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. Sun, 21 Mar 2010 15:31:09 +0100 http://www.medworm.com/index.php?rid=3372082&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Ffull%2F103%2F3%2F1705%3Frss%3D1 (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372082 Tue, 16 Mar 2010 15:19:51 +0100 3372082 http://www.medworm.com/index.php?rid=3372081&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1696%3Frss%3D1 We describe the recording approach and the parameters of the electric configuration underlying nanostimulation. We use glass pipettes with a DC resistance of 4–7 M. Obtaining the juxtacellular configuration requires a close contact between pipette tip and neuron and is associated with a several-fold increase in resistance to values ≥20 M. The recorded action potential (AP) amplitude grows to ≥2 mV, and neurons can be activated with currents in the nanoampere range—hence the term nanostimulation. While exact AP timing has not been achieved, AP frequency and AP number can be parametrically controlled. We demonstrate that nanostimulation can also be used to selectively inhibit sensory responses in identifiable neurons. Nanostimulation is biophysically similar to electroporat... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372081 Tue, 16 Mar 2010 15:19:50 +0100 3372081 http://www.medworm.com/index.php?rid=3372080&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1685%3Frss%3D1 In this study, we compared the influence of two types of reflex blinks on the trajectories and kinematics of memory-guided saccades in human subjects. We found that electrical stimulation of the supraorbital nerve shortly before or during a saccade briefly halts or decelerates the eye in midflight. After this short interruption, the eye always resumed its course and reached the target location in the absence of visual feedback. Air puff stimuli produced significant decreases in mean eye velocity too, but in addition to these changes in saccade kinematics, they produced much larger and more variable perturbations of the two-dimensional saccade trajectories. Even so, the endpoints of blink-perturbed saccades obtained under both test conditions remained as accurate and as precise as those obs... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372080 Tue, 16 Mar 2010 15:19:50 +0100 3372080 http://www.medworm.com/index.php?rid=3372079&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1673%3Frss%3D1 In adults, locomotor movements are accommodated to various support surface conditions by means of specific anticipatory locomotor adjustments and changes in the intersegmental coordination. Here we studied the kinematic strategies of toddlers at the onset of independent walking when negotiating various support surface conditions: stepping over an obstacle, walking on an inclined surface, and on a staircase. Generally, toddlers could perform these tasks only when supported by the arm. They exhibited strategies very different from those of the adults. Although adults maintained walking speed roughly constant, toddlers markedly accelerated when walking downhill or downstairs and decelerated when walking uphill or upstairs. Their coordination pattern of thigh–shank–foot elevation a... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372079 Tue, 16 Mar 2010 15:19:50 +0100 3372079 http://www.medworm.com/index.php?rid=3372078&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1658%3Frss%3D1 Oscillations of local field potentials (LFPs) in the gamma range are found in many brain regions and are supposed to support the temporal organization of cognitive, perceptual, and motor functions. Even though gamma oscillations have also been observed in ventral striatum, one of the brain's most important structures for motivated behavior and reward processing, their specific function during ongoing behavior is unknown. Using a movable tetrode array, we recorded LFPs and activity of neural ensembles in the ventral striatum of rats performing a reward-collection task. Rats were running along a triangle track and in each round collected one of three different types of rewards. The gamma power of LFPs on subsets of tetrodes was modulated by reward-site visits, discriminated between reward ty... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372078 Tue, 16 Mar 2010 15:19:50 +0100 3372078 http://www.medworm.com/index.php?rid=3372077&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1646%3Frss%3D1 Motion vision is essential for navigating through the environment. Due to its genetic amenability, the fruit fly Drosophila has been serving for a lengthy period as a model organism for studying optomotor behavior as elicited by large-field horizontal motion. However, the neurons underlying the control of this behavior have not been studied in Drosophila so far. Here we report the first whole cell recordings from three cells of the horizontal system (HSN, HSE, and HSS) in the lobula plate of Drosophila. All three HS cells are tuned to large-field horizontal motion in a direction-selective way; they become excited by front-to-back motion and inhibited by back-to-front motion in the ipsilateral field of view. The response properties of HS cells such as contrast and velocity dependence are in... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372077 Tue, 16 Mar 2010 15:19:50 +0100 3372077 http://www.medworm.com/index.php?rid=3372076&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1630%3Frss%3D1 Manual dexterity, a prerogative of primates, is under the control of the corticospinal (CS) tract. Because 90–95% of CS axons decussate, it is assumed that this control is exerted essentially on the contralateral hand. Consistently, unilateral lesion of the hand representation in the motor cortex is followed by a complete loss of dexterity of the contralesional hand. During the months following lesion, spontaneous recovery of manual dexterity takes place to a highly variable extent across subjects, although largely incomplete. In the present study, we tested the hypothesis that after a significant postlesion period, manual performance in the ipsilesional hand is correlated with the extent of functional recovery in the contralesional hand. To this aim, ten adult macaque monkeys were s... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372076 Tue, 16 Mar 2010 15:19:50 +0100 3372076 http://www.medworm.com/index.php?rid=3372075&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1622%3Frss%3D1 The parasternal intercostal muscles are obligatory inspiratory muscles. To test the hypothesis that they are also involved in trunk rotation and to assess the effect of any postural role on inspiratory drive to the muscles, intramuscular electromyographic (EMG) recordings were made from the parasternal intercostals on the right side in six healthy subjects during resting breathing in a neutral posture ("neutral breaths"), during an isometric axial rotation effort of the trunk to the right ("ipsilateral rotation") or left ("contralateral rotation"), and during resting breathing with the trunk rotated. The parasternal intercostals were commonly active during ipsilateral rotation but were consistently silent during contralateral rotation. In addition, with ipsilateral rotation, peak parastern... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372075 Tue, 16 Mar 2010 15:19:50 +0100 3372075 http://www.medworm.com/index.php?rid=3372074&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1614%3Frss%3D1 Auditory receptor neurons of crickets are most sensitive to either low or high sound frequencies. Earlier work showed that the temporal coding properties of first-order auditory interneurons are matched to the temporal characteristics of natural low- and high-frequency stimuli (cricket songs and bat echolocation calls, respectively). We studied the temporal coding properties of receptor neurons and used modeling to investigate how activity within populations of low- and high-frequency receptors might contribute to the coding properties of interneurons. We confirm earlier findings that individual low-frequency-tuned receptors code stimulus temporal pattern poorly, but show that coding performance of a receptor population increases markedly with population size, due in part to low redundancy... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372074 Tue, 16 Mar 2010 15:19:50 +0100 3372074 http://www.medworm.com/index.php?rid=3372073&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1606%3Frss%3D1 External transients, such as a flash or a startling sound, are believed to capture attention. Bauer, Cheadle, Parton, Müller, and Usher reported that attention can also be captured by a stimulus that flickers subliminally at 50 Hz, presumably by entrainment of neurons to the flicker frequency. In their reaction time (RT) task, participants had to locate a subtle change in the spatial frequency content of one of three Gabors (the target). Prior to target onset, presumably subliminal 50-Hz flicker in one of the Gabors served as a spatial cue. Bauer et al. found faster RTs when the cued location was congruent with the target location than when the cue was incongruent with the target location. In their experiments, the cue stopped to flicker at 50 Hz at target onset and was replaced by a ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372073 Tue, 16 Mar 2010 15:19:50 +0100 3372073 http://www.medworm.com/index.php?rid=3372072&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1591%3Frss%3D1 Hip position and loading of limb extensors are major sensory cues for the initiation and duration of different phases during walking. Although these inputs have pathways projecting to the locomotor rhythm generator, their effects may vary in different parts of the locomotor cycle. In the present study, the plantaris (Pl), sartorius (Sart), rectus femoris (RF), and caudal gluteal (cGlu) nerves were stimulated at group I and/or group II strength during spontaneous fictive locomotion in 16 adult decerebrate cats. These nerves supply muscles that extend the ankle (Pl), flex the hip (Sart, RF), or extend the hip (cGlu). Stimuli were given at six epochs of the locomotor cycle to evaluate when they access the rhythm generator. Group I afferents from Pl nerve always reset the locomotor rhythm; sti... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372072 Tue, 16 Mar 2010 15:19:50 +0100 3372072 http://www.medworm.com/index.php?rid=3372071&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1580%3Frss%3D1 Previous studies have demonstrated that "locomotor-like" rhythmic patterns can be evoked in the isolated neonatal rat spinal cord by several means, including pharmacological neuromodulation and electrical stimulation of various pathways. Recent studies have used stimulation of afferent pathways to evoke rhythmic patterns, relying on synaptic activation of interneuronal systems rather than global imposition of neuromodulatory state by pharmacological agents. We use the in vitro neonatal rat spinal cord with attached hindlimb to examine the muscle activation patterns evoked by stimulation of these different pathways and evaluate whether stimulation of these pathways all evoke the same patterns. We find that the patterns evoked by bath application of serotonin (5-HT) and N-methyl-d-aspartic a... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372071 Tue, 16 Mar 2010 15:19:50 +0100 3372071 http://www.medworm.com/index.php?rid=3372070&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1569%3Frss%3D1 Human neuroimaging studies have implicated a number of brain regions in long-term memory formation. Foremost among these is ventrolateral prefrontal cortex. Here, we used double-pulse transcranial magnetic stimulation (TMS) to assess whether the contribution of this part of cortex is crucial for laying down new memories and, if so, to examine the time course of this process. Healthy adult volunteers performed an incidental encoding task (living/nonliving judgments) on sequences of words. In separate series, the task was performed either on its own or while TMS was applied to one of two sites of experimental interest (left/right anterior inferior frontal gyrus) or a control site (vertex). TMS pulses were delivered at 350, 750, or 1,150 ms following word onset. After a delay of 15 min, memor... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372070 Tue, 16 Mar 2010 15:19:50 +0100 3372070 http://www.medworm.com/index.php?rid=3372069&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1557%3Frss%3D1 The purpose of this study was to quantify how volitional control of hip torque relates to walking function poststroke. Volitional phasing of hip flexion and extension torques was assessed using a load-cell-instrumented servomotor drive system in 11 chronic stroke subjects and 5 age-matched controls. Hips were oscillated from ~40° of hip flexion to 10° of hip extension at a frequency of 0.50 Hz during three movement conditions [hips in phase (IP), 180° out of phase (OP), and unilateral hip movement (UN)] while the knees and ankles were held stationary. The magnitude and phasing of hip, knee, and ankle torques were measured during each movement condition. Surface electromyography was measured throughout the legs. Over ground gait analysis was done for all stroke subjects. During ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372069 Tue, 16 Mar 2010 15:19:50 +0100 3372069 http://www.medworm.com/index.php?rid=3372068&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1543%3Frss%3D1 Ion channels may be gated by Ca2+ entering from the extracellular space or released from intracellular stores—typically the endoplasmic reticulum. The present study examines how Ca2+ impacts ion channels in the bag cell neurons of Aplysia californica. These neuroendocrine cells trigger ovulation through an afterdischarge involving Ca2+ influx from Ca2+ channels and Ca2+ release from both the mitochondria and endoplasmic reticulum. Liberating mitochondrial Ca2+ with the protonophore, carbonyl cyanide-4-trifluoromethoxyphenyl-hydrazone (FCCP), depolarized bag cell neurons, whereas depleting endoplasmic reticulum Ca2+ with the Ca2+-ATPase inhibitor, cyclopiazonic acid, did not. In a concentration-dependent manner, FCCP elicited an inward current associated with an increase in conductanc... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372068 Tue, 16 Mar 2010 15:19:50 +0100 3372068 http://www.medworm.com/index.php?rid=3372067&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1532%3Frss%3D1 This study investigates the possibility of describing a multijoint reaching task of the upper limb by a linear combination of one set of muscle synergies common to multiple directions. Surface electromyographic (EMG) signals were recorded from 12 muscles of the dominant upper limb of eight healthy men during single-joint movements and a multijoint reaching task in 12 directions in the horizontal plane. The movement kinematics was recorded by a motion analysis system. Muscle synergies were extracted with nonnegative matrix factorization of the EMG envelopes. Synergies were computed either from the single-joint movements to describe the two degrees of freedom independently or from the multijoint movements. On average, the multijoint reaching task could be accurately described in all the dire... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372067 Tue, 16 Mar 2010 15:19:50 +0100 3372067 http://www.medworm.com/index.php?rid=3372066&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1518%3Frss%3D1 Which is heavier: a pound of lead or a pound of feathers? This classic trick question belies a simple but surprising truth: when lifted, the pound of lead feels heavier—a phenomenon known as the size–weight illusion. To estimate the weight of an object, our CNS combines two imperfect sources of information: a prior expectation, based on the object's appearance, and direct sensory information from lifting it. Bayes' theorem (or Bayes' law) defines the statistically optimal way to combine multiple information sources for maximally accurate estimation. Here we asked whether the mechanisms for combining these information sources produce statistically optimal weight estimates for both perceptions and actions. We first studied the ability of subjects to hold one hand steady when the ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372066 Tue, 16 Mar 2010 15:19:50 +0100 3372066 http://www.medworm.com/index.php?rid=3372065&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1508%3Frss%3D1 The same visual stimulus evokes a different pattern of neural signals each time the stimulus is presented. Because this unreliability reduces visual performance, it is important to understand how it arises from neural circuitry. We asked whether different types of ganglion cell receive excitatory signals with different reliability and frequency content and, if so, how retinal circuitry contributes to these differences. If transmitter release is governed by Poisson statistics, the SNR of the postsynaptic currents (ratio of signal power to noise power) should grow linearly with quantal rate (qr), a prediction that we confirmed experimentally. Yet ganglion cells of the same type receive quanta at different rates. Thus to obtain a measure of reliability independent of quantal rate, we calculat... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372065 Tue, 16 Mar 2010 15:19:50 +0100 3372065 http://www.medworm.com/index.php?rid=3372064&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1501%3Frss%3D1 Early retinotopic cortex has traditionally been viewed as containing a veridical representation of the low-level properties of the image, not imbued by high-level interpretation and meaning. Yet several recent results indicate that neural representations in early retinotopic cortex reflect not just the sensory properties of the image, but also the perceived size and brightness of image regions. Here we used functional magnetic resonance imaging pattern analyses to ask whether the representation of an object in early retinotopic cortex changes when the object is recognized compared with when the same stimulus is presented but not recognized. Our data confirmed this hypothesis: the pattern of response in early retinotopic visual cortex to a two-tone "Mooney" image of an object was more simil... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372064 Tue, 16 Mar 2010 15:19:50 +0100 3372064 http://www.medworm.com/index.php?rid=3372063&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1490%3Frss%3D1 We examined whether local recurrent excitatory synaptic connections form between dentate granule cells in mice 8–12 wk after cortical contusion injury. Mice were monitored for behavioral seizures shortly after brain injury and ≤10 wk postinjury. Injury-induced seizures were observed in 15% of mice, and spontaneous seizures were observed weeks later in 40% of mice. Timm's staining revealed mossy fiber sprouting into the inner molecular layer of the dorsal dentate gyrus ipsilateral to the injury in 95% of mice but not contralateral to the injury or in uninjured controls. Whole cell patch-clamp recordings were made from granule cells in isolated hippocampal brain slices. Cells in slices with posttraumatic mossy fiber sprouting had an increased excitatory postsynaptic current (EPSC) f... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372063 Tue, 16 Mar 2010 15:19:49 +0100 3372063 http://www.medworm.com/index.php?rid=3372062&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1478%3Frss%3D1 In this study, foot movements of PD and normal subjects were monitored with an OPTOTRAK motion-detection system while they walked on a treadmill at different velocities. PD subjects were also paced with auditory stimuli at different frequencies. PD gait was characterized by step frequencies that were faster and stride lengths that were shorter than those of normal controls. At low walking velocities, PD stepping had a reduced or absent terminal toe lift, which truncated swing phases, producing shortened steps. Auditory pacing was not able to normalize step frequency at these lower velocities. Peak forward toe velocities increased with walking velocity and PD subjects could initiate appropriate foot dynamics during initial phases of the swing. They could not control the foot appropriately i... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372062 Tue, 16 Mar 2010 15:19:49 +0100 3372062 http://www.medworm.com/index.php?rid=3372061&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1467%3Frss%3D1 People are easily able to perceive the human body across different viewpoints, but the neural mechanisms underpinning this ability are currently unclear. In three experiments, we used functional MRI (fMRI) adaptation to study the view-invariance of representations in two cortical regions that have previously been shown to be sensitive to visual depictions of the human body—the extrastriate and fusiform body areas (EBA and FBA). The BOLD response to sequentially presented pairs of bodies was treated as an index of view invariance. Specifically, we compared trials in which the bodies in each image held identical poses (seen from different views) to trials containing different poses. EBA and FBA adapted to identical views of the same pose, and both showed a progressive rebound from adap... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372061 Tue, 16 Mar 2010 15:19:49 +0100 3372061 http://www.medworm.com/index.php?rid=3372060&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1456%3Frss%3D1 AII amacrine cells in the mammalian retina are connected via electrical synapses to on-cone bipolar cells and to other AII amacrine cells. To understand synaptic integration in these interneurons, we need information about the junctional conductance (gj), the membrane resistance (rm), the membrane capacitance (Cm), and the cytoplasmic resistivity (Ri). Due to the extensive electrical coupling, it is difficult to obtain estimates of rm, as well as the relative contribution of the junctional and nonjunctional conductances to the total input resistance of an AII amacrine cell. Here we used dual voltage-clamp recording of pairs of electrically coupled AII amacrine cells in an in vitro slice preparation from rat retina and applied meclofenamic acid (MFA) to block the electrical coupling and iso... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372060 Tue, 16 Mar 2010 15:19:49 +0100 3372060 http://www.medworm.com/index.php?rid=3372059&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1448%3Frss%3D1 The inner ear can produce sounds, but how these otoacoustic emissions back-propagate through the cochlea is currently debated. Two opposing views exist: fast pressure waves in the cochlear fluids and slow traveling waves involving the basilar membrane. Resolving this issue requires measuring the travel times of emissions from their cochlear origin to the ear canal. This is problematic because the exact intracochlear location of emission generation is unknown and because the cochlea is vulnerable to invasive measurements. We employed a multi-tone stimulus optimized to measure reverse travel times. By exploiting the dispersive nature of the cochlea and by combining acoustic measurements in the ear canal with recordings of the cochlear-microphonic potential, we were able to determine the grou... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372059 Tue, 16 Mar 2010 15:19:49 +0100 3372059 http://www.medworm.com/index.php?rid=3372058&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1438%3Frss%3D1 It is well known that pro- and antisaccades may deploy different cognitive processes. However, the specific reason why antisaccades have longer latencies than prosaccades is still under debate. In three experiments, we studied the factors contributing to the antisaccade cost by taking attentional orienting and target location probabilities into account. In experiment 1, using a new antisaccade paradigm, we directly tested Olk and Kingstone's hypothesis, which attributes longer antisaccade latency to the time it takes to reorient from the visual target to the opposite saccadic target. By eliminating the reorienting component in our paradigm, we found no significant difference between the latencies of the two saccade types. In experiment 2, we varied the proportion of prosaccades made to cer... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372058 Tue, 16 Mar 2010 15:19:49 +0100 3372058 http://www.medworm.com/index.php?rid=3372057&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1431%3Frss%3D1 In this study, we use patch-clamp recording and calcium imaging to explore the properties of glutamate receptors expressed by NPCs in the olfactory bulb subependymal layer. We find that calcium-permeable AMPA receptors (AMPARs) are the major receptor type underlying glutamatergic signaling in olfactory bulb NPCs. We also show that when transmitter uptake is reduced, glutamate spillover from distant nerve terminals in the olfactory bulb can activate nonsynaptic NPC AMPARs and generate increases in intracellular calcium. Together, these results suggest that Ca2+ influx via AMPARs may contribute to calcium-dependent processes that govern NPC differentiation and maturation. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372057 Tue, 16 Mar 2010 15:19:49 +0100 3372057 http://www.medworm.com/index.php?rid=3372056&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1425%3Frss%3D1 Humans can efficiently store fine-detailed facial emotional information in visual short-term memory for several seconds. However, an unresolved question is whether the same neural mechanisms underlie high-fidelity short-term memory for emotional expressions at different retention intervals. Here we show that retention interval affects the neural processes of short-term memory encoding using a delayed facial emotion discrimination task. The early sensory P100 component of the event-related potentials (ERP) was larger in the 1-s interstimulus interval (ISI) condition than in the 6-s ISI condition, whereas the face-specific N170 component was larger in the longer ISI condition. Furthermore, the memory-related late P3b component of the ERP responses was also modulated by retention interval: it... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372056 Tue, 16 Mar 2010 15:19:49 +0100 3372056 http://www.medworm.com/index.php?rid=3372055&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1418%3Frss%3D1 To examine the neural basis of sequence learning, a fundamental but poorly understood human ability, we recorded event-related potentials (ERPs) while subjects viewed and memorized randomly directed sequences of motions for later imitation. Previously, we found that the amplitude of ERPs elicited by successive motion segments decreased as a function of each segment's serial position. This happened when subjects were required to remember the sequence, but not when they were performing a perceptual task. Here, to study the functional significance of this amplitude gradient in sequence learning, we presented each sequence several times in succession and examined changes in ERP amplitude as subjects learned the sequence through repeated observation and imitation. Behaviorally, with each repeti... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372055 Tue, 16 Mar 2010 15:19:49 +0100 3372055 http://www.medworm.com/index.php?rid=3372054&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1410%3Frss%3D1 Prolonged exposure to complex stimuli, such as faces, biases perceptual decisions toward nonadapted, dissimilar stimuli, leading to contrastive aftereffects. Here we tested the neural correlates of this perceptual bias using a functional magnetic resonance imaging adaptation (fMRIa) paradigm. Adaptation to a face or hand stimulus led to aftereffects by biasing the categorization of subsequent ambiguous face/hand composite stimuli away from the adaptor category. The simultaneously observed fMRIa in the face-sensitive fusiform face area (FFA) and in the body-part–sensitive extrastriate body area (EBA) depended on the behavioral response of the subjects: adaptation to the preferred stimulus of the given area led to larger signal reduction during trials when it biased perception than dur... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372054 Tue, 16 Mar 2010 15:19:49 +0100 3372054 http://www.medworm.com/index.php?rid=3372053&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1397%3Frss%3D1 The central cholinergic system regulates both the circadian clock and sleep-wake cycle and may participate in the feedback control of vigilance states on neural excitability in the suprachiasmatic nucleus (SCN) that houses the circadian clock. Here we investigate the mechanisms for cholinergic modulation of SCN neuron excitability. Cell-attached recordings indicate that the nonspecific cholinergic agonist carbachol (CCh) inhibited 55% and excited 21% SCN neurons, leaving 24% nonresponsive. Similar response proportions were produced by two muscarinic receptor [muscarinic acetylcholine receptor (mAChR)] agonists, muscarine and McN-A-343 (M1/4 agonist), but not by two nicotinic receptor (nAChR) agonists, nicotine and choline (7-nAChR agonist), which, however, produced similar response proport... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372053 Tue, 16 Mar 2010 15:19:49 +0100 3372053 http://www.medworm.com/index.php?rid=3372052&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1385%3Frss%3D1 Cutaneous myelinated nociceptors are known to exhibit considerable heterogeneity in their response to noxious heat. In the present experiments, we studied heat sensitivity among myelinated nociceptors during early postnatal life to determine whether this heterogeneity is correlated with other physiological and anatomical properties. A total of 129 cutaneous myelinated nociceptors were recorded intracellularly and characterized using mechanical and thermal skin stimuli in ex vivo preparations from neonatal Swiss–Webster (SW) mice across postnatal ages P2–P10; physiologically identified cells were iontophoretically labeled with neurobiotin for analyses of dorsal horn terminations from heat-sensitive and heat-insensitive cells. Our results show that heat sensitivity is not strictl... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372052 Tue, 16 Mar 2010 15:19:49 +0100 3372052 http://www.medworm.com/index.php?rid=3372051&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1375%3Frss%3D1 The terminal nerve (TN)-gonadotropin-releasing hormone (GnRH) neurons have been suggested to function as a neuromodulatory system that regulates the motivational and arousal state of the animal and have served as a model system for the study of GnRH neuron physiology. To investigate the synaptic control of the TN-GnRH neurons, we analyzed electrophysiologically the effect of GABA on the TN-GnRH neurons. GABA generally hyperpolarizes most of the neurons in the adult brain by activating GABAA receptors while the activation of GABAA receptors depolarizes some specific neurons in the mature brain. Here we examined the GABAA receptor-mediated responses in the TN-GnRH neurons of adult teleost fish, the dwarf gourami, by means of gramicidin-perforated patch-clamp and cell-attached patch-clamp rec... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372051 Tue, 16 Mar 2010 15:19:49 +0100 3372051 http://www.medworm.com/index.php?rid=3372050&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1357%3Frss%3D1 Trains of action potentials of rat and cat retinal ganglion cells (RGCs) were recorded intracellularly across a temperature range of 7–37°C. Phase plots of the experimental impulse trains were precision fit using multicompartment simulations of anatomically reconstructed rat and cat RGCs. Action potential excitation was simulated with a "Five-channel model" [Na, K(delayed rectifier), Ca, K(A), and K(Ca-activated) channels] and the nonspace-clamped condition of the whole cell recording was exploited to determine the channels' distribution on the dendrites, soma, and proximal axon. At each temperature, optimal phase-plot fits for RGCs occurred with the same unique channel distribution. The "waveform" of the electrotonic current was found to be temperature dependent, which reflected... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372050 Tue, 16 Mar 2010 15:19:49 +0100 3372050 http://www.medworm.com/index.php?rid=3372049&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1350%3Frss%3D1 The corticospinal pathway is the major pathway controlling human voluntary movements. After strong voluntary contractions, the efficacy of corticospinal transmission to elbow flexors is reduced for ~90 s, and this limits motoneuronal output. This reduction may reflect activity-dependent changes at cortico-motoneuronal synapses. We investigated whether similar changes occur in a leg muscle, tibialis anterior (TA). Electrical stimuli over high thoracic vertebrae activated corticospinal axons to evoke an EMG response in TA (TMEP). Stimuli were delivered before and after short 10-s and prolonged 1-min maximal contractions (MVCs) of ankle dorsiflexors. In two studies, stimuli were given with the muscle relaxed. In other studies, stimuli were given during weak contraction. After a 10-s MVC (stud... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372049 Tue, 16 Mar 2010 15:19:49 +0100 3372049 http://www.medworm.com/index.php?rid=3372048&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1337%3Frss%3D1 Regulation of the putative amiloride and benzamil (Bz)-insensitive TRPV1t salt taste receptor by phosphatidylinositol 4,5-bisphosphate (PIP2) was studied by monitoring chorda tympani (CT) taste nerve responses to 0.1 M NaCl solutions containing Bz (5 x 10–6 M; a specific ENaC blocker) and resiniferatoxin (RTX; 0–10 x 10–6 M; a specific TRPV1 agonist) in Sprague-Dawley rats and in wildtype (WT) and TRPV1 knockout (KO) mice. In rats and WT mice, RTX elicited a biphasic effect on the NaCl + Bz CT response, increasing the CT response between 0.25 x 10–6 and 1 x 10–6 M. At concentrations >1 x 10–6 M, RTX inhibited the CT response. An increase in PIP2 by topical lingual application of U73122 (a phospholipase C blocker) or diC8-PIP2 (a short chain synthetic ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372048 Tue, 16 Mar 2010 15:19:48 +0100 3372048 http://www.medworm.com/index.php?rid=3372047&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1329%3Frss%3D1 Pavlovian eyeblink conditioning is a useful experimental model for studying adaptive timing, an important aspect of skilled movements. The conditioned response (CR) is precisely timed to occur just before the onset of the expected unconditioned stimulus (US). The timing can be changed immediately, however, by varying parameters of the conditioned stimulus (CS). It has previously been shown that increasing the intensity of a peripheral CS or the frequency of a CS consisting of a train of stimuli to the mossy fibers shortens the latency of the CR. The adaptive timing of behavioral CRs probably reflects the timing of an underlying learned inhibitory response in cerebellar Purkinje cells. It is not known how the latency of this Purkinje cell CR is controlled. We have recorded form Purkinje cel... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372047 Tue, 16 Mar 2010 15:19:48 +0100 3372047 http://www.medworm.com/index.php?rid=3372046&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1322%3Frss%3D1 Nitric oxide (NO) has been recognized as an atypical neuronal messenger affecting synaptic transmission, but its cellular source has remained unresolved as the neuronal NO synthase isoform (nNOS) in brain areas such as the neocortex is expressed only by a small subset of inhibitory neurons. The involvement of the glial NOS isoform (iNOS) in modulating neuronal activity has been largely ignored because it has been accepted that this enzyme is regulated by gene induction following detrimental stimuli. Using acute brain slices from mouse neocortex and electrophysiology, we found that selective inhibition of iNOS reduced both spontaneous and evoked synaptic release. Moreover, iNOS inhibition partially prevented and reversed the potentiation of excitatory synapses in layer 2/3 pyramidal neurons... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372046 Tue, 16 Mar 2010 15:19:48 +0100 3372046 http://www.medworm.com/index.php?rid=3372045&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1315%3Frss%3D1 The genioglossus (GG) is considered the principle protrudor muscle of the human tongue. Unlike most skeletal muscles, GG electromyographic (EMG) activities are robustly preserved in sleep and thus may fulfill a critical role in preserving airway patency. Previous studies in human subjects also confirm that the GG EMG increases in response to chemoreceptor and mechanoreceptor stimulation. This increase occurs secondary to the recruitment of previously inactive motor units (MUs) and/or an increase in firing rate of already active MUs. Which strategy the nervous system uses when the synaptic drive onto GG motoneurons increases is not known. Here we report on GG whole muscle and tonic MU activities under conditions that mimic sleep, i.e., mild-moderate elevations in CO2 (3% inspired CO2 or the... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372045 Tue, 16 Mar 2010 15:19:48 +0100 3372045 http://www.medworm.com/index.php?rid=3372044&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1304%3Frss%3D1 This study provides evidence that plantar cutaneous afferents remarkably influence the soleus H-reflex and TA flexion reflex modulation patterns during stepping and support that actions of plantar cutaneous afferents onto spinal interneuronal circuits engaged in locomotion are manifested in a phase-dependent manner in chronic SCI subjects. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372044 Tue, 16 Mar 2010 15:19:48 +0100 3372044 http://www.medworm.com/index.php?rid=3372043&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1295%3Frss%3D1 Recruitment and repetitive firing of spinal motoneurons depend on the activation of persistent inward calcium and sodium currents (PICs) that are in turn facilitated by serotonin and norepinephrine that arise primarily from the brain stem. Considering that in rats motoneuron PICs are greatly facilitated by increasing the presynaptic release of norepinephrine with amphetamine, we sought similar evidence for the modulation of PICs in human motoneurons. Pairs of motor units were recorded during a gradually increasing and then decreasing voluntary contraction. The firing frequency (F) of the lower-threshold (control) motor unit was used as an estimate of the synaptic input to the higher-threshold (test) motor unit. Generally, PICs are initiated during the recruitment of a motoneuron and subseq... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372043 Tue, 16 Mar 2010 15:19:48 +0100 3372043 http://www.medworm.com/index.php?rid=3372042&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1283%3Frss%3D1 Activity-dependent alterations of synaptic transmission important for learning and memory are often induced by Ca2+ signals generated by depolarization. While it is widely assumed that Ca2+ is the essential transducer of depolarization into cellular plasticity, little effort has been made to test whether Ca2+-independent responses to depolarization might also induce memory-like alterations. It was recently discovered that peripheral axons of nociceptive sensory neurons in Aplysia display long-lasting hyperexcitability triggered by conditioning depolarization in the absence of Ca2+ entry (using nominally Ca2+-free solutions containing EGTA, "0Ca/EGTA") or the absence of detectable Ca2+ transients (adding BAPTA-AM, "0Ca/EGTA/BAPTA-AM"). The current study reports that depolarization of centra... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372042 Tue, 16 Mar 2010 15:19:48 +0100 3372042 http://www.medworm.com/index.php?rid=3372041&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1275%3Frss%3D1 Several recent studies have shown that extracting pattern motion direction is a dynamical process where edge motion is first extracted and pattern-related information is encoded with a small time lag by MT neurons. A similar dynamics was found for human reflexive or voluntary tracking. Here, we bring an essential, but still missing, piece of information by documenting macaque ocular following responses to gratings, unikinetic plaids, and barber-poles. We found that ocular tracking was always initiated first in the grating motion direction with ultra-short latencies (~55 ms). A second component was driven only 10–15 ms later, rotating tracking toward pattern motion direction. At the end the open-loop period, tracking direction was aligned with pattern motion direction (plaids) or the ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372041 Tue, 16 Mar 2010 15:19:48 +0100 3372041 http://www.medworm.com/index.php?rid=3372040&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1262%3Frss%3D1 Plantar flexor series elasticity can be used to dissociate muscle–fascicle and muscle–tendon behavior and thus afferent feedback during human walking. We used electromyography (EMG) and high-speed ultrasonography concomitantly to monitor muscle activity and muscle fascicle behavior in 19 healthy volunteers as they walked across a platform. On random trials, the platform was dropped (8 cm, 0.9 g acceleration) or held at a small inclination (up to ±3° in the parasagittal plane) with respect to level ground. Dropping the platform in the mid and late phases of stance produced a depression in the soleus muscle activity with an onset latency of about 50 ms. The reduction in ground reaction force also unloaded the plantar flexor muscles. The soleus muscle fascicles shortene... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372040 Tue, 16 Mar 2010 15:19:48 +0100 3372040 http://www.medworm.com/index.php?rid=3372039&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1253%3Frss%3D1 In the local cortical network, spontaneous emergent activity self-organizes in rhythmic patterns. These rhythms include a slow one (<1 Hz), consisting in alternation of up and down states, and also faster rhythms (10–80 Hz) generated during up states. Varying the temperature in the bath between 26 and 41°C resulted in a strong modulation of the emergent network activity. Up states became shorter for warmer temperatures and longer with cooling, whereas down states were shortest at physiological (36–37°C) temperature. The firing rate during up states was robustly modulated by temperature, increasing with higher temperatures. The sparse firing rate during down states hardly varied with temperature, thus resulting in a progressive merging of up and down states for temper... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372039 Tue, 16 Mar 2010 15:19:48 +0100 3372039 http://www.medworm.com/index.php?rid=3372038&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1238%3Frss%3D1 Generating sequences of multiple saccadic eye movements allows us to search our environment quickly and efficiently. Although the frontal eye field cortex (FEF) has been linked to target selection and making saccades, little is known about its role in the control and performance of the sequences of saccades made during self-guided visual search. We recorded from FEF cells while monkeys searched for a target embedded in natural scenes and examined the degree to which cells with visual and visuo-movement activity showed evidence of target selection for future saccades. We found that for about half of these cells, activity during the fixation period between saccades predicted the next saccade in a sequence at an early time that precluded selection based on current visual input to a cell's res... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372038 Tue, 16 Mar 2010 15:19:48 +0100 3372038 http://www.medworm.com/index.php?rid=3372037&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1226%3Frss%3D1 We report evidence of mode-locking to the envelope of a periodic stimulus in chopper units of the ventral cochlear nucleus (VCN). Mode-locking is a generalized description of how responses in periodically forced nonlinear systems can be closely linked to the input envelope, while showing temporal patterns of higher order than seen during pure phase-locking. Re-analyzing a previously unpublished dataset in response to amplitude modulated tones, we find that of 55% of cells (6/11) demonstrated stochastic mode-locking in response to sinusoidally amplitude modulated (SAM) pure tones at 50% modulation depth. At 100% modulation depth SAM, most units (3/4) showed mode-locking. We use interspike interval (ISI) scattergrams to unravel the temporal structure present in chopper mode-locked responses.... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372037 Tue, 16 Mar 2010 15:19:48 +0100 3372037 http://www.medworm.com/index.php?rid=3372036&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1209%3Frss%3D1 The role of auditory cortex in sound localization and its recalibration by experience was explored by measuring the accuracy with which ferrets turned toward and approached the source of broadband sounds in the horizontal plane. In one group, large bilateral lesions were made of the middle ectosylvian gyrus, where the primary auditory cortical fields are located, and part of the anterior and/or posterior ectosylvian gyrus, which contain higher-level fields. In the second group, the lesions were intended to be confined to primary auditory cortex (A1). The ability of the animals to localize noise bursts of different duration and level was measured before and after the lesions were made. A1 lesions produced a modest disruption of approach-to-target responses to short-duration stimuli (<500... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372036 Tue, 16 Mar 2010 15:19:48 +0100 3372036 http://www.medworm.com/index.php?rid=3372035&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1195%3Frss%3D1 The functional organization giving rise to stimulus selectivity in higher-order auditory neurons remains under active study. We explored the selectivity for motifs, spectrotemporally distinct perceptual units in starling song, recording the responses of 96 caudomedial mesopallium (CMM) neurons in European starlings (Sturnus vulgaris) under awake-restrained and urethane-anesthetized conditions. A subset of neurons was highly selective between motifs. Selectivity was correlated with low spontaneous firing rates and high spike timing precision, and all but one of the selective neurons had similar spike waveforms. Neurons were further tested with stimuli in which the notes comprising the motifs were manipulated. Responses to most of the isolated notes were similar in amplitude, duration, and t... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372035 Tue, 16 Mar 2010 15:19:48 +0100 3372035 http://www.medworm.com/index.php?rid=3372034&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1179%3Frss%3D1 Our ability to make rapid decisions based on sensory information belies the complexity of the underlying computations. Recently, "accumulator" models of decision making have been shown to explain the activity of parietal neurons as macaques make judgments concerning visual motion. Unraveling the operation of a decision-making circuit, however, involves understanding both the responses of individual components in the neural circuitry and the relationships between them. In this functional magnetic resonance imaging study of the decision process in humans, we demonstrate that an accumulator model predicts responses to visual motion in the intraparietal sulcus (IPS). Significantly, the metrics used to define responses within the IPS also reveal distinct but interacting nodes in a circuit, incl... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372034 Tue, 16 Mar 2010 15:19:48 +0100 3372034 http://www.medworm.com/index.php?rid=3372033&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1171%3Frss%3D1 The visually driven responses of macaque area V4 neurons are modulated during the preparation of saccadic eye movements, but the relationship between presaccadic modulation in area V4 and saccade preparation is poorly understood. Recent neurophysiological studies suggest that the variability across trials of spiking responses provides a more reliable signature of motor preparation than mean firing rate across trials. We compared the dynamics of the response rate and the variability in the rate across trials for area V4 neurons during the preparation of visually guided saccades. As in previous reports, we found that the mean firing rate of V4 neurons was enhanced when saccades were prepared to stimuli within a neuron's receptive field (RF) in comparison with saccades to a non-RF location. F... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372033 Tue, 16 Mar 2010 15:19:48 +0100 3372033 http://www.medworm.com/index.php?rid=3372032&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1158%3Frss%3D1 Prediction about outcomes constitutes a basic mechanism underlying informed economic decision making. A stimulus constitutes a reward predictor when it provides more information about the reward than the environmental background. Reward prediction can be manipulated in two ways, by varying the reward paired with the stimulus, as done traditionally in neurophysiological studies, and by varying the background reward while holding stimulus-reward pairing constant. Neuronal mechanisms involved in reward prediction should also be sensitive to changes in background reward independently of stimulus-reward pairing. We tested this assumption on a major brain structure involved in reward processing, the central and basolateral amygdala. In a 2 x 2 design, we examined the influence of rewarded and un... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372032 Tue, 16 Mar 2010 15:19:48 +0100 3372032 http://www.medworm.com/index.php?rid=3372031&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F3%2F1147%3Frss%3D1 Neocortex network activity varies from a desynchronized or activated state typical of arousal to a synchronized or deactivated state typical of quiescence. Such changes are usually attributed to the effects of neuromodulators released in the neocortex by nonspecific activating systems originating in basal forebrain and brain stem reticular formation. As a result, the only role attributed to thalamocortical cells projecting to primary sensory areas, such as barrel cortex, is to transmit sensory information. However, thalamocortical cells can undergo significant changes in spontaneous tonic firing as a function of state, although the role of such variations is unknown. Here we show that the tonic firing level of thalamocortical cells, produced by cholinergic and noradrenergic stimulation of ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3372031 Tue, 16 Mar 2010 15:19:48 +0100 3372031 http://www.medworm.com/index.php?rid=3245584&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Ffull%2F103%2F2%2F1146%3Frss%3D1 (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245584 Fri, 05 Feb 2010 22:37:01 +0100 3245584 http://www.medworm.com/index.php?rid=3245583&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Ffull%2F103%2F2%2F1145%3Frss%3D1 (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245583 Fri, 05 Feb 2010 22:37:01 +0100 3245583 http://www.medworm.com/index.php?rid=3245582&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1130%3Frss%3D1 Measuring variations of intracellular free calcium concentration through the changes in fluorescence of a calcium-sensitive dye is a ubiquitous technique in neuroscience. Despite its popularity, confidence intervals (CIs) on the estimated parameters of calcium dynamics models are seldom given. To address this issue, we have developed a two-stage model for ratiometric measurements obtained with a charge-coupled device (CCD) camera. Its first element embeds a parametric calcium dynamics model into a fluorescence intensity model and its second element probabilistically describes the fluorescence measurements by a CCD camera. Using Monte Carlo simulations, we first show that the classical ratiometric transformation gives reliable CIs for time constants only and not baseline calcium concentrati... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245582 Fri, 05 Feb 2010 22:37:01 +0100 3245582 http://www.medworm.com/index.php?rid=3245581&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1123%3Frss%3D1 Endocannabinoids are lipid derivatives that mediate paracrine and juxtacrine signaling between cells. In the hippocampal CA1 region, a retrograde endocannabinoid signal suppresses GABA release by acting on presynaptic cannabinoid receptor-1 (CB1) and can be functionally manifested as depolarization-induced suppression of inhibition (DSI). In the present study, whole cell patch-clamp recordings in hippocampal slices were made to examine DSI in rats from P7–P21. Robust DSI develops in rat hippocampus at postnatal ages greater than two weeks, but only modest DSI is observed in P7-9 rat. DSI in neonatal rats can be enhanced by activation of group I metabotropic glutamate receptors (mGluRs) or muscarinic acetylcholine receptors in those neonatal rats. The DSI is also enhanced by sustained... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245581 Fri, 05 Feb 2010 22:37:01 +0100 3245581 http://www.medworm.com/index.php?rid=3245580&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1114%3Frss%3D1 Odorants inhibit as well as excite olfactory receptor neurons (ORNs) in many species of animals. Cyclic nucleotide-dependent activation of canonical mammalian ORNs is well established but it is still unclear how odorants inhibit these cells. Here we further implicate phosphoinositide-3-kinase (PI3K), an indispensable element of PI signaling in many cellular processes, in olfactory transduction in rodent ORNs. We show that odorants rapidly and transiently activate PI3K in the olfactory cilia and in the olfactory epithelium in vitro. We implicate known G-protein–coupled isoforms of PI3K and show that they modulate not only the magnitude but also the onset kinetics of the electrophysiological response of ORNs to complex odorants. Finally, we show that the ability of a single odorant to ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245580 Fri, 05 Feb 2010 22:37:01 +0100 3245580 http://www.medworm.com/index.php?rid=3245579&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1104%3Frss%3D1 Cardiovascular and behavioral responses to circulating angiotensin require intact connectivity along the upper lamina terminalis joining the subfornical organ (SFO) with the median preoptic nucleus (MnPO). In the present study on MnPO neurons, we used whole cell patch-clamp recording techniques in brain slice preparations to evaluate the influence of metabotropic glutamate receptor (mGluR) agonists on modulating their intrinsic excitability and SFO-evoked glutamatergic and GABAergic postsynaptic currents. In 22/36 cells, bath application of a mGluR group I agonist (S)-3,5-dihydroxyphenylglycine (DHPG) induced a TTX-resistant inward current coupled with decrease in a membrane K+ conductance but also a possible increase in a nonselective cationic conductance. By contrast, 27/49 cells respond... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245579 Fri, 05 Feb 2010 22:37:01 +0100 3245579 http://www.medworm.com/index.php?rid=3245578&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1093%3Frss%3D1 Rectification of EMG signals is a common processing step used when performing electroencephalographic–electromyographic (EEG–EMG) coherence and EMG–EMG coherence. It is well known, however, that EMG rectification alters the power spectrum of the recorded EMG signal (interference EMG). The purpose of this study was to determine whether rectification of the EMG signal influences the capability of capturing the oscillatory input to a single EMG signal and the common oscillations between two EMG signals. Several EMG signals were reconstructed from experimentally recorded EMG signals from the surface of the first dorsal interosseus muscle and were manipulated to have an oscillatory input or common input (for pairs of reconstructed EMG signals) at various frequency bands (in Hz... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245578 Fri, 05 Feb 2010 22:37:01 +0100 3245578 http://www.medworm.com/index.php?rid=3245577&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1080%3Frss%3D1 It is known that after spinalization animals lose their ability to maintain lateral stability when standing or walking. A likely reason for this is a reduction of the postural limb reflexes (PLRs) driven by stretch and load receptors of the limbs. The aim of this study was to clarify whether spinal networks contribute to the generation of PLRs. For this purpose, first, PLRs were recorded in decerebrated rabbits before and after spinalization at T12. Second, the effects of epidural electrical stimulation (EES) at L7 on the limb reflexes were studied after spinalization. To evoke PLRs, the vertebrate column of the rabbit was fixed, whereas the hindlimbs were positioned on the platform. Periodic lateral tilts of the platform caused antiphase flexion–extension limbs movements, similar to... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245577 Fri, 05 Feb 2010 22:37:01 +0100 3245577 http://www.medworm.com/index.php?rid=3245576&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1066%3Frss%3D1 To investigate vestibuloocular reflex (VOR) adaptation produced by changes in peripheral vestibular afference, we developed and tested a vestibular "prosthesis" that senses yaw-axis angular head velocity and uses this information to modulate the rate of electrical pulses applied to the lateral canal ampullary nerve. The ability of the brain to adapt the different components of the VOR (gain, phase, axis, and symmetry) during chronic prosthetic electrical stimulation was studied in two squirrel monkeys. After characterizing the normal yaw-axis VOR, electrodes were implanted in both lateral canals and the canals were plugged. The VOR in the canal-plugged/instrumented state was measured and then unilateral stimulation was applied by the prosthesis. The VOR was repeatedly measured over several... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245576 Fri, 05 Feb 2010 22:37:01 +0100 3245576 http://www.medworm.com/index.php?rid=3245575&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1057%3Frss%3D1 The ability to notice relevant visual information has been assumed to be determined both by the relative salience of relevant information compared with distracters within a given display and by voluntary allocation of attention toward intended goals. A dominance of either of these two mechanisms in stimulus processing has been claimed by different theories. A central question in this context is to what degree and how task irrelevant signals can influence processing of target information. In the present study, participants had to detect a luminance change in various conditions among others against an irrelevant orientation change. The saliency of the latter was systematically varied and was found to be predictive for the proportion of detected information when relevant and irrelevant inform... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245575 Fri, 05 Feb 2010 22:37:01 +0100 3245575 http://www.medworm.com/index.php?rid=3245574&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1048%3Frss%3D1 This study seeks to determine whether mechanical filtering from conversion of lower-limb muscle activity to body sway, during standing balance, can be used to attenuate sway while maintaining biphasic lower-limb muscle responses using frequency-limited stochastic vestibular stimulation (SVS). We hypothesized that SVS deprived of frequencies <2 Hz would evoke biphasic muscle responses with minimal whole-body sway due to mechanical filtering of the higher-frequency muscle responses. Subjects were exposed to five stimulus bandwidths: two meant to induce sway responses (0–1 and 0–2 Hz) and three to dissociate vestibular-evoked muscle responses from whole-body sway (0–25, 1–25, and 2–25 Hz). Two main results emerged: 1) SVS-related sway was attenuated when frequ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245574 Fri, 05 Feb 2010 22:37:01 +0100 3245574 http://www.medworm.com/index.php?rid=3245573&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1036%3Frss%3D1 Risk and ambiguity are two conditions in which the consequences of possible outcomes are not certain. Under risk, the probabilities of different outcomes can be estimated, whereas under ambiguity, even these probabilities are not known. Although most people exhibit at least some aversion to both risk and ambiguity, the degree of these aversions is largely uncorrelated across subjects, suggesting that risk aversion and ambiguity aversion are distinct phenomena. Previous studies have shown differences in brain activations for risky and ambiguous choices and have identified neural mechanisms that may mediate transitions from conditions of ambiguity to conditions of risk. Unknown, however, is whether the value of risky and ambiguous options is necessarily represented by two distinct systems or... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245573 Fri, 05 Feb 2010 22:37:01 +0100 3245573 http://www.medworm.com/index.php?rid=3245572&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1020%3Frss%3D1 In this study, we examined whether this phenomenon is 1) dependent on a visual fixation reference, 2) selective for frequency bands (high-pass and low-pass noise) related to specific auditory spatial channels, 3) matched by a shift in the perceived straight-ahead (PSA), and 4) accompanied by a spatial shift for visual and/or bimodal (visual and auditory) targets. Subjects were tested in a dark echo-attenuated chamber with their heads fixed facing a cylindrical screen, behind which a mobile speaker/LED presented targets across the frontal field. Subjects fixated alternating reference spots (0, ±20°) horizontally or vertically while either localizing targets or indicating PSA using a laser pointer. Results showed that the spatial shift induced by ocular eccentricity is 1) preserve... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245572 Fri, 05 Feb 2010 22:37:01 +0100 3245572 http://www.medworm.com/index.php?rid=3245571&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F1007%3Frss%3D1 Protein kinase A (PKA) has been reported to regulate synaptic β -aminobutyric acid type A (GABAA) receptor currents, but whether PKA regulates GABAA receptor peri- and extrasynaptic tonic currents is unknown. GABAA receptors containing 4 subunits are important in mediating tonic inhibition and exist as both 4β and 4β receptors in the brain. To mimic GABA-independent and GABA-dependent tonic currents, we transfected HEK 293T cells with 4β3 or 4β32L subunits and recorded spontaneous currents in the absence of applied GABA and steady-state currents in the presence of 1 µM GABA. Both 4β3 and 4β32L receptors displayed spontaneous currents, but PKA activation increased spontaneous 4β3 currents substantially more than spontaneous 4β32L currents. ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245571 Fri, 05 Feb 2010 22:37:01 +0100 3245571 http://www.medworm.com/index.php?rid=3245570&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F986%3Frss%3D1 We tested the hypothesis that area 5 of the posterior parietal cortex (PPC) contributes to the planning of visually guided gait modifications. We recorded 121 neurons from the PPC of two cats during a task in which cats needed to process visual input to step over obstacles attached to a moving treadmill belt. During unobstructed locomotion, 64/121 (53%) of cells showed rhythmic activity. During steps over the obstacles, 102/121 (84%) of cells showed a significant change of their activity. Of these, 46/102 were unmodulated during the control task. We divided the 102 task-related cells into two groups on the basis of their discharge when the limb contralateral to the recording site was the first to pass over the obstacle. One group (41/102) was characterized by a brief, phasic discharge as t... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245570 Fri, 05 Feb 2010 22:37:00 +0100 3245570 http://www.medworm.com/index.php?rid=3245569&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F977%3Frss%3D1 Despite an age-related slowing in the contractile properties of the triceps surae, inherently low maximal motor unit firing rates (MUFRs) in the soleus are unchanged. Fatigue following high-intensity contractions is characterized by contractile slowing in conjunction with a reduction in MUFRs in young adults. Here we exploit the ageing model of the soleus to assess changes in neuromuscular function during fatigue and short-term recovery. We hypothesize that a high-intensity sustained contraction will cause minimal reductions in MUFRs in young and old subjects but that recovery of MUFRs will be delayed in aged subjects. We compared the effects of a high-intensity sustained task on the MUFRs of the soleus and triceps surae contractile properties in six young (~24 yr) and six old (~75 yr) men... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245569 Fri, 05 Feb 2010 22:37:00 +0100 3245569 http://www.medworm.com/index.php?rid=3245568&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F968%3Frss%3D1 This study examined the effects of changes in postural support on APAs using novel and familiar support paradigms. We also investigated whether postural strategies were refined with practice and how the CNS responded when multiple supports were available. Twelve healthy subjects stood on dual force platforms and performed 20 randomized left and right rapid leg-lift tasks in response to a visual cue under four conditions: unsupported, bilateral handgrip, bite plate, and a combined handgrip and bite plate condition. Vertical ground reaction forces, electromyography of limb, trunk and jaw muscles, and forces exerted on the support apparatus were recorded. Shift in center-of-pressure amplitude and duration were reduced with increased support. Muscles were recruited in advance of the focal move... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245568 Fri, 05 Feb 2010 22:37:00 +0100 3245568 http://www.medworm.com/index.php?rid=3245567&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F962%3Frss%3D1 In this study, we recorded STN activity in patients with Parkinson's disease during stimulation delivered through a clinical DBS electrode using standard therapeutic stimulus parameters. A microelectrode was used to record the firing of a single STN neuron during DBS (3–5 V, 80–200 Hz, 90- to 200-µs pulses; 33 neurons/11 patients). Firing rate was unchanged during the stimulus trains, and the recorded neurons did not show prolonged (s) changes in firing rate on termination of the stimulation. However, a brief (~1 ms), short-latency (6 ms) postpulse inhibition was seen in 10 of 14 neurons analyzed. A subset of neurons displayed altered firing patterns, with a predominant shift toward random firing. These data do not support the idea that DBS inactivates the STN and are ins... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245567 Fri, 05 Feb 2010 22:37:00 +0100 3245567 http://www.medworm.com/index.php?rid=3245566&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F950%3Frss%3D1 Control of tangential force plays a key role in everyday manipulations. In anesthetized monkeys, forces tangential to the skin were applied at a range of magnitudes comparable to those used in routine manipulations and in eight different directions. The paradigm used enabled separation of responses to tangential force from responses to the background normal force. For slowly adapting type I (SAI) afferents, tangential force responses ranged from excitatory through no response to suppression, with both a static and dynamic component. For fast adapting type I (FAI) afferents, responses were dynamic and excitatory only. Responses of both afferent types were scaled by tangential force magnitude, elucidating the neural basis for previous human psychophysical scaling data. Most afferents were di... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245566 Fri, 05 Feb 2010 22:37:00 +0100 3245566 http://www.medworm.com/index.php?rid=3245565&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F942%3Frss%3D1 The capacity to learn new motor sequences is fundamental to adaptive motor behavior. The early phase of motor sequence learning relies on the ventral and anterior striatal circuitry, whereas the late phase relies on the dorsal and posterior striatal circuitry. Early Parkinson's disease (PD) is mainly characterized by dopaminergic denervation of the dorsal and posterior striatum while sparing anterior and ventral regions. Dopaminergic medication improves dorsal and posterior striatum function by compensating for the loss of dopamine. However, previous work has shown that dopaminergic medication interferes with the ventral and anterior striatum function by overdosing this relatively intact structure in early-state PD. Here we test whether these effects are also observed over the time course ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245565 Fri, 05 Feb 2010 22:37:00 +0100 3245565 http://www.medworm.com/index.php?rid=3245564&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F934%3Frss%3D1 Precision and accuracy of the subjective visual vertical (SVV) modulate in the roll plane. At large roll angles, systematic SVV errors are biased toward the subject's body-longitudinal axis and SVV precision is decreased. To explain this, SVV models typically implement a bias signal, or a prior, in a head-fixed reference frame and assume the sensory input to be optimally tuned along the head-longitudinal axis. We tested the pattern of SVV adjustments both in terms of accuracy and precision in experiments in which the head and the trunk reference frames were not aligned. Twelve subjects were placed on a turntable with the head rolled about 28° counterclockwise relative to the trunk by lateral tilt of the neck to dissociate the orientation of head- and trunk-fixed sensors relative to gra... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245564 Fri, 05 Feb 2010 22:37:00 +0100 3245564 http://www.medworm.com/index.php?rid=3245563&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F924%3Frss%3D1 This study demonstrates the important role that light signals are encoded by both experiment of inhibitory receptors in IP cells. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245563 Fri, 05 Feb 2010 22:37:00 +0100 3245563 http://www.medworm.com/index.php?rid=3245562&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F915%3Frss%3D1 We examined the effects of repetitive stimulation of sensory afferents of the trigeminal tract on activity of NVsnpr neurons recorded extracellularly in vitro under physiologic [Ca2+]e (1.6 mM). Spontaneously active cells had either a tonic (n = 145) or a bursting (n = 46) firing pattern. Afferent stimulation altered burst duration and/or burst frequency in bursting cells and firing frequency in most tonic cells. In 28% of the latter, the firing pattern switched to rhythmic bursting. This effect could be mimicked by local application of N-methyl-d-aspartate and blocked by APV but not DNQX. Detailed analysis showed that rhythm indices (RIs) of 35 tonic neurons that were negative (nonrhythmic) before stimulation became significantly rhythmic (RI ≥ 0.01) after stimulation. Mean and median ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245562 Fri, 05 Feb 2010 22:37:00 +0100 3245562 http://www.medworm.com/index.php?rid=3245561&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F904%3Frss%3D1 Type A -aminobutyric acid (GABAA) receptors expressed in the dorsal motor nucleus of vagus (DMV) critically regulate the activity of vagal motor neurons and, by inference, the gastrointestinal (GI) tract. Two types of GABAA receptor-mediated inhibition have been identified in the brain, represented by phasic (Iphasic) and tonic (Itonic) inhibitory currents. The hypothesis that Itonic regulates neuron activity was tested in the DMV using whole cell patch-clamp recordings in transverse brain stem slices from rats. An Itonic was present in a subset of DMV neurons, which was determined to be mediated by different receptors than those mediating fast, synaptic currents. Preapplication of tetrodotoxin significantly decreased the resting Itonic amplitude in DMV neurons, suggesting that most of the... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245561 Fri, 05 Feb 2010 22:37:00 +0100 3245561 http://www.medworm.com/index.php?rid=3245560&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F887%3Frss%3D1 We report a distinct tradeoff in modulation sensitivity and tuning that is topographically ordered within the central nucleus of the inferior colliculus (CNIC). Spectrotemporal receptive fields (STRFs) were obtained with 16-channel electrodes inserted orthogonal to the isofrequency lamina. Surprisingly, temporal and spectral characteristics exhibited an opposing relationship along the tonotopic axis. For low best frequencies (BFs), units were selective for fast temporal and broad spectral modulations. A systematic progression was observed toward slower temporal and finer spectral modulation sensitivity at high BF. This tradeoff was strongly reflected in the arrangement of excitation and inhibition and, consequently, in the modulation tuning characteristics. Comparisons with auditory nerve ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245560 Fri, 05 Feb 2010 22:37:00 +0100 3245560 http://www.medworm.com/index.php?rid=3245559&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F875%3Frss%3D1 The lateral superior olive (LSO) is one of the earliest sites in the auditory pathway involved in processing acoustical cues to sound location. LSO neurons encode the interaural level difference (ILD) cue to azimuthal location. Here we investigated the effect of variations in the overall stimulus levels of sounds at the two ears on the sensitivity of LSO neurons to small differences in ILDs of pure tones. The neuronal firing rate versus ILD functions were found to depend greatly on the overall stimulus level, typically shifting along the ILD axis toward the excitatory ear and attaining greater maximal firing rates as stimulus level increased. Seventy-five percent of neurons showed significant shifts with changes in overall sound level. The range of ILDs corresponding to best neural acuity ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245559 Fri, 05 Feb 2010 22:37:00 +0100 3245559 http://www.medworm.com/index.php?rid=3245558&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F858%3Frss%3D1 Movement-related activity within the superior colliculus (SC) represents the desired displacement of an impending gaze shift. This representation must ultimately be transformed into position-based reference frames appropriate for coordinated eye–head gaze shifts. Parietal areas that project to the SC are modulated by the initial position of both the eye-re-head and head-re-body and SC activity is modulated by eye-re-head position. These considerations led us to investigate whether SC activity is modulated by the head-re-body position. We recorded activity from movement-related SC neurons while head-restrained monkeys performed a delayed-saccade task. Across blocks of trials, the horizontal position of the body was rotated under a space-fixed head to three to five different positions ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245558 Fri, 05 Feb 2010 22:37:00 +0100 3245558 http://www.medworm.com/index.php?rid=3245557&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F844%3Frss%3D1 Evidence suggests that the nervous system controls motor tasks using a low-dimensional modular organization of muscle activation. However, it is not clear if such an organization applies to coordination of human walking, nor how nervous system injury may alter the organization of motor modules and their biomechanical outputs. We first tested the hypothesis that muscle activation patterns during walking are produced through the variable activation of a small set of motor modules. In 20 healthy control subjects, EMG signals from eight leg muscles were measured across a range of walking speeds. Four motor modules identified through nonnegative matrix factorization were sufficient to account for variability of muscle activation from step to step and across speeds. Next, consistent with the cli... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245557 Fri, 05 Feb 2010 22:37:00 +0100 3245557 http://www.medworm.com/index.php?rid=3245556&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F827%3Frss%3D1 Previously, we introduced a monkey model for human frontal midline theta oscillations as a possible neural correlate of attention. It was based on homologous theta oscillations found in the monkey's prefrontal and anterior cingulate cortices (areas 9 and 32) in a self-initiated hand-movement task. However, it has not been confirmed whether theta activity in the monkey model consistently appears in other situations demanding attention. Here, we examined the detailed properties of theta oscillations in four variations of forewarned reaction time tasks with warning (S1) and imperative (S2) stimuli. We characterized the theta oscillations generated exclusively in areas 9 and 32, as follows: 1) in the S1-S2 interval where movement preparation and reward expectation were presumably involved, the... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245556 Fri, 05 Feb 2010 22:37:00 +0100 3245556 http://www.medworm.com/index.php?rid=3245555&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F817%3Frss%3D1 Multisensory neurons tuned to both vestibular and visual motion (optic flow) signals are found in several cortical areas in the dorsal visual stream. Here we examine whether such convergence occurs subcortically in the macaque thalamus. We searched the ventral posterior nuclei, including the anterior pulvinar, as well as the ventro-lateral and ventral posterior lateral nuclei, areas that receive vestibular signals from brain stem and deep cerebellar nuclei. Approximately a quarter of cells responded to three-dimensional (3D) translational and/or rotational motion. More than half of the responsive cells were convergent, thus responded during both rotation and translation. The preferred axes of translation/rotation were distributed throughout 3D space. The majority of the neurons were excite... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245555 Fri, 05 Feb 2010 22:37:00 +0100 3245555 http://www.medworm.com/index.php?rid=3245554&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F801%3Frss%3D1 The goal of this study was to determine whether the activity of neurons in the supplementary eye field (SEF) is sufficient to control saccade initiation in macaque monkeys performing a saccade countermanding (stop signal) task. As previously observed, many neurons in the SEF increase the discharge rate before saccade initiation. However, when saccades are canceled in response to a stop signal, effectively no neurons with presaccadic activity display discharge rate modulation early enough to contribute to saccade cancellation. Moreover, SEF neurons do not exhibit a specific threshold discharge rate that could trigger saccade initiation. Yet, we observed more subtle relations between SEF activation and saccade production. The activity of numerous SEF neurons was correlated with response time... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245554 Fri, 05 Feb 2010 22:37:00 +0100 3245554 http://www.medworm.com/index.php?rid=3245553&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F793%3Frss%3D1 We examined functional connectivity in isoflurane-anesthetized macaques to identify a network associated with posterior parahippocampal cortex (PPHC). Functional connectivity was observed between the PPHC and retrosplenial, posterior cingulate, superior temporal gyrus, and inferior parietal cortex. PPHC correlations were distinct from regions in parietal and temporal cortex activated by an oculomotor task. Comparison of macaque and human PPHC correlations revealed similarities that suggest the temporal-parietal region identified in the macaque may share a common lineage with human Brodmann area 39, a region thought to be involved in recollection. These results suggest that macaques and humans may have homologous PPHC-parietal pathways. By specifying the location of the putative macaque hom... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245553 Fri, 05 Feb 2010 22:37:00 +0100 3245553 http://www.medworm.com/index.php?rid=3245552&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F779%3Frss%3D1 Desert locusts (Schistocerca gregaria) can transform reversibly between the swarming gregarious phase and a solitarious phase, which avoids other locusts. This transformation entails dramatic changes in morphology, physiology, and behavior. We have used the lobula giant movement detector (LGMD) and its postsynaptic target, the descending contralateral movement detector (DCMD), which are visual interneurons that detect looming objects, to analyze how differences in the visual ecology of the two phases are served by altered neuronal function. Solitarious locusts had larger eyes and a greater degree of binocular overlap than those of gregarious locusts. The receptive field to looming stimuli had a large central region of nearly equal response spanning 120° x 60° in both phases. The DC... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245552 Fri, 05 Feb 2010 22:37:00 +0100 3245552 http://www.medworm.com/index.php?rid=3245551&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F761%3Frss%3D1 Spinal cord injury leads to severe problems involving impaired motor, sensory, and autonomic functions. After spinal injury there is an initial phase of hyporeflexia followed by hyperreflexia, often referred to as spasticity. Previous studies have suggested a relationship between the reappearance of endogenous plateau potentials in motor neurons and the development of spasticity after spinalization. To unravel the molecular mechanisms underlying the increased excitability of motor neurons and the return of plateau potentials below a spinal cord injury we investigated changes in gene expression in this cell population. We adopted a rat tail-spasticity model with a caudal spinal transection that causes a progressive development of spasticity from its onset after 2 to 3 wk until 2 mo postinju... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245551 Fri, 05 Feb 2010 22:37:00 +0100 3245551 http://www.medworm.com/index.php?rid=3245550&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F746%3Frss%3D1 Friction and gravity represent two basic physical constraints of terrestrial locomotion that affect both motor patterns and the biomechanics of bipedal gait. To provide insights into the spatiotemporal organization of the motor output in connection with ground contact forces, we studied adaptation of human gait to steady low-friction conditions. Subjects walked along a slippery walkway (7 m long; friction coefficient ~= 0.06) or a normal, nonslippery floor at a natural speed. We recorded gait kinematics, ground reaction forces, and bilateral electromyographic (EMG) activity of 16 leg and trunk muscles and we mapped the recorded EMG patterns onto the spinal cord in approximate rostrocaudal locations of the motoneuron (MN) pools to characterize the spatiotemporal organization of the motor ou... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245550 Fri, 05 Feb 2010 22:37:00 +0100 3245550 http://www.medworm.com/index.php?rid=3245549&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F733%3Frss%3D1 Cholinergic activation profoundly affects vertebrate forebrain networks, but pathway, cell type, and modality specificity remain poorly understood. Here we investigated cell-specific cholinergic modulation of neurons in the zebra finch forebrain song control nucleus HVC using in vitro whole cell recordings. The HVC contains projection neurons that exclusively project to either another song motor nucleus RA (robust nucleus of the arcopallium) (HVC-RAn) or the basal ganglia Area X (HVC-Xn) and these populations are synaptically coupled by a network of GABAergic interneurons. Among HVC-RAn, we observed two physiologically distinct classes that fire either phasically or tonically to injected current. Muscarine excited phasic HVC-RAn and most HVC-Xn. Effects were observed under conditions of bl... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245549 Fri, 05 Feb 2010 22:36:59 +0100 3245549 http://www.medworm.com/index.php?rid=3245548&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F725%3Frss%3D1 The massive transfer of information from the neocortex to the entorhinal cortex (and vice versa) is hindered by a powerful inhibitory control generated in the perirhinal cortex. In vivo and in vitro experiments performed in rodents and cats support this conclusion, further extended in the present study to the analysis of the interaction between the entorhinal cortex and other parahippocampal areas, such as the postrhinal and the retrosplenial cortices. The experiments were performed in the in vitro isolated guinea pig brain by a combined approach based on electrophysiological recordings and fast imaging of optical signals generated by voltage-sensitive dyes applied to the entire brain by arterial perfusion. Local stimuli delivered in different portions of the perirhinal, postrhinal, and re... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245548 Fri, 05 Feb 2010 22:36:59 +0100 3245548 http://www.medworm.com/index.php?rid=3245547&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F709%3Frss%3D1 Layer IV of the barrel cortex contains an anatomical map of the contralateral whisker pad, which serves as a useful reference in relating receptive field properties of cells to the cortical columns in which they reside. Recent studies have shown that the degree to which the surround receptive fields of layer IV cells are generated intracortically or subcortically depends on whether they lie in barrel or septal columns. To investigate whether this is true for layer V cells, we blocked intracortical activity in the barrel cortex by infusing muscimol from the cortical surface and measuring spike responses to sensory stimulation in the presence of locally iontophoresed bicuculline. Layer V cells beneath barrels had small subcortically generated single- or double-whisker center receptive fields... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245547 Fri, 05 Feb 2010 22:36:59 +0100 3245547 http://www.medworm.com/index.php?rid=3245546&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F698%3Frss%3D1 Various studies showed a clear impairment of cerebellar patients to modulate grip force in anticipation of the loads resulting from movements with a grasped object. This failure corroborated the theory of internal feedforward models in the cerebellum. Cerebellar damage also impairs the coordination of multiple-joint movements and this has been related to deficient prediction and compensation of movement-induced torques. To study the effects of disturbed torque control on feedforward grip-force control, two self-generated load conditions with different demands on torque control—one with movement-induced and the other with isometrically generated load changes—were directly compared in patients with cerebellar degeneration. Furthermore the cerebellum is thought to be more involved... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245546 Fri, 05 Feb 2010 22:36:59 +0100 3245546 http://www.medworm.com/index.php?rid=3245545&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F677%3Frss%3D1 The aim of the present study was to characterize the spatial and temporal features of synaptic and discharge receptive fields (RFs), and to quantify their relationships, in cat area 17. For this purpose, neurons were recorded intracellularly while high-frequency flashing bars were used to generate RFs maps for synaptic and spiking responses. Comparison of the maps shows that some features of the discharge RFs depended strongly on those of the synaptic RFs, whereas others were less dependent. Spiking RF duration depended poorly and spiking RF amplitude depended moderately on those of the underlying synaptic RFs. At the other extreme, the optimal spatial frequency and phase of the discharge RFs in simple cells were almost entirely inherited from those of the synaptic RFs. Subfield width, in ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245545 Fri, 05 Feb 2010 22:36:59 +0100 3245545 http://www.medworm.com/index.php?rid=3245544&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F667%3Frss%3D1 In hippocampus, synchronous activation of CA1 pyramidal neurons causes a rapid, extracellular, population alkaline transient (PAT). It has been suggested that the plasma membrane Ca2+-ATPase (PMCA) is the source of this alkalinization, because it exchanges cytosolic Ca2+ for external H+. Evidence supporting this hypothesis, however, has thus far been inconclusive. We addressed this long-standing problem by measuring surface alkaline transients (SATs) from voltage-clamped CA1 pyramidal neurons in juvenile mouse hippocampal slices, using concentric (high-speed, low-noise) pH microelectrodes placed against the somata. In saline containing benzolamide (a poorly permeant carbonic anhydrase blocker), a 2-s step from –60 to 0 mV caused a mean SAT of 0.02 unit pH. Addition of 5 mM HEPES to t... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245544 Fri, 05 Feb 2010 22:36:59 +0100 3245544 http://www.medworm.com/index.php?rid=3245543&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F659%3Frss%3D1 In this study, we recorded endplate currents over a wide range of extracellular Ca2+ concentrations and found the expected Ca2+ dependency of release. A graphical technique was used to estimate p (probability of release) and n using standard binomial assumptions. The results suggested n was Ca2+ dependent. The data were simulated using compound binomial statistics with variable n (Ca2+ dependent) or fixed n (Ca2+ independent). With fixed n, successful simulation of increasing Ca2+ required that p increase abruptly at some sites from very low to high values. Successful simulation with variable n required the introduction of previously silent release sites (p = 0) with high values of p. Thus the success of both simulations required abrupt, large increases of p at a subset of release sites wi... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245543 Fri, 05 Feb 2010 22:36:59 +0100 3245543 http://www.medworm.com/index.php?rid=3245542&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F648%3Frss%3D1 In this study, we examined the location of 5-HT2C-like receptors and determined whether endogenously released serotonin also initiates vocalizations by activating 5-HT2C-like receptors in male Xenopus brains. To this end, we first identified the specific location of 5-HT2C-like receptors using immunohistochemistry. We next examined which of the populations of neurons that express 5-HT2C-like receptors are functionally relevant for initiating fictive vocalizations by applying a 5-HT2C receptor agonist to brains transected at various levels. Of four populations of immunopositive neurons, we showed that 5-HT2C-like receptors located in two areas of the brain stem vocal circuit, the raphe nucleus and motor nucleus IX-X, initiate fictive vocalizations. We next showed that endogenous serotonin c... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245542 Fri, 05 Feb 2010 22:36:59 +0100 3245542 http://www.medworm.com/index.php?rid=3245541&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F641%3Frss%3D1 Based on kinematic properties and distinct substrates, there are different classes of eyelid movement described as eyeblinks. We investigate whether the eyelid movements made in response to a conditioned stimulus (CS) are a category of eyelid movements distinct from blinks. Human subjects received 60 trials of classical eyelid conditioning with a tone as the CS and electrical stimulation of the supraorbital branch of the trigeminal nerve as the unconditioned stimulus (UCS). Before and after training, reflex blinks were elicited with the UCS. The kinematics of conditioned responses (CRs) differed significantly from those of reflex blinks. The slope of the amplitude-maximum velocity function was steeper for reflex blinks than for CRs, and reflex blink duration was significantly shorter than ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245541 Fri, 05 Feb 2010 22:36:59 +0100 3245541 http://www.medworm.com/index.php?rid=3245540&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F632%3Frss%3D1 In this study, we were able to detect significant hybridization for Shal-related family members 1 and 2 (Kv4.1 and 4.2) within the SCN. In addition, we used Western blot to show that the Kv4.1 and 4.2 proteins are expressed in SCN tissue. We further show that the magnitude of the IA current exhibits a diurnal rhythm that peaks during the day in the dorsal region of the mouse SCN. This rhythm seems to be driven by a subset of SCN neurons with a larger peak current and a longer decay constant. Importantly, this rhythm in neurons in the dorsal SCN continues in constant darkness, providing an important demonstration of the circadian regulation of an intrinsic voltage-gated current in mammalian cells. We conclude that the anatomical expression, biophysical properties, and pharmacological profil... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245540 Fri, 05 Feb 2010 22:36:59 +0100 3245540 http://www.medworm.com/index.php?rid=3245539&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F623%3Frss%3D1 The present work investigated presynaptic modulation of Ia afferents in the extensor carpi radialis (ECR) when young and old adults exerted a wrist extension force either to support an inertial load (position control) or to achieve an equivalent constant torque against a rigid restraint (force control) at 5, 10, and 15% of the maximal force. H reflexes were evoked in the ECR by stimulating the radial nerve above the elbow. A conditioning stimulus was applied to the median nerve above the elbow to assess presynaptic inhibition of homonymous Ia afferents (D1 inhibition) or at the wrist (palmar branch) to assess the ongoing presynaptic inhibition of heteronymous Ia afferents that converge onto the ECR motor neuron pool (heteronymous Ia facilitation). The young adults had less D1 inhibition an... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245539 Fri, 05 Feb 2010 22:36:59 +0100 3245539 http://www.medworm.com/index.php?rid=3245538&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F616%3Frss%3D1 The hamstring reflex response has been suggested to play a substantial role in knee joint stabilization during anterior tibial translation. The present study was performed to determine which afferent pathways contribute to the hamstring reflex as well as the potential effects of specific afferent pathways on functional knee stability. Short- and medium-latency hamstring reflexes (SLR and MLR) were evoked by anterior tibial translation in 35 healthy subjects during standing with 30° knee flexion. Nerve cooling, tizanidine, and ischemia were employed to differentiate afferent pathways. Two hours of thigh cooling (n = 10) resulted in a significant increase in MLR latency and, to a lesser extent, SLR latency. No significant changes were recorded in reflex sizes or maximum tibial translatio... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245538 Fri, 05 Feb 2010 22:36:59 +0100 3245538 http://www.medworm.com/index.php?rid=3245537&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F2%2F603%3Frss%3D1 The performance of adaptive behavior relies on continuous sensory feedback to produce relevant modifications to central motor patterns. The femoral chordotonal organ (FeCO) of the legs of the desert locust monitors the movements of the tibia about the femoro-tibial joint. A ventral midline population of spiking local interneurons in the metathoracic ganglia integrates inputs from the FeCO. We used a Wiener kernel cross-correlation method combined with a Gaussian white noise stimulation of the FeCO to completely characterize and model the output dynamics of the ventral midline population of interneurons. A wide range of responses were observed, and interneurons could be classified into three broad groups that received excitatory and inhibitory or principally inhibitory or excitatory synapti... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3245537 Fri, 05 Feb 2010 22:36:59 +0100 3245537 http://www.medworm.com/index.php?rid=3161574&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F591%3Frss%3D1 A central theme of systems neuroscience is to characterize the tuning of neural responses to sensory stimuli or the production of movement. Statistically, we often want to estimate the parameters of the tuning curve, such as preferred direction, as well as the associated degree of uncertainty, characterized by error bars. Here we present a new sampling-based, Bayesian method that allows the estimation of tuning-curve parameters, the estimation of error bars, and hypothesis testing. This method also provides a useful way of visualizing which tuning curves are compatible with the recorded data. We demonstrate the utility of this approach using recordings of orientation and direction tuning in primary visual cortex, direction of motion tuning in primary motor cortex, and simulated data. (Sour... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161574 Tue, 12 Jan 2010 00:12:44 +0100 3161574 http://www.medworm.com/index.php?rid=3161573&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F573%3Frss%3D1 Spinal circuits may organize trajectories using pattern generators and synergies. In frogs, prior work supports fixed-duration pulses of fixed composition synergies, forming primitives. In wiping behaviors, spinal frogs adjust their motor activity according to the starting limb position and generate fairly straight and accurate isochronous trajectories across the workspace. To test whether a compact description using primitives modulated by proprioceptive feedback could reproduce such trajectory formation, we built a biomechanical model based on physiological data. We recorded from hindlimb muscle spindles to evaluate possible proprioceptive input. As movement was initiated, early skeletofusimotor activity enhanced many muscle spindles firing rates. Before movement began, a rapid estimate ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161573 Tue, 12 Jan 2010 00:12:44 +0100 3161573 http://www.medworm.com/index.php?rid=3161572&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F564%3Frss%3D1 Correlations between neural activity in primary motor cortex (M1) and arm kinematics have recently been shown to be temporally extensive and spatially complex. These results provide a sophisticated account of M1 processing and suggest that M1 neurons encode high-level movement trajectories, termed "pathlets." However, interpreting pathlets is difficult because the mapping between M1 activity and arm kinematics is indirect: M1 activity can generate movement only via spinal circuitry and the substantial complexities of the musculoskeletal system. We hypothesized that filter-like complexities of the musculoskeletal system are sufficient to generate temporally extensive and spatially complex correlations between motor commands and arm kinematics. To test this hypothesis, we extended the comput... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161572 Tue, 12 Jan 2010 00:12:43 +0100 3161572 http://www.medworm.com/index.php?rid=3161571&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F557%3Frss%3D1 A spatial/nonspatial functional dissociation between the dorsal and ventral visual pathways is well established and has formed the basis of domain-specific theories of prefrontal cortex (PFC). Inconsistencies in the literature regarding prefrontal organization, however, have led to questions regarding whether the nature of the dissociations observed in PFC during working memory are equivalent to those observed in the visual pathways for perception. In particular, the dissociation between dorsal and ventral PFC during working memory for locations versus object identities has been clearly present in some studies but not in others, seemingly in part due to the type of objects used. The current study compared functional MRI activation during delayed-recognition tasks for shape or color, two ob... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161571 Tue, 12 Jan 2010 00:12:43 +0100 3161571 http://www.medworm.com/index.php?rid=3161570&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F543%3Frss%3D1 Spatial updating is the ability to keep track of the position of world-fixed objects while we move. In the case of vision, this phenomenon is called spatial constancy and has been studied in head-restraint conditions. During head-restrained smooth pursuit, it has been shown that the saccadic system has access to extraretinal information from the pursuit system to update the objects' position in the surrounding environment. However, during head-unrestrained smooth pursuit, the saccadic system needs to keep track of three different motor commands: the ocular smooth pursuit command, the vestibuloocular reflex (VOR), and the head movement command. The question then arises whether saccades compensate for these movements. To address this question, we briefly presented a target during sinusoidal ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161570 Tue, 12 Jan 2010 00:12:43 +0100 3161570 http://www.medworm.com/index.php?rid=3161569&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F531%3Frss%3D1 Cochlear implants stimulate the auditory nerve with amplitude-modulated (AM) electric pulse trains. Pulse rates >2,000 pulses per second (pps) have been hypothesized to enhance transmission of temporal information. Recent studies, however, have shown that higher pulse rates impair phase locking to sinusoidal AM in the auditory cortex and impair perceptual modulation detection. Here, we investigated the effects of high pulse rates on the temporal acuity of transmission of pulse trains to the auditory cortex. In anesthetized guinea pigs, signal-detection analysis was used to measure the thresholds for detection of gaps in pulse trains at rates of 254, 1,017, and 4,069 pps and in acoustic noise. Gap-detection thresholds decreased by an order of magnitude with increases in pulse rate from 2... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161569 Tue, 12 Jan 2010 00:12:43 +0100 3161569 http://www.medworm.com/index.php?rid=3161568&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F519%3Frss%3D1 Several regions of the brain are involved in smooth-pursuit eye movement (SPEM) control, including the cortical areas MST (medial superior temporal) and FEF (frontal eye field). It has been shown that the eye-movement responses to a brief perturbation of the visual target during ongoing pursuit increases with higher pursuit velocities. To further investigate the underlying neuronal mechanism of this nonlinear dynamic gain control and the contributions of different cortical areas to it, we recorded from MSTd (dorsal division of the MST area) neurons in behaving monkeys (Macaca mulatta) during step-ramp SPEM (5–20°/s) with and without superimposed target perturbation (one cycle, 5 Hz, ±10°/s). Smooth-pursuit–related MSTd neurons started to increase their activity o... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161568 Tue, 12 Jan 2010 00:12:43 +0100 3161568 http://www.medworm.com/index.php?rid=3161567&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F511%3Frss%3D1 In human motor cortex transcranial magnetic stimulation (TMS) has been used to identify short-interval intracortical inhibition (SICI) corresponding to -aminobutyric acid type A (GABAA) effects and long-interval intracortical inhibition (LICI) and the cortical silent period (SP) corresponding to postsynaptic GABAB effects. Presynaptic GABAB effects, corresponding to disinhibition, can also be identified with TMS and have been shown to be acting during LICI by measuring SICI after a suprathreshold priming stimulus (PS). The duration of disinhibition is not certain and, guided by studies in experimental preparations, we hypothesized that it may be longer-lasting than postsynaptic inhibition, leading to a period of late cortical disinhibition and consequently a net increase in corticospinal e... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161567 Tue, 12 Jan 2010 00:12:43 +0100 3161567 http://www.medworm.com/index.php?rid=3161566&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F499%3Frss%3D1 It is estimated that ~1.5 million Americans suffer a traumatic brain injury (TBI) every year, of which ~80% are considered mild injuries. Because symptoms caused by mild TBI last less than half an hour by definition and apparently resolve without treatment, the study of mild TBI is often neglected resulting in a significant knowledge gap for this wide-spread problem. In this work, we studied functional (electrophysiological) alterations of the neonatal/juvenile hippocampus after experimental mild TBI. Our previous work reported significant cell death after in vitro injury >10% biaxial deformation. Here we report that biaxial deformation as low as 5% affected neuronal function during the first week after in vitro mild injury of hippocampal slice cultures. These results suggest that even ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161566 Tue, 12 Jan 2010 00:12:43 +0100 3161566 http://www.medworm.com/index.php?rid=3161564&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F490%3Frss%3D1 Spinal cord sympathetic preganglionic neurons (SPNs) integrate activity from descending and sensory systems to determine the final central output of the sympathetic nervous system. The intermediolateral column (IML) has the highest number and density of SPNs and, within this region, SPN somas are found in distinct clusters within thoracic and upper lumbar spinal segments. Whereas SPNs exhibit a rostrocaudal gradient of end-target projections, individual clusters contain SPNs with diverse functional roles. Here we explored diversity in the electrophysiological properties observed in Hb9-eGFP–identified SPNs in the IML of neonatal mice. Overall, mouse SPN intrinsic membrane properties were comparable with those seen in other species. A wide range of values was obtained for all measured... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161564 Tue, 12 Jan 2010 00:12:43 +0100 3161564 http://www.medworm.com/index.php?rid=3161563&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F479%3Frss%3D1 Activity-dependent changes in excitatory synaptic transmission in the CNS have been shown to depend on the regulation of -amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors (AMPARs). In particular, several lines of evidence suggest that reversible phosphorylation of AMPAR subunit glutamate receptor 1 (GluR1, also referred to as GluA1 or GluR-A) plays a role in long-term potentiation (LTP) and long-term depression (LTD). We previously reported that regulation of serines (S) 831 and 845 on the GluR1 subunit may play a critical role in bidirectional synaptic plasticity in the Schaffer collateral inputs to CA1. Specifically, gene knockin mice lacking both S831 and S845 phosphorylation sites ("double phosphomutants"), where both serine residues were replaced by alanines (A), showed a... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161563 Tue, 12 Jan 2010 00:12:43 +0100 3161563 http://www.medworm.com/index.php?rid=3161562&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F469%3Frss%3D1 We have demonstrated that 4-aminopyridine-3-methanol (4-AP-3-MeOH), a 4-aminopyridine derivative, significantly restores axonal conduction in stretched spinal cord white-matter strips and shows no preference in restoring large and small axons. This compound is 10 times more potent when compared with 4-AP and other derivatives in restoring axonal conduction. Unlike 4-AP, 4-AP-3-MeOH can restore axonal conduction without changing axonal electrophysiological properties. In addition, we also have confirmed that 4-AP-3-MeOH is indeed an effective blocker of IA based on patch-clamp studies using guinea pig dorsal root ganglia cells. Furthermore, we have also provided the critical evidence to confirm the unmasking of potassium channels following mechanical injury. Taken together, our data further... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161562 Tue, 12 Jan 2010 00:12:43 +0100 3161562 http://www.medworm.com/index.php?rid=3161561&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F458%3Frss%3D1 -Aminobutyric acid (GABA)–gated chloride channel receptors are abundant in the CNS, where their physiological role is to mediate fast inhibitory neurotransmission. In insects, this inhibitory transmission plays a crucial role in olfactory information processing. In an effort to understand the nature and properties of the ionotropic receptors involved in these processes in the honeybee Apis mellifera, we performed a pharmacological and molecular characterization of GABA-gated channels in the primary olfactory neuropile of the honeybee brain—the antennal lobe (AL)—using whole cell patch-clamp recordings coupled with single-cell RT-PCR. Application of GABA onto AL cells at –110 mV elicited fast inward currents, demonstrating the existence of ionotropic GABA-gated chlor... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161561 Tue, 12 Jan 2010 00:12:43 +0100 3161561 http://www.medworm.com/index.php?rid=3161560&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F446%3Frss%3D1 The precedence effect (PE) is an auditory spatial illusion whereby two identical sounds presented from two separate locations with a delay between them are perceived as a fused single sound source whose position depends on the value of the delay. By training cats using operant conditioning to look at sound sources, we have previously shown that cats experience the PE similarly to humans. For delays less than ±400 µs, cats exhibit summing localization, the perception of a "phantom" sound located between the sources. Consistent with localization dominance, for delays from 400 µs to ~10 ms, cats orient toward the leading source location only, with little influence of the lagging source. Finally, echo threshold was reached for delays >10 ms, where cats first began to orie... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161560 Tue, 12 Jan 2010 00:12:43 +0100 3161560 http://www.medworm.com/index.php?rid=3161559&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F441%3Frss%3D1 In this study, we examined whether KNa channels coupled to AMPA receptors are modulated by metabotropic glutamate receptors (mGluRs) in lamprey spinal cord neurons. Activation of mGluR1 strongly inhibited the AMPA-induced KNa current. However, when intracellular Ca2+ was chelated with 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA), the KNa current was enhanced by mGluR1. Activation of protein kinase C (PKC) mimicked the inhibitory effect of mGluR1 on the KNa current. Blockade of PKC prevented the mGluR1-induced inhibition of the KNa current, but did not affect the enhancement of the current seen in BAPTA. Together these results suggest that mGluR1 can differentially modulate AMPA-induced KNa current in a Ca2+- and PKC-dependent manner. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161559 Tue, 12 Jan 2010 00:12:43 +0100 3161559 http://www.medworm.com/index.php?rid=3161558&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F429%3Frss%3D1 Stretch reflexes contribute to arm impedance and longer-latency stretch reflexes exhibit increased sensitivity during interactions with compliant or unstable environments. This increased sensitivity is consistent with a regulation of arm impedance to compensate for decreased stability of the environment, but the specificity of this modulation has yet to be investigated. Many tasks, such as tool use, compromise arm stability along specific directions, and stretch reflexes tuned to those directions could present an efficient mechanism for regulating arm impedance in a task-appropriate manner. To be effective, such tuning should adapt not only to the mechanical properties of the environment but to those properties in relation to the arm, which also has directionally specific mechanical proper... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161558 Tue, 12 Jan 2010 00:12:43 +0100 3161558 http://www.medworm.com/index.php?rid=3161557&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F419%3Frss%3D1 Cone light responses are transmitted to postsynaptic neurons by changes in the rate of synaptic vesicle release. Vesicle pool size at the cone synapse constrains the amount of release and can thus shape contrast detection. We measured the number of vesicles in the rapidly releasable and reserve pools at cone ribbon synapses by performing simultaneous whole cell recording from cones and horizontal or off bipolar cells in the salamander retinal slice preparation. We found that properties of spontaneously occurring miniature excitatory postsynaptic currents (mEPSCs) are representative of mEPSCs evoked by depolarizing presynaptic stimulation. Strong, brief depolarization of the cone stimulated release of the entire rapidly releasable pool (RRP) of vesicles. Comparing charge transfer of the EPS... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161557 Tue, 12 Jan 2010 00:12:43 +0100 3161557 http://www.medworm.com/index.php?rid=3161556&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F409%3Frss%3D1 Systemic administration of µ-opioids at clinical doses for analgesia typically slows respiratory rate. Mu-opioid receptors (MORs) on pre-Bötzinger Complex (pre-BötC) respiratory neurons, the putative kernel of respiratory rhythmogenesis, are potential targets. The purpose of this study was to determine the contribution of pre-BötC MORs to the bradypnea produced in vivo by intravenous administration of clinically relevant infusion rates of remifentanil (remi), a short-acting, potent µ-opioid analgesic. In decerebrate dogs, multibarrel micropipettes were used to record pre-BötC neuronal activity and to eject the opioid antagonist naloxone (NAL, 0.5 mM), the glutamate agonist d-homocysteic acid (DLH, 20 mM), or the MOR agonist [d-Ala2, N-Me-Phe4, gly-ol5]-enkep... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161556 Tue, 12 Jan 2010 00:12:43 +0100 3161556 http://www.medworm.com/index.php?rid=3161555&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F402%3Frss%3D1 In conclusion, we showed a modulation of the grip force with moisture level and hypothesized novel mechanisms of moisture regulation that tend to stabilize the moisture level toward the value that minimizes grip force. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161555 Tue, 12 Jan 2010 00:12:43 +0100 3161555 http://www.medworm.com/index.php?rid=3161554&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F392%3Frss%3D1 We examined the effects of the phorbol ester PDBu, which has protein kinase C (PKC) dependent and independent actions on presynaptic transmitter release. PDBu increased phasic and asynchronous release in parallel. However, while PKC inhibition had relatively minor inhibitory effects on PDBu potentiation of phasic and total release during action potential trains, PKC inhibition strongly reduced phorbol-potentiated asynchrony, through actions most evident late during stimulus trains. These results lend new insight into PKC-dependent and -independent effects on transmitter release and suggest the possibility of differential control of synchronous versus asynchronous vesicle release. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161554 Tue, 12 Jan 2010 00:12:43 +0100 3161554 http://www.medworm.com/index.php?rid=3161553&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F382%3Frss%3D1 Recent studies suggest that reactive oxygen species (ROS) are functional messenger molecules in central sensitization, an underlying mechanism of persistent pain. Because spinal cord long-term potentiation (LTP) is the electrophysiological basis of central sensitization, this study investigates the effects of the increased or decreased spinal ROS levels on spinal cord LTP. Spinal cord LTP is induced by either brief, high-frequency stimulation (HFS) of a dorsal root at C-fiber intensity or superfusion of a ROS donor, tert-butyl hydroperoxide (t-BOOH), onto rat spinal cord slice preparations. Field excitatory postsynaptic potentials (fEPSPs) evoked by dorsal root stimulations with either Aβ- or C-fiber intensity are recorded from the superficial dorsal horn. HFS significantly increases ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161553 Tue, 12 Jan 2010 00:12:43 +0100 3161553 http://www.medworm.com/index.php?rid=3161551&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F371%3Frss%3D1 Cav2.1 channels regulate Ca2+ signaling and excitability of cerebellar Purkinje neurons. These channels undergo a dual feedback regulation by incoming Ca2+ ions, Ca2+-dependent facilitation and inactivation. Endogenous Ca2+-buffering proteins, such as parvalbumin (PV) and calbindin D-28k (CB), are highly expressed in Purkinje neurons and therefore may influence Cav2.1 regulation by Ca2+. To test this, we compared Cav2.1 properties in dissociated Purkinje neurons from wild-type (WT) mice and those lacking both PV and CB (PV/CB–/–). Unexpectedly, P-type currents in WT and PV/CB–/– neurons differed in a way that was inconsistent with a role of PV and CB in acute modulation of Ca2+ feedback to Cav2.1. Cav2.1 currents in PV/CB–/– neurons exhibited increased v... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161551 Tue, 12 Jan 2010 00:12:43 +0100 3161551 http://www.medworm.com/index.php?rid=3161550&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F360%3Frss%3D1 Neural substrates for processing constant speed visual motion have been extensively studied. Less is known about the brain activity patterns when the target speed changes continuously, for instance under the influence of gravity. Using functional MRI (fMRI), here we compared brain responses to accelerating/decelerating targets with the responses to constant speed targets. The target could move along the vertical under gravity (1g), under reversed gravity (–1g), or at constant speed (0g). In the first experiment, subjects observed targets moving in smooth motion and responded to a GO signal delivered at a random time after target arrival. As expected, we found that the timing of the motor responses did not depend significantly on the specific motion law. Therefore brain activity in th... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161550 Tue, 12 Jan 2010 00:12:42 +0100 3161550 http://www.medworm.com/index.php?rid=3161549&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F346%3Frss%3D1 Current anatomical models of the cortico–basal ganglia (BG) network predict reciprocal discharge patterns between the external and internal segments of the globus pallidus (GPe and GPi, respectively), as well as cortical driving of BG activity. However, physiological studies revealing similarity in the transient responses of GPe and GPi neurons cast doubts on these predictions. Here, we studied the discharge properties of GPe, GPi, and primary motor cortex neurons of two monkeys in two distinct states: when eyes are open versus when they are closed. Both pallidal populations exhibited decreased discharge rates in the "eye closed" state accompanied by elevated values of the coefficient of variation (CV) of their interspike interval (ISI) distributions. The pallidal modulations in disc... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161549 Tue, 12 Jan 2010 00:12:42 +0100 3161549 http://www.medworm.com/index.php?rid=3161548&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F334%3Frss%3D1 Electrical stimulation of the brain is a valuable research tool and has shown therapeutic promise in the development of new sensory neural prosthetics. Despite its widespread use, we still do not fully understand how current passed through a microelectrode interacts with functioning neural circuits. Past behavioral studies have suggested that weak electrical stimulation (referred to as microstimulation) of sensory areas of cortex produces percepts that are similar to those generated by normal sensory stimuli. In contrast, electrophysiological studies using in vitro or anesthetized preparations have shown that neural activity produced by brief microstimulation is radically different and longer lasting than normal responses. To help reconcile these two aspects of microstimulation, we examine... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161548 Tue, 12 Jan 2010 00:12:42 +0100 3161548 http://www.medworm.com/index.php?rid=3161547&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F322%3Frss%3D1 Topographic cortical representation of echo delay, the cue for target range, is an organizational feature implemented in the auditory cortices of certain bats dedicated to catch flying insects. Such cortical echo-delay maps provide a calibrated neural representation of object spatial distance. To assess general requirements for echo-delay computations, cortical delay sensitivity was examined in the short-tailed fruit bat Carollia perspicillata that uses frequency-modulated (FM) echolocation signals. Delay-tuned neurons with temporal specificity comparable to those of insectivorous bats are located within the high-frequency (HF) field of the auditory cortex. All recorded neurons in the HF field respond well to single pure-tone and FM-FM stimulus pairs. The neurons respond to identical FM ha... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161547 Tue, 12 Jan 2010 00:12:42 +0100 3161547 http://www.medworm.com/index.php?rid=3161546&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F297%3Frss%3D1 Resting state functional connectivity MRI (fcMRI) is widely used to investigate brain networks that exhibit correlated fluctuations. While fcMRI does not provide direct measurement of anatomic connectivity, accumulating evidence suggests it is sufficiently constrained by anatomy to allow the architecture of distinct brain systems to be characterized. fcMRI is particularly useful for characterizing large-scale systems that span distributed areas (e.g., polysynaptic cortical pathways, cerebro-cerebellar circuits, cortical-thalamic circuits) and has complementary strengths when contrasted with the other major tool available for human connectomics—high angular resolution diffusion imaging (HARDI). We review what is known about fcMRI and then explore fcMRI data reliability, effects of pre... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161546 Tue, 12 Jan 2010 00:12:42 +0100 3161546 http://www.medworm.com/index.php?rid=3161545&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F290%3Frss%3D1 The septohippocampal system has been implicated in the cognitive deficits associated with ethanol consumption, but the cellular basis of ethanol action awaits full elucidation. In the medial septum/diagonal band of Broca (MS/DB), a muscarinic tone, reflective of firing activity of resident cholinergic neurons, regulates that of their noncholinergic, putatively GABAergic, counterparts. Here we tested the hypothesis that ethanol alters this muscarinic tone. The spontaneous firing activity of cholinergic and noncholinergic MS/DB neurons were monitored in acute MS/DB slices from C57Bl/6 mice. Exposing the entire slice to ethanol increased firing in both cholinergic and noncholinergic neurons. However, applying ethanol focally to individual MS/DB neurons increased firing only in cholinergic neu... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161545 Tue, 12 Jan 2010 00:12:42 +0100 3161545 http://www.medworm.com/index.php?rid=3161544&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F278%3Frss%3D1 In humans, hand performance has evolved from a crude multidigit grasp to skilled individuated finger movements. However, control of the fingers is not completely independent. Although musculotendinous factors can limit independent movements, constraints in supraspinal control are more important. Most previous studies examined either flexion or extension of the digits. We studied differences in voluntary force production by the five digits, in both flexion and extension tasks. Eleven healthy subjects were instructed either to maximally flex or extend their digits, in all single- and multidigit combinations. They received visual feedback of total force produced by "instructed" digits and had to ignore "noninstructed" digits. Despite attempts to maximally flex or extend instructed digits, sub... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161544 Tue, 12 Jan 2010 00:12:42 +0100 3161544 http://www.medworm.com/index.php?rid=3161543&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F262%3Frss%3D1 We examined this possibility by recording neuronal activity and injecting muscimol into the caudal PMd (PMdc) of monkeys while they were performing a reaching task toward visuospatial targets with either the right or left arm, as instructed by low-frequency or high-frequency tone signals. Following the injection of a small amount of muscimol (1 µL; 5 µg/µL) into the unilateral PMdc, monkeys exhibited two major deficits in behavioral performance: 1) erroneous selection of the arm not indicated by the instruction (selection errors) and 2) no movement initiation in response to a visuospatial target cue serving as a trigger signal for reaching within the reaction time limit (movement initiation errors). Errors were observed following unilateral muscimol injection into both ri... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161543 Tue, 12 Jan 2010 00:12:42 +0100 3161543 http://www.medworm.com/index.php?rid=3161542&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F250%3Frss%3D1 The granular layer of cerebellum has been long hypothesized to perform combinatorial operations on incoming signals. Although this assumption is at the basis of main computational theories of cerebellum, it has never been assessed experimentally. Here, by applying high-resolution voltage-sensitive dye imaging techniques, we show that simultaneous activation of two partially overlapping mossy fiber bundles (either with single pulses or high-frequency bursts) can cause combined excitation and combined inhibition, which are compatible with the concepts of coincidence detection and spatial pattern separation predicted by theory. Combined excitation appeared as an area in which the combination of two inputs is greater than the arithmetic sum of the individual inputs and was enhanced by -aminobu... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161542 Tue, 12 Jan 2010 00:12:42 +0100 3161542 http://www.medworm.com/index.php?rid=3161541&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F244%3Frss%3D1 The capability of involuntarily tracking certain sound signals during the simultaneous presence of noise is essential in human daily life. Previous studies have demonstrated that top-down auditory focused attention can enhance excitatory and inhibitory neural activity, resulting in sharpening of frequency tuning of auditory neurons. In the present study, we investigated bottom-up driven involuntary neural processing of sound signals in noisy environments by means of magnetoencephalography. We contrasted two sound signal sequencing conditions: "constant sequencing" versus "random sequencing." Based on a pool of 16 different frequencies, either identical (constant sequencing) or pseudorandomly chosen (random sequencing) test frequencies were presented blockwise together with band-eliminated ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161541 Tue, 12 Jan 2010 00:12:42 +0100 3161541 http://www.medworm.com/index.php?rid=3161540&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F230%3Frss%3D1 Visual motion signals, which are initially extracted in parallel at multiple spatial frequencies, are subsequently integrated into a unified motion percept. Cross-frequency integration plays a crucial role when directional information conflicts across frequencies due to such factors as occlusion. We investigated the human observers' open-loop oculomotor tracking responses (ocular following responses, or OFRs) and the perceived motion direction in an idealized situation of occlusion—multiple-slits viewing (MSV)—in which a moving pattern is visible only through an array of slits. We also tested a more challenging viewing condition, contrast-alternating MSV (CA-MSV), in which the contrast polarity of the moving pattern alternates when it passes the slits. We found that changes in ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161540 Tue, 12 Jan 2010 00:12:42 +0100 3161540 http://www.medworm.com/index.php?rid=3161539&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F218%3Frss%3D1 We examined the development of phase-locking of oscillatory responses to music sounds and to pure tones matched to the fundamental frequency of the music sounds. Phase-locking for theta (4–8 Hz), alpha (8–14 Hz), lower-to-mid beta (14–25 Hz), and upper-beta and gamma (25–70 Hz) bands strengthened with age. Phase-locking in the upper-beta and gamma range matured later than in lower frequencies and was stronger for music sounds than for pure tones, likely reflecting the maturation of neural networks that code spectral complexity. Phase-locking for theta, alpha, and lower-to-mid beta was sensitive to temporal onset (rise time) sound characteristics. The data were also consistent with phase-locked oscillatory effects of acoustic (spectrotemporal) complexity and timbre f... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161539 Tue, 12 Jan 2010 00:12:42 +0100 3161539 http://www.medworm.com/index.php?rid=3161538&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F206%3Frss%3D1 When both visual and proprioceptive information are available about the position of a part of the body, the brain weights and combines these sources to form a single estimate, often modeled by minimum variance integration. These weights are known to vary with different circumstances, but the type of information causing the brain to change weights (reweight) is unknown. Here we studied reweighting in the context of estimating the position of a hand for the purpose of reaching it with the other hand. Subjects reached to visual (V), proprioceptive (P), or combined (VP) targets in a virtual reality setup. We calculated weights for vision and proprioception by comparing endpoints on VP reaches with endpoints on P and V reaches. Endpoint visual feedback was manipulated to control completely for ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161538 Tue, 12 Jan 2010 00:12:42 +0100 3161538 http://www.medworm.com/index.php?rid=3161537&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F192%3Frss%3D1 For primary auditory cortex (AI) laminae, there is little evidence of functional specificity despite clearly expressed cellular and connectional differences. Natural sounds are dominated by dynamic temporal and spectral modulations and we used these properties to evaluate local functional differences or constancies across laminae. To examine the layer-specific processing of acoustic modulation information, we simultaneously recorded from multiple AI laminae in the anesthetized cat. Neurons were challenged with dynamic moving ripple stimuli and we subsequently computed spectrotemporal receptive fields (STRFs). From the STRFs, temporal and spectral modulation transfer functions (tMTFs, sMTFs) were calculated and compared across layers. Temporal and spectral modulation properties often differ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161537 Tue, 12 Jan 2010 00:12:42 +0100 3161537 http://www.medworm.com/index.php?rid=3161536&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F183%3Frss%3D1 New walking patterns can be learned over short time scales (i.e., adapted in minutes) using a split-belt treadmill that controls the speed of each leg independently. This leads to storage of a modified motor pattern that is expressed as an aftereffect in regular walking conditions and must be de-adapted to return to normal. Here we asked whether the nervous system adapts a general walking pattern that is used across many speeds or a specific pattern affecting only the two speeds experienced during split-belt training. In experiment 1, we tested three groups of healthy adult subjects walking at different split-belt speed combinations and then assessed aftereffects at a range of speeds. We found that aftereffects were largest at the slower speed that was used in split-belt training in all th... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161536 Tue, 12 Jan 2010 00:12:42 +0100 3161536 http://www.medworm.com/index.php?rid=3161535&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F172%3Frss%3D1 The sphenopalatine ganglion (SPG) neurons represent the parasympathetic branch of the autonomic nervous system involved in controlling cerebral blood flow. In the present study, we examined the coupling mechanism between mu (µ) opioid receptors (MOR) and muscarinic acetylcholine receptors (mAChR) with Ca2+ channels in acutely dissociated adult rat SPG neurons. Successful MOR activation was recorded in ~40–45% of SPG neurons employing the whole cell variant of the patch-clamp technique. In addition, immunofluorescence assays indicated that MOR are not expressed in all SPG neurons while M2 mAChR staining was evident in all neurons. The concentration-response relationships generated with morphine and [d-Ala2-N-Me-Phe4-Glycol5]-enkephalin (DAMGO) showed IC50 values of 15.2 and 56.1... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161535 Tue, 12 Jan 2010 00:12:42 +0100 3161535 http://www.medworm.com/index.php?rid=3161534&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F164%3Frss%3D1 The sense of limb position is crucial for movement control and environmental interactions. Our understanding of this fundamental proprioceptive process, however, is limited. For example, little is known about the accuracy of arm proprioception: Does it vary with changes in arm configuration, since some peripheral receptors are engaged only when joints move toward extreme angles? Are these variations consistent across different tasks? Does proprioceptive ability change depending on what we try to localize (e.g., fingertip position vs. elbow angle)? We used a robot exoskeleton to study proprioception in 14 arm configurations across three tasks, asking healthy subjects to 1) match a pointer to elbow angles after passive movements, 2) match a pointer to fingertip positions after passive moveme... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161534 Tue, 12 Jan 2010 00:12:42 +0100 3161534 http://www.medworm.com/index.php?rid=3161533&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F155%3Frss%3D1 In this study, we examined the expression of PAR4 in joints and dorsal root ganglion (DRG) neurons and whether activation of PAR4 has an effect on nociception in normal rat knee joints. Electrophysiological recordings were made from joint primary afferents in male Wistar rats during both nonnoxious and noxious rotations of the knee. Afferent firing rate was recorded for 15 min post close intra-arterial injection of 10–9–10–5 mol of the PAR4 activating peptide, AYPGKF-NH2, or the inactive peptide, YAPGKF-NH2 (100 µl bolus). Rats were either naive or pretreated with the selective PAR4 antagonist, pepducin P4pal-10, the transient receptor potential vanilloid-1 (TRPV1) antagonist, SB366791, or the bradykinin B2 receptor antagonist, HOE140. Immunofluorescence experiments... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161533 Tue, 12 Jan 2010 00:12:42 +0100 3161533 http://www.medworm.com/index.php?rid=3161532&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F140%3Frss%3D1 Perceptual learning involves long-lasting improvements in the ability to perceive simple sensory stimuli. Some forms of perceptual learning are thought to involve an increasingly selective readout of sensory neurons that are most sensitive to the trained stimulus. Here we report novel changes in the relationship between the threshold and slope of the psychometric function during learning that are consistent with such changes in readout and can provide insights into the underlying neural mechanisms. In monkeys trained on a direction-discrimination task, perceptual improvements corresponded to lower psychometric thresholds and slightly shallower slopes. However, this relationship between threshold and slope was much weaker in comparable, ideal-observer "neurometric" functions of neurons in t... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161532 Tue, 12 Jan 2010 00:12:42 +0100 3161532 http://www.medworm.com/index.php?rid=3161531&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F117%3Frss%3D1 Remapping of gaze-centered target-position signals across saccades has been observed in the superior colliculus and several cortical areas. It is generally assumed that this remapping is driven by saccade-related signals. What is not known is how the different potential forms of this signal (i.e., visual, visuomotor, or motor) might influence this remapping. We trained a three-layer recurrent neural network to update target position (represented as a "hill" of activity in a gaze-centered topographic map) across saccades, using discrete time steps and backpropagation-through-time algorithm. Updating was driven by an efference copy of one of three saccade-related signals: a transient visual response to the saccade-target in two-dimensional (2-D) topographic coordinates (Vtop), a temporally e... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161531 Tue, 12 Jan 2010 00:12:42 +0100 3161531 http://www.medworm.com/index.php?rid=3161530&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F108%3Frss%3D1 Moving our fingertips toward objects to produce well-directed forces immediately upon contact is fundamental to dexterous manipulation. This apparently simple motion-to-force transition in fact involves a time-critical, predictive switch in control strategy. Given that dexterous manipulation must accommodate multiple mechanical conditions, we investigated whether and how this transition adapts to task difficulty. Eight adults (19–39 yr) produced ramps of isometric vertical fingertip force against a rigid surface immediately following a tapping motion. By changing target surface friction and size, we defined an easier (sandpaper, 11 mm diam) versus a more difficult (polished steel, 5 mm diam) task. As in prior work, we assembled fine-wire electromyograms from all seven muscles of the ... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161530 Tue, 12 Jan 2010 00:12:42 +0100 3161530 http://www.medworm.com/index.php?rid=3161529&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F97%3Frss%3D1 Recent studies have reported the presence of single neurons with strong responses to visual inputs in the human medial temporal lobe. Here we show how repeated stimulus presentation—photos of celebrities and familiar individuals, landmark buildings, animals, and objects—modulates the firing rate of these cells: a consistent decrease in the neural activity was registered as images were repeatedly shown during experimental sessions. The effect of repeated stimulus presentation was not the same for all medial temporal lobe areas. These findings are consistent with the view that medial temporal lobe neurons link visual percepts to declarative memory. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161529 Tue, 12 Jan 2010 00:12:42 +0100 3161529 http://www.medworm.com/index.php?rid=3161528&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F83%3Frss%3D1 The neurogenic heart of decapod crustaceans is a very simple, self-contained, model central pattern generator (CPG)-effector system. The CPG, the nine-neuron cardiac ganglion (CG), is embedded in the myocardium itself; it generates bursts of spikes that are transmitted by the CG's five motor neurons to the periphery of the system, the myocardium, to produce its contractions. Considerable evidence suggests that a CPG-peripheral loop is completed by a return feedback pathway through which the contractions modify, in turn, the CG motor pattern. One likely pathway is provided by dendrites, presumably mechanosensitive, that the CG neurons project into the adjacent myocardial muscle. Here we have tested the role of this pathway in the heart of the blue crab, Callinectes sapidus. We performed "de... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161528 Tue, 12 Jan 2010 00:12:42 +0100 3161528 http://www.medworm.com/index.php?rid=3161527&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F74%3Frss%3D1 The question of whether skin receptors might help in the perception of muscle contraction and body movement has not been settled. The present study gives direct evidence of skin receptor firing in close coincidence with the contraction of the vaginal and anal sphincters. The distal stump of the sectioned motor pudendal nerve was stimulated. Single shocks induced a wavelike increase in the lumen pressure of the distal vagina and the anal canal, as well as constriction of the vaginal introitus and the anus. The constriction pulls on and moves the surrounding skin, which was initially detected visually. In the present experiments, a thin strain gauge that pressed on the skin surface detected its displacement. Single shocks to the motor nerve induced a wave of skin movement with maximal amplit... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161527 Tue, 12 Jan 2010 00:12:41 +0100 3161527 http://www.medworm.com/index.php?rid=3161526&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F65%3Frss%3D1 Deafferentation such as the amputation of a body part causes cortical reorganization in the primary motor cortex (M1). We investigated whether this reorganization is reversible after reconstruction of the lost body part. We tested two patients who had long-standing thumb amputations followed by thumb reconstruction with toe-to-thumb transfer 9 to 10 mo later and one patient who underwent thumb replantation immediately following traumatic amputation. Using transcranial magnetic stimulation, we measured the motor evoked potential (MEP) threshold, latency, short-interval intracortical inhibition (SICI), and intracortical facilitation (ICF) at different time points in the course of recovery in abductor pollicis brevis muscle. For the two patients who underwent late toe-to-thumb transfer, the r... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161526 Tue, 12 Jan 2010 00:12:41 +0100 3161526 http://www.medworm.com/index.php?rid=3161525&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F55%3Frss%3D1 Real lines and illusory contours (ICs) have been reported to either interfere with or facilitate the perception of the other, depending on real line orientation and contrast. Here we investigate contextual effects of real lines on illusory contour perception. Curvature discrimination thresholds of Kanizsa-contours were measured for superimposed real lines of different sub- and suprathreshold contrasts. We find that parallel lines interfere with curvature discrimination at suprathreshold, whereas orthogonal lines interfere at subthreshold contrasts. We did not find stable facilitating effects of lines in any orientation or contrast. These results are discussed in relation to existing physiological and imaging data. (Source: Journal of Neurophysiology) Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161525 Tue, 12 Jan 2010 00:12:41 +0100 3161525 http://www.medworm.com/index.php?rid=3161524&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F47%3Frss%3D1 The cellular mechanisms that mediate spike timing–dependent plasticity (STDP) are largely unknown. We studied in vitro in CA1 pyramidal neurons the contribution of AMPA and N-methyl-d-aspartate (NMDA) components of Schaffer collateral (SC) excitatory postsynaptic potentials (EPSPs; EPSPAMPA and EPSPNMDA) and of the back-propagating action potential (BAP) to the long-term potentiation (LTP) induced by a STDP protocol that consisted in pairing an EPSP and a BAP. Transient blockade of EPSPAMPA with 7-nitro-2,3-dioxo-1,4-dihydroquinoxaline-6-carbonitrile (CNQX) during the STDP protocol prevented LTP. Contrastingly LTP was induced under transient inhibition of EPSPAMPA by combining SC stimulation, an imposed EPSPAMPA-like depolarization, and BAP or by coupling the EPSPNMDA evoked under su... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161524 Tue, 12 Jan 2010 00:12:41 +0100 3161524 http://www.medworm.com/index.php?rid=3161523&cid=s_33709_25_f&fid=33709&url=http%3A%2F%2Fjn.physiology.org%2Fcgi%2Fcontent%2Fabstract%2F103%2F1%2F38%3Frss%3D1 Sensory systems use a variety of strategies to increase the signal-to-noise ratio in their inputs at the receptor level. However, important cues for sound localization are not present at the individual ears but are computed after inputs from the two ears converge within the brain, and we hypothesized that additional strategies to enhance the representation of these cues might be employed in the initial stages after binaural convergence. Specifically, we investigated the transformation that takes place between the first two stages of the gerbil auditory pathway that are sensitive to differences in the arrival time of a sound at the two ears (interaural time differences; ITDs): the medial superior olive (MSO), where ITD tuning originates, and the dorsal nucleus of the lateral lemniscus (DNLL... Journal of Neurophysiology journals http://www.medworm.com/rss/comments.php?id=3161523 Tue, 12 Jan 2010 00:12:41 +0100 3161523