neurons... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488564 Thu, 08 Dec 2011 05:00:00 +0100 5488564 http://www.medworm.com/index.php?rid=5488563&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3091%3Frss%3D1 In environments containing sensory events at competing locations, selecting a target for orienting requires prioritization of stimulus values. Although the superior colliculus (SC) is causally linked to the stimulus selection process, the manner in which SC multisensory integration operates in a competitive stimulus environment is unknown. Here we examined how the activity of visual-auditory SC neurons is affected by placement of a competing target in the opposite hemifield, a stimulus configuration that would, in principle, promote interhemispheric competition for access to downstream motor circuitry. Competitive interactions between the targets were evident in how they altered unisensory and multisensory responses of individual neurons. Responses elicited by a cross-modal stimulus (multi... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488563 Thu, 08 Dec 2011 05:00:00 +0100 5488563 http://www.medworm.com/index.php?rid=5488562&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3082%3Frss%3D1 Clinical and experimental research has demonstrated that the emotional experience of fear and anxiety impairs postural stability in humans. The current study investigated whether changes in fear and anxiety can also modulate spinal stretch reflexes and the gain of afferent inputs to the primary somatosensory cortex. To do so, two separate experiments were performed on two separate groups of participants while they stood under conditions of low and high postural threat. In experiment 1, the proprioceptive system was probed using phasic mechanical stimulation of the Achilles tendon while simultaneously recording the ensuing tendon reflexes in the soleus muscle and cortical-evoked potentials over the somatosensory cortex during low and high threat conditions. In experiment 2, phasic electrica... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488562 Thu, 08 Dec 2011 05:00:00 +0100 5488562 http://www.medworm.com/index.php?rid=5488561&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3073%3Frss%3D1 Gonadotropin-releasing hormone (GnRH) neurons form the final common pathway for central control of fertility. Regulation of GnRH neurons by long-loop gonadal steroid feedback through steroid receptor-expressing afferents such as GABAergic neurons is well studied. Recently, local central feedback circuits regulating GnRH neurons were identified. GnRH neuronal depolarization induces short-term inhibition of their GABAergic afferents via a mechanism dependent on metabotropic glutamate receptor (mGluR) activation. GnRH neurons are enveloped in astrocytes, which express mGluRs. GnRH neurons also produce endocannabinoids, which can be induced by mGluR activation. We hypothesized the local GnRH-GABA circuit utilizes glia-derived and/or cannabinoid mechanisms and is altered by steroid milieu. Whol... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488561 Thu, 08 Dec 2011 05:00:00 +0100 5488561 http://www.medworm.com/index.php?rid=5488560&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3067%3Frss%3D1 Chronic compression (CCD) of the dorsal root ganglion (DRG) is a model of human radicular pain produced by intraforaminal stenosis and other disorders affecting the DRG, spinal nerve, or root. Previously, we examined electrophysiological changes in small-diameter lumbar level 3 (L3) and L4 DRG neurons treated with CCD; the present study extends these observations to medium-sized DRG neurons, which mediate additional sensory modalities, both nociceptive and non-nociceptive. Whole-cell patch-clamp recordings were obtained from medium-sized somata in the intact DRG in vitro. Compared with neurons from unoperated control animals, CCD neurons exhibited a decrease in the current threshold for action potential generation. In the CCD group, current densities of TTX-resistant and TTX-sensitive Na+ ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488560 Thu, 08 Dec 2011 05:00:00 +0100 5488560 http://www.medworm.com/index.php?rid=5488559&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3056%3Frss%3D1 The cold-sensing channel transient receptor potential melastatin 8 (TRPM8) features Ca2+-dependent downregulation, a cellular process underlying somatosensory accommodation in cold environments. The Ca2+-dependent functional downregulation of TRPM8 is manifested with two distinctive phases, acute desensitization and tachyphylaxis. Here we show in rat dorsal root ganglion neurons that TRPM8 acute desensitization critically depends on phosphatidylinositol 4,5-bisphosphate (PIP2) availability rather than PIP2 hydrolysis and is triggered by calmodulin activation. Tachyphylaxis, on the other hand, is mediated by phospholipase hydrolysis of PIP2 and protein kinase C/phosphatase 1,2A. We further demonstrate that PIP2 switches TRPM8 channel gating to a high-open probability state with short closed... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488559 Thu, 08 Dec 2011 05:00:00 +0100 5488559 http://www.medworm.com/index.php?rid=5488558&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3045%3Frss%3D1 Reactive oxygen species (ROS) modulate neuronal excitability. In the present study we examined the effects of hydrogen peroxide (H2O2), a well established ROS, on neuronal activity from two neonatal mouse brain regions, i.e., the pre-Bötzinger complex (preBötC) within the ventral respiratory column (VRC) and the CA1 area of the hippocampus. In the preBötC, 2.2 mM H2O2 evoked a transient depression followed by augmentation of neuronal activity. The iron chelator deferoxamine (500 μM) did not prevent H2O2-mediated neuronal augmentation but prevented the initial depression. Combined application of Fe2+ and H2O2 only caused depression of the preBötC rhythm. In contrast, H2O2 suppressed neuronal activity in the CA1 region, and this effect was accentuated by coapplication ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488558 Thu, 08 Dec 2011 05:00:00 +0100 5488558 http://www.medworm.com/index.php?rid=5488557&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3035%3Frss%3D1 Alternating epochs of activity and silence are a characteristic feature of neocortical networks during certain sleep cycles and deep states of anesthesia. The mechanism and functional role of these slow oscillations (<1 Hz) have not yet been fully characterized. Experimental and theoretical studies show that slow-wave oscillations can be generated autonomously by neocortical tissue but become more regular through a thalamo-cortical feedback loop. Evidence for a functional role of slow-wave activity comes from EEG recordings in humans during sleep, which show that activity travels as stereotypical waves over the entire brain, thought to play a role in memory consolidation. We used an animal model to investigate activity wave propagation on a smaller scale, namely within the rat somatosen... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488557 Thu, 08 Dec 2011 05:00:00 +0100 5488557 http://www.medworm.com/index.php?rid=5488556&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3019%3Frss%3D1 GABA projection neurons (GABA neurons) in the substantia nigra pars reticulata (SNr) and dopamine projection neurons (DA neurons) in substantia nigra pars compacta (SNc) have strikingly different firing properties. SNc DA neurons fire low-frequency, long-duration spikes, whereas SNr GABA neurons fire high-frequency, short-duration spikes. Since voltage-activated sodium (NaV) channels are critical to spike generation, the different firing properties raise the possibility that, compared with DA neurons, NaV channels in SNr GABA neurons have higher density, faster kinetics, and less cumulative inactivation. Our quantitative RT-PCR analysis on immunohistochemically identified nigral neurons indicated that mRNAs for pore-forming NaV1.1 and NaV1.6 subunits and regulatory NaVβ1 and Navβ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488556 Thu, 08 Dec 2011 05:00:00 +0100 5488556 http://www.medworm.com/index.php?rid=5488555&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3010%3Frss%3D1 In this report we provide modeling evidence that cyclic physiological activation of astroglial cells produces similar BOLD oscillations through a mechanism mediated by intracellular Ca2+ signaling. Specifically, neurotransmission induces pulses of Ca2+ concentration in astrocytes, resulting in increased cerebral perfusion and neuroactive transmitter release by these cells (i.e., gliotransmission), which in turn stimulates neuronal activity. Noticeably, the level of neuron-astrocyte cross talk regulates the periodic behavior of the Ca2+ wave-induced BOLD fluctuations. Our results suggest that the spontaneous ongoing activity of neuroglial networks is a potential source of the observed slow fMRI signal oscillations. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488555 Thu, 08 Dec 2011 05:00:00 +0100 5488555 http://www.medworm.com/index.php?rid=5488554&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F3001%3Frss%3D1 During priming of pop-out, performance at discriminating a pop-out feature target in visual search is affected by whether the target on the previous trial was defined by the same feature as on the upcoming trial. Recent studies suggest that priming of pop-out relies on attentional processes. With the use of simultaneous, combined transcranial magnetic stimulation and event-related potential recording (TMS-ERP), we tested for any critical role of the right angular gyrus (rANG) and left and right frontal eye fields (FEFs)—key attentional sites—in modulating both performance and the ERPs evoked by such visual events. Intertrial TMS trains were applied while participants discriminated the orientation of a color pop-out element in a visual search array. rANG TMS disrupted priming of... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488554 Thu, 08 Dec 2011 05:00:00 +0100 5488554 http://www.medworm.com/index.php?rid=5488553&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2992%3Frss%3D1 Since the environment is in constant flux, decision-making capabilities of the brain must be rapid and flexible. Yet in sensory motion processing pathways of the primate brain where decision making has been extensively studied, the flexibility of neurons is limited by inherent selectivity to motion direction and speed. The supplementary eye field (SEF), an area involved in decision making on moving stimuli, is not strictly a sensory or motor structure, and hence may not suffer such limitations. Here we test whether neurons in the SEF can flexibly interpret the rule of a go/nogo task when the decision boundary in the task changes with each trial. The task rule specified that the animal pursue a moving target with its eyes if and when the target entered a visible zone. The size of the zone w... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488553 Thu, 08 Dec 2011 05:00:00 +0100 5488553 http://www.medworm.com/index.php?rid=5488552&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2982%3Frss%3D1 Geniculate ganglion (GG) cell bodies of chorda tympani (CT), greater superficial petrosal (GSP), and posterior auricular (PA) nerves transmit orofacial sensory information to the rostral nucleus of the solitary tract. We have used whole cell recording to investigate the characteristics of the Na+ channels in isolated Fluorogold-labeled GG neurons that innervate different peripheral receptive fields. GG neurons expressed two classes of Na+ channels, TTX sensitive (TTX-S) and TTX resistant (TTX-R). The majority of GG neurons expressed TTX-R currents of different amplitudes. TTX-R currents were relatively small in 60% of the neurons but were large in 12% of the sampled population. In a further 28% of the neurons, TTX completely abolished all Na+ currents. Application of TTX completely inhibit... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488552 Thu, 08 Dec 2011 05:00:00 +0100 5488552 http://www.medworm.com/index.php?rid=5488551&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2973%3Frss%3D1 Manipulating a cup by the handle requires compensating for the torque induced by the moment of the mass of the cup relative to the location of the handle. In the present study, we investigated the control strategy of subjects asked to perform grip-lift movements with an object with center of mass located away from the grip axis. Participants were asked to lift the manipulandum with a two-fingers precision grip and stabilize it in front of a visual target. Subjects showed a gradual and slow adaptation of the grip-force scaling across trials: the grip force tended to decrease slowly, and the temporal coordination between grip-force and load-torque rates displayed gradually, better-coordinated patterns. Importantly, this adaptation was much slower than the stabilization of the same parameters... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488551 Thu, 08 Dec 2011 05:00:00 +0100 5488551 http://www.medworm.com/index.php?rid=5488550&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2964%3Frss%3D1 Recent studies have associated increasing temporal expectations with synchronization of higher frequency oscillations and suppression of lower frequencies. In this experiment, we explore a proposal that low-frequency oscillations provide a mechanism for regulating temporal expectations. We used a speeded Go/No-go task and manipulated temporal expectations by changing the probability of target presentation after certain intervals. Across two conditions, the temporal conditional probability of target events differed substantially at the first of three possible intervals. We found that reactions times differed significantly at this first interval across conditions, decreasing with higher temporal expectations. Interestingly, the power of theta activity (4–8 Hz), distributed over central... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488550 Thu, 08 Dec 2011 05:00:00 +0100 5488550 http://www.medworm.com/index.php?rid=5488549&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2950%3Frss%3D1 Spatial and temporal properties of head movement are encoded by vestibular hair cells in the inner ear. One of the most striking features of these receptors is the orderly structural variation in their mechanoreceptive hair bundles, but the functional significance of this diversity is poorly understood. We tested the hypothesis that hair bundle structure is a significant contributor to hair bundle mechanics by comparing structure and steady-state stiffness of 73 hair bundles at varying locations on the utricular macula. Our first major finding is that stiffness of utricular hair bundles varies systematically with macular locus. Stiffness values are highest in the striola, near the line of hair bundle polarity reversal, and decline exponentially toward the medial extrastriola. Striolar bund... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488549 Thu, 08 Dec 2011 05:00:00 +0100 5488549 http://www.medworm.com/index.php?rid=5488548&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2936%3Frss%3D1 Striatal fast-spiking (FS) cells in slices fire in the gamma frequency range and in vivo are often phase-locked to gamma oscillations in the field potential. We studied the firing patterns of these cells in slices from rats ages 16–23 days to determine the mechanism of their gamma resonance. The resonance of striatal FS cells was manifested as a minimum frequency for repetitive firing. At rheobase, cells fired a doublet of action potentials or doublets separated by pauses, with an instantaneous firing rate averaging 44 spikes/s. The minimum rate for sustained firing was also responsible for the stuttering firing pattern. Firing rate adapted during each episode of firing, and bursts were terminated when firing was reduced to the minimum sustainable rate. Resonance and stuttering conti... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488548 Thu, 08 Dec 2011 05:00:00 +0100 5488548 http://www.medworm.com/index.php?rid=5488547&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2922%3Frss%3D1 Light hyperpolarizes cone photoreceptors, causing synaptic voltage-gated Ca2+ channels to open infrequently. To understand neurotransmission under these conditions, we determined the number of L-type Ca2+ channel openings necessary for vesicle fusion at the cone ribbon synapse. Ca2+ currents (ICa) were activated in voltage-clamped cones, and excitatory postsynaptic currents (EPSCs) were recorded from horizontal cells in the salamander retina slice preparation. Ca2+ channel number and single-channel current amplitude were calculated by mean-variance analysis of ICa. Two different comparisons—one comparing average numbers of release events to average ICa amplitude and the other involving deconvolution of both EPSCs and simultaneously recorded cone ICa—suggested that fewer than th... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488547 Thu, 08 Dec 2011 05:00:00 +0100 5488547 http://www.medworm.com/index.php?rid=5488546&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2910%3Frss%3D1 This study allows us to carry out interareal comparisons and provides a baseline to compare against cortical emerging activity from genetically altered animals. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488546 Thu, 08 Dec 2011 05:00:00 +0100 5488546 http://www.medworm.com/index.php?rid=5488545&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2896%3Frss%3D1 Perceptual objects often comprise a visual and auditory signature that arrives simultaneously through distinct sensory channels, and cross-modal features are linked by virtue of being attributed to a specific object. Continued exposure to cross-modal events sets up expectations about what a given object most likely "sounds" like, and vice versa, thereby facilitating object detection and recognition. The binding of familiar auditory and visual signatures is referred to as semantic, multisensory integration. Whereas integration of semantically related cross-modal features is behaviorally advantageous, situations of sensory dominance of one modality at the expense of another impair performance. In the present study, magnetoencephalography recordings of semantically related cross-modal and uni... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488545 Thu, 08 Dec 2011 05:00:00 +0100 5488545 http://www.medworm.com/index.php?rid=5488544&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2888%3Frss%3D1 This study provides a sense of how the nodal centralities of the human resting state MEG are distributed at the sensor level and how reliable they are. It also provides a fundamental scientific background for continued examination of the resting state of human MEG. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488544 Thu, 08 Dec 2011 05:00:00 +0100 5488544 http://www.medworm.com/index.php?rid=5488543&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2876%3Frss%3D1 In this study we tested the role of astrocyte function in reactive synaptogenesis in the trigeminal principal nucleus (PrV) of neonatal rats following unilateral transection of the infraorbital (IO) branch of the trigeminal nerve. We used electrophysiological multiple input index analysis (MII) to estimate the number of central trigeminal afferent fibers that converge onto single barrelette neurons. In the developing PrV, about 30% of afferent connections are eliminated within 2 postnatal weeks. After neonatal IO nerve damage, multiple trigeminal inputs (2.7 times that of the normal inputs) converge on single barrelette cells within 3–5 days; they remain stable up to the second postnatal week. Astrocyte proliferation and upregulation of astrocyte-specific proteins (GFAP and ALDH1L1) ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488543 Thu, 08 Dec 2011 05:00:00 +0100 5488543 http://www.medworm.com/index.php?rid=5488542&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2865%3Frss%3D1 In this study, we assessed the expression and functional properties of TRPM2 channels in rat dopaminergic SNc neurons, using acute brain slices. RT-PCR analysis revealed TRPM2 mRNA expression in the SNc region. Immunohistochemistry demonstrated expression of TRPM2 protein in tyrosine hydroxylase-positive neurons. Channel function was tested with whole cell patch-clamp recordings and calcium (fura-2) imaging. Intracellular application of ADP-ribose (50–400 μM) evoked a dose-dependent, desensitizing inward current and intracellular free calcium concentration ([Ca2+]i) rise. These responses were strongly inhibited by the nonselective TRPM2 channel blockers clotrimazole and flufenamic acid. Exogenous application of H2O2 (1–5 mM) evoked a rise in [Ca2+]i and an outward current ma... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488542 Thu, 08 Dec 2011 05:00:00 +0100 5488542 http://www.medworm.com/index.php?rid=5488541&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2849%3Frss%3D1 Dexterous use of the hand represents a sophisticated sensorimotor function. In behaviors such as playing the piano, it can involve strong temporal and spatial constraints. The purpose of this study was to determine fundamental patterns of covariation of motion across joints and digits of the human hand. Joint motion was recorded while 5 expert pianists played 30 excerpts from musical pieces, which featured ~50 different tone sequences and fingering. Principal component analysis and cluster analysis using an expectation-maximization algorithm revealed that joint velocities could be categorized into several patterns, which help to simplify the description of the movements of the multiple degrees of freedom of the hand. For the thumb keystroke, two distinct patterns of joint movement covariat... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488541 Thu, 08 Dec 2011 05:00:00 +0100 5488541 http://www.medworm.com/index.php?rid=5488540&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F106%2F6%2F2838%3Frss%3D1 Peripheral nerve inflammation can cause neuronal excitability changes that have been implicated in the pathogenesis of chronic pain. Although the neuroimmune interactions that lead to such physiological changes are unclear, in vitro studies suggest that the chemokine CCL2 may be involved. This in vivo study examines the effects of CCL2 on untreated and inflamed neurons and compares its effects with those of TNF-α. Extracellular recordings were performed in the anesthetized rat on isolated neurons with C-fiber axons. On untreated neurons, CCL2, as well as TNF-α, had negligible effects. Following neuritis, both cytokines transiently caused the firing of action potentials in 27–30% of neurons, which were either silent or had background (ongoing) activity. The neurons with on... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=5488540 Thu, 08 Dec 2011 05:00:00 +0100 5488540