bluuebunny/crossref_metadata_2025 huggingface dataset:
Initiation of Spontaneous Epileptiform Activity in the Neocortical Slice
Authors: Tsau Yang , Guan Li , Wu Jian-Young
Published: December 2017

Tsau, Yang, Li Guan, and Jian-Young Wu. Initiation of spontaneous epileptiform activity in the neocortical slice. J. Neurophysiol. 80: 978–982, 1998. Cortical local circuitry is important in epileptogenesis. Voltage-sensitive dyes and fast imaging were used to visualize the initiation of spontaneous paroxysmal events in adult rat neocortical slices. Although spontaneous paroxysmal events could start from anywhere in the preparation, optical imaging revealed that all spontaneous events started at a few confined initiation foci and propagated to the whole preparation. Multielectrode recording over hundreds of spontaneous events revealed that often two or three initiation foci coexisted in each preparation ( n = 10). These foci took turns being dominant; the dominant focus initiated the majority of the spontaneous paroxysmal events during that period. The dominant focus and dynamic rearrangement of foci suggest that the initiation of spontaneous epileptiform events involves a local multineuronal process, perhaps with potentiated synapses.
Suppression of NMDA Receptor Function Using Antisense DNA Blocks Ocular Dominance Plasticity While Preserving Visual Responses
Authors: Roberts Elizabeth B. , Meredith M. Alex , Ramoa Ary S.
Published: December 2017

Roberts, Elizabeth B., M. Alex Meredith, and Ary S. Ramoa. Suppression of NMDA receptor function using antisense DNA blocks ocular dominance plasticity while preserving visual responses. J. Neurophysiol. 80: 1021–1032, 1998. Pioneering work has shown that pharmacological blockade of the N-methyl-d-aspartate (NMDA) receptor channel reduces ocular dominance plasticity. However, the results also show that doses of NMDA receptor antagonists that have an effect on ocular dominance plasticity profoundly reduce sensory responses and disrupt stimulus selectivity of cortical cells. It is, therefore, not possible to determine whether effects of NMDA receptor blockade on visual plasticity result from a specific role of NMDA receptors or from the reduction in sensory response. We have used an alternate approach to examine this question. We performed knockdown experiments using antisense oligodeoxynucleotides (ODNs) complementary to mRNA coding the NR1 subunit of the NMDA receptor. After 5 days of antisense, but not sense, ODN treatment NMDA receptor–mediated synaptic transmission was reduced markedly relative to the α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor response, as indicated by whole cell patch-clamp recordings in the cortical slice preparation. This suppression of NMDA receptor–mediated currents was due to a selective reduction in the NR1 protein near the injection site relative to the untreated hemisphere in the same animal, as indicated by immunocytochemistry and Western blotting. In contrast, AMPA receptors were not affected by the antisense ODN treatment indicating specificity of effects. Another major effect of this treatment was to decrease ocular dominance plasticity. Ferrets that were monocularly deprived 1 wk during the antisense ODN treatment had ocular dominance histograms similar to those found in untreated, nondeprived animals. In contrast, ferrets treated with sense ODN and monocularly deprived had ocular dominance histograms resembling those of untreated, monocularly deprived animals. The effects on ocular dominance plasticity did not result from a disruption of sensory responses because maximum responses as well as orientation and direction selectivity of cortical cells were not affected by the treatment. In conclusion, the present results show that antisense techniques can accomplish more selective manipulations of cortical function than is possible with traditional pharmacological agents. Use of this approach also provides unambiguous evidence for a specific role of NMDA receptors in visual plasticity.
Kinetic and Stochastic Properties of a Persistent Sodium Current in Mature Guinea Pig Cerebellar Purkinje Cells
Authors: Kay Alan R. , Sugimori Mutsuyuki , Llinás Rodolfo
Published: December 2017

Kay, Alan R., Mutsuyuki Sugimori, and Rodolfo Llinás. Kinetic and stochastic properties of a persistent sodium current in mature guinea pig cerebellar Purkinje cells. J. Neurophysiol. 80: 1167–1179, 1998. Whole cell voltage-clamp techniques were employed to characterize the sodium (Na) conductances in acutely dissociated, mature guinea-pig cerebellar Purkinje cells. Three phenomenological components were noted: two inactivating and a persistent component ( I P Na). All exhibited similar sensitivities to tetrodotoxin (TTX; IC50 ∼3 nM). The inactivating Na current demonstrates two components with different rates of inactivation. The persistent component activates at a more negative membrane potential than the inactivating components and shows little inactivation during a 5-s pulse. The amplitude of the persistent Na conductance had a higher Q 10 than the inactivating Na conductance (2.7 vs. 1.3). I P Na rapidly activates (∼1 ms) and deactivates (<0.2 ms) and like the fast component appears to be exclusively Na permeable. I P Na is not a “window” current because its range of activation exceeds the small overlap between the steady-state activation and inactivation characteristics of the inactivating current. Anomalous tail currents were observed during voltage pulses above –40 mV after a prepulse above –30 mV. The tails rose to a maximum inward current with a time constant of 1.5 ms and decayed to a persistent inward current with a time constant of 20 ms. The tails probably arose as a result of recovery from inactivation through the open state. The noise characteristics of I P Na were anomalous in that the measured variance was lower at threshold voltages than would be predicted by a binomial model. The form of the variance could be partially accounted for by postulating that the maximum probability of activation of the persistent current was less than unity. The noise characteristics of I P Na are such as to minimize noise near spike activation threshold and sharpen the threshold.
Recovery of Locomotion After Ventral and Ventrolateral Spinal Lesions in the Cat. I. Deficits and Adaptive Mechanisms
Authors: Brustein Edna , Rossignol Serge
Published: December 2017

Brustein, Edna and Serge Rossignol. Recovery of locomotion after ventral and ventrolateral spinal lesions in the cat. I. Deficits and adaptive mechanisms. J. Neurophysiol. 80: 1245–1267, 1998. The recovery of treadmill locomotion of eight adult cats, subjected to chronic ventral and ventrolateral spinal lesions at low thoracic levels (T11or T13), preserving at least one dorsolateral funiculus and the dorsal columns, was documented daily using electromyographic (EMG) and kinematic methods. The data show that all cats eventually recovered quadrupedal voluntary locomotion despite extensive damage to important pathways (such as the reticulospinal and the vestibulospinal) as verified by injection of wheat germ agglutinin–horseradish peroxidase (WGA-HRP) caudal to the site of lesion. Initially (in the early period after the spinal lesion), all the cats suffered from pronounced locomotor and postural deficits, and they could not support their hindquarters or walk with their hindlimbs. Gradually, during the recovery period, they regained quadrupedal walking, although their locomotion was wobbly and inconsistent, and they suffered from poor lateral stability. EMG and kinematic data analyses showed a tendency for an increase in the variability of the step cycle duration but no major changes in the step cycle structure or in the intralimb coupling of the joints. However, the homolateral fore- and hindlimb coupling was highly perturbed in cats with the largest lesions. Although the general alternating pattern of extensor and flexors was maintained, there were various changes in the duration and amplitude of the EMG bursts as well as a lack of amplitude modulation during walking uphill or downhill on the treadmill. In cats with larger lesions, the forelimbs also seem to take a greater propulsive role than usual as revealed by a consistent increase of the activity of the triceps. In cats with smaller lesions, these deficits were transient, but, for the most extensively lesioned cats, they were pronounced and lasted long term postlesion even after reaching a more or less stable locomotor behavior (plateau period). It is concluded that recovery of quadrupedal locomotion is possible even after a massive lesion to ventral and ventrolateral quadrants, severing the vestibulospinal pathway and causing severe, although incomplete, damage to the reticulospinal tract. The quick recovery in the less lesioned cats can be attributed to remaining pathways normally implicated in locomotor function. However, in the most extensively lesioned cats, the long period of recovery and the pronounced deficits during the plateau period may indicate that the compensation, attributed to remaining reticulospinal pathways, is not sufficient and that other pathways in the dorsolateral funiculi, such as the corticospinal, can sustain and adapt, up to a certain extent, the voluntary quadrupedal walking.
Mechanisms of Afterhyperpolarization in Lobster Olfactory Receptor Neurons
Authors: Corotto Frank S. , Michel William C.
Published: December 2017

Corotto, Frank S. and William C. Michel. Mechanisms of afterhyperpolarization in lobster olfactory receptor neurons. J. Neurophysiol. 80: 1268–1276, 1998. In lobster olfactory receptor neurons (ORNs), depolarizing responses to odorants and current injection are accompanied by the development of an afterhyperpolarization (AHP) that likely contributes to spike-frequency adaptation and that persists for several seconds after termination of the response. A portion of the AHP can be blocked by extracellular application of 5 mM CsCl. At this concentration, CsCl specifically blocks the hyperpolarization-activated cation current ( Ih) in lobster ORNs. This current is likely to be active at rest, where it provides a constant, depolarizing influence. Further depolarization deactivates Ih, thus allowing the cell to be briefly hyperpolarized when that depolarizing influence is removed, thus generating an AHP. Reactivation of Ihwould terminate the AHP. The component of the AHP that could not be blocked by Cs+(the Cs+-insensitive AHP) was accompanied by decreased input resistance, suggesting that this component is generated by increased conductance to an ion with an equilibrium potential more negative than the resting potential. The Cs+-insensitive AHP in current clamp and the underlying current in voltage clamp displayed a reversal potential of approximately –75 mV. Both EKand EClare predicted to be in this range. Similar results were obtained with the use of a high Cl–pipette solution, although that shifted EClfrom –72 mV to –13 mV. However, when EKwas shifted to more positive or negative values, the reversal potential also shifted accordingly. A role for the Ca2+-mediated K+current in generating the Cs+-independent AHP was explored by testing cells in current and voltage clamp while blocking IK(Ca)with Cs+/Co2+-saline. In some cells, the Cs+-independent AHP and its underlying current could be completely and reversibly blocked by Cs+/Co2+saline, whereas in other cells some fraction of it remained. This indicates that the Cs+-independent AHP results from two K+currents, one that requires an influx of extracellular Ca2+and one that does not. Collectively, these findings indicate that AHPs result from three phenomena that occur when lobster ORNs are depolarized: 1) inactivation of the hyperpolarization-activated cation current, 2) activation of a Ca2+-mediated K+current, and 3) activation of a K+current that does not require influx of extracellular Ca2+. Roles of these processes in modulating the output of lobster ORNs are discussed.
Analysis of Excitatory and Inhibitory Spontaneous Synaptic Activity in Mouse Retinal Ganglion Cells
Authors: Tian Ning , Hwang Thomas N. , Copenhagen David R.
Published: December 2017

Tian, Ning, Thomas N. Hwang, and David R. Copenhagen. Analysis of excitatory and inhibitory spontaneous synaptic activity in mouse retinal ganglion cells. J. Neurophysiol. 80: 1327–1340, 1998. Spontaneous inhibitory and excitatory postsynaptic currents (sIPSCs and sEPSCs) were identified and characterized with whole cell and perforated patch voltage-clamp recordings in adult mouse retinal ganglion cells. Pharmacological dissection revealed that all cells were driven by spontaneous synaptic inputs mediated by glutamate and γ-aminobutyric acid-A (GABAA) receptors. One-half (7/14) of the cells also received glycinergic spontaneous synaptic inputs. Both GABAA and glycine receptor–mediated sIPSCs had rise times (10–90%) of <1 ms. The decay times of the GABAA receptor–mediated sIPSCs were comparable with those of the glycine receptor–mediated sIPSCs. The average decay time constant for monoexponentially fitted sIPSCs was 63.2 ± 74.1 ms (mean ± SD, n = 3278). Glutamate receptor–mediated sEPSCs had an average rise time of 0.50 ± 0.20 ms ( n = 109) and an average monoexponential decay time constant of 5.9 ± 8.6 ms ( n = 2705). Slightly more than two-thirds of the spontaneous synaptic events were monoexponential (68% for sIPSCs and 76% for sEPSCs). The remainder of the events was biexponential. The amplitudes of the spontaneous synaptic events were not correlated with rise times, suggesting that the electrotonic filtering properties of the neurons and/or differences in the spatial location of synaptic inputs could not account for the difference between the decay time constants of the glutamate and GABAA/glycine receptor–mediated spontaneous synaptic events. The amplitudes of sEPSCs were similar to those recorded in tetrodotoxin (TTX), consistent with the events measured in control saline being the response to the release of a single quantum of transmitter. The range of the sIPSC amplitudes in control saline was wider than that recorded in TTX, consistent with some sIPSCs being evoked by presynaptic spikes having an average quantal size greater than one. The rates of sIPSCs and sEPSCs were determined under equivalent conditions by recording with perforated patch electrodes at potentials at which both types of event could be identified. Two groups of ganglion cell were observed; one group had an average sEPSCs/sIPSCs frequency ratio of 0.96 ± 0.77 ( n = 28) and another group had an average ratio of 6.63 ± 0.82 ( n = 7). These findings suggest that a subset of cells is driven much more strongly by excitatory synaptic inputs. We propose that this subset of cells could be off ganglion cells, consistent with the higher frequency of spontaneous action potentials found in off ganglion cells in other studies.
Amiloride Blocks Acid Responses in NaCl-Best Gustatory Neurons of the Hamster Solitary Nucleus
Authors: Boughter John D. , Smith David V.
Published: December 2017

Boughter, John D., Jr. and David V. Smith. Amiloride blocks acid responses in NaCl-best gustatory neurons of the hamster solitary nucleus. J. Neurophysiol. 80: 1362–1372, 1998. Biophysical studies of isolated taste receptor cells show that one mechanism of Na+ salt transduction involves the inward movement of Na+ through amiloride-blockable ion channels on the apical receptor cell membrane, which leads to a direct depolarization. Hamster taste receptor cells with amiloride-blockable Na+ responses also show an amiloride-sensitive H+ current. Thus one mechanism for the transduction of acid taste involves the amiloride-sensitive channel. We investigated the effects of amiloride on responses to acids in neurons of the nucleus of the solitary tract (NST) of the hamster. The responses of 47 NST neurons were recorded extracellularly while the anterior tongue was stimulated with solutions representing the four taste qualities (NaCl, sucrose, HCl, quinine), which were used to characterize each cell on the basis of its best stimulus. The effects of amiloride on responses to 10 mM HCl, 10 mM citric acid, 100 mM NaCl, and 100 mM sucrose were then investigated. Stimuli were presented alone for 30 s (control trials) and also presented for 10 s, followed by a mixture of the stimulus with 10 μM amiloride for 10 s, followed by the stimulus alone again for 10 s (amiloride trials). The effects of amiloride were assessed by comparing the responses of cells with the stimulus + amiloride with that of the stimulus alone. In neurons classified as NaCl-best, amiloride reversibly blocked responses to NaCl, HCl, and citric acid. In HCl-best neurons, amiloride had no effect on responses to any of these stimuli. In sucrose-best neurons, amiloride blocked the response to NaCl but not to sucrose or to either acid. These results support the hypothesis that acids are transduced by at least two different receptor mechanisms in the hamster, amiloride sensitive and amiloride insensitive. At the NST, these inputs are tightly maintained in two separate populations of neurons. Sucrose-best neurons, which show amiloride effects on NaCl but not acids, appear to receive converging inputs from both amiloride-sensitive (N-best) and amiloride-insensitive (H-best) chorda tympani nerve fibers.
Dependence on Target Configuration of Express Saccade-Related Activity in the Primate Superior Colliculus
Authors: Edelman Jay A. , Keller Edward L.
Published: December 2017

Edelman, Jay A. and Edward L. Keller. Dependence on target configuration of express saccade-related activity in the primate superior colliculus. J. Neurophysiol. 80: 1407–1426, 1998. To help understand how complex visual stimuli are processed into short-latency saccade motor programs, the activity of visuomotor neurons in the deeper layers of the superior colliculus was recorded while two monkeys made express saccades to one target and to two targets. It has been shown previously that the visual response and perimotor discharge characteristic of visuomotor neurons temporally coalesce into a single burst of discharge for express saccades. Here we seek to determine whether the distributed visual response to two targets spatially coalesces into a command appropriate for the resulting saccade. Two targets were presented at identical radial eccentricities separated in direction by 45°. A gap paradigm was used to elicit express saccades. Express saccades were more likely to land in between the two targets than were saccades of longer latency. The speeds of express saccades to two targets were similar to those of one target of similar vector, as were the trajectories of saccades to one and two targets. The movement fields for express saccades to two targets were more broad than those for saccades to one target for all neurons studied. For most neurons, the spatial pattern of discharge for saccades to two targets was better explained as a scaled version of the visual response to two spatially separate targets than as a scaled version of the perimotor response accompanying a saccade to a single target. Only the discharge of neurons with large movement fields could be equally well explained as a visual response to two targets or as a perimotor response for a one-target saccade. For most neurons, the spatial properties of discharge depended on the number of targets throughout the entire saccade-related burst. These results suggest that for express saccades to two targets the computation of saccade vector is not complete at the level of the superior colliculus for most neurons and an explicit process of target selection is not necessary at this level for the programming of an express saccade.
Resonance Effect for Neural Spike Time Reliability
Authors: Hunter John D. , Milton John G. , Thomas Peter J. , Cowan Jack D.
Published: December 2017

Hunter, John D., John G. Milton, Peter J. Thomas, and Jack D. Cowan. Resonance effect for neural spike time reliability. J. Neurophysiol. 80: 1427–1438, 1998. The spike timing reliability of Aplysia motoneurons stimulated by repeated presentation of periodic or aperiodic input currents is investigated. Two properties of the input are varied, the frequency content and the relative amplitude of the fluctuations to the mean (expressed as the coefficient of variation; CV). It is shown that, for small relative amplitude fluctuations (CV ≈ 0.05–0.15), the reliability of spike timing is enhanced if the input contains a resonant frequency equal to the firing rate of the neuron in response to the DC component of the input. This resonance-related enhancement in reliability decreases as the relative amplitude of the fluctuations increases (CV → 1). Similar results were obtained for a leaky integrate-and-fire neuronal model, suggesting that these effects are a general property of encoders that combine a threshold with a leaky integrator. These observations suggest that, when the magnitude of input fluctuations is small, changes in the power spectrum of the current fluctuations or in the spike discharge rate can have a pronounced effect on the ability of the neuron to encode a time-varying input with reliably timed spikes.
Spike-Wave Complexes and Fast Components of Cortically Generated Seizures. III. Synchronizing Mechanisms
Authors: Neckelmann Dag , Amzica Florin , Steriade Mircea
Published: December 2017

Neckelmann, Dag, Florin Amzica, and Mircea Steriade. Spike-wave complexes and fast components of cortically generated seizures. III. Synchronizing mechanisms. J. Neurophysiol. 80: 1480–1494, 1998. The intracortical and thalamocortical synchronization of spontaneously occurring or bicuculline-induced seizures, consisting of spike-wave (SW) or polyspike-wave (PSW) complexes at 2–3 Hz and fast runs at 10–15 Hz, was investigated in cats under ketamine-xylazine anesthesia. We used single and dual simultaneous intracellular recordings from cortical areas 5 and 7, and extracellular recordings of unit firing and field potentials from neocortical areas 5, 7, 17, 18, as well as related thalamic nuclei. The evolution of time delays between paroxysmal depolarizing events in single neurons or neuronal pools recorded from adjacent and distant sites was analyzed by using 1) sequential cross-correlations between field potentials, 2) averaged activities triggered by the spiky component of cortical SW/PSW complexes, and 3) time histograms between neuronal discharges. In all instances, the paroxysmal activities recorded from the dorsal thalamus lagged the onset of seizures in neocortex. The time lags between simultaneously impaled cortical neurons were significantly smaller during SW complexes than during the prior epochs of slow oscillation. During seizures, as during the slow oscillation, the intracortical synchrony was reduced with increased distance between different cortical sites. Dual intracellular recordings showed that, during the same seizure, time lags were not constant and, instead, reflected alternating precession of the recorded foci. After transection between areas 5 and 7, the intracortical synchrony was lost, but corticothalamocortical volleys could partially restore seizure synchrony. These data show that the neocortex leads the thalamus during SW/PSW seizures, that time lags between cortical foci are not static, and that thalamus may assist synchronization of SW/PSW seizures after disconnection of intracortical synaptic linkages.
Alterations in the Balance of Protein Kinase/Phosphatase Activities Parallel Reduced Synaptic Strength During Aging
Authors: Norris Christopher M. , Halpain Shelley , Foster Thomas C.
Published: December 2017

Norris, Christopher M., Shelley Halpain, and Thomas C. Foster. Alterations in the balance of protein kinase/phosphatase activities parallel reduced synaptic strength during aging. J. Neurophysiol. 80: 1567–1570, 1998. The current research examined the regulation of synaptic strength by protein phosphorylation during aging. Bath application of the protein phosphatase 1 and 2A (PP1 and PP2A) inhibitor calyculin A (1 μM) enhanced CA3–CA1 synaptic strength in hippocampal slices from aged male (20–24 mo) but not from young adult male (4–6 mo) Fischer 344 rats. Similarly, injection of the PP1 and PP2A inhibitor microcystin–L,R (5 μM) into CA1 cells caused an increase in the intracellular synaptic response only in slices from aged rats. In contrast, bath application of the serine/threonine kinase inhibitor H-7 (10 μM) induced a decrease in synaptic strength only in slices from the young adult group. These results demonstrate that phosphorylation-dependent regulation of intrinsic synaptic efficacy changes during aging.
GABABReceptor-Mediated Modulation of Presynaptic Currents and Excitatory Transmission at a Fast Central Synapse
Authors: Isaacson Jeffry S.
Published: December 2017

Isaacson, Jeffry S. GABABreceptor-mediated modulation of presynaptic currents and excitatory transmission at a fast central synapse. J. Neurophysiol. 80: 1571–1576, 1998. Large nerve terminals (calyces of Held) in the medial nucleus of the trapezoid body (MNTB) offer a unique opportunity to explore the modulation of presynaptic channels at a mammalian central synapse. In this study I examined γ-aminobutyric acid-B (GABAB)-mediated presynaptic inhibition at the calyx of Held in slices of the rat auditory brain stem. The selective GABABagonist baclofen caused a potent inhibition of synaptic transmission and presynaptic Ca2+current. The inhibition of presynaptic Ca2+channels was associated with a slowing of the activation kinetics of the underlying current, and the inhibition was relieved by strong depolarization. The inhibition of both synaptic transmission and presynaptic Ca2+current was abolished by N-ethylmaleimide, a sulfhydryl alkylating agent that uncouples the Go/Giclass of G proteins from receptors. Baclofen does not activate a potassium conductance in the presynaptic terminal. Taken together, these results suggest that GABABreceptors inhibit synaptic transmission via G protein-mediated modulation of presynaptic Ca2+channels at this large central synapse. Furthermore, these findings demonstrate that basic mechanisms of G protein-mediated inhibition of Ca2+channels, proposed from recordings of neuron cell bodies, are well conserved at nerve endings in the mammalian brain.
Efference Copy Provides the Eye Position Information Required for Visually Guided Reaching
Authors: Lewis Richard F. , Gaymard Bertrand M. , Tamargo Rafael J.
Published: December 2017

Lewis, Richard F., Bertrand M. Gaymard, and Rafael J. Tamargo. Efference copy provides the eye position information required for visually guided reaching. J. Neurophysiol. 80: 1605–1608, 1998. The contribution of extraocular muscle (EOM) proprioception to the eye position signal used to transform retinotopic visual information to a craniotopic reference frame remains uncertain. In this study we examined the effects of unilateral and bilateral proprioceptive deafferentation of the EOMs on the accuracy of reaching movements directed to visual targets. No significant changes occurred in the mean accuracy (constant error) or variance (variable error) of pointing after unilateral or bilateral deafferentation. We concluded that in normal animals efference copy provides sufficient information about orbital eye position to code space in craniotopic coordinates.
Analysis of the Role of Inhibition in Shaping Responses to Sinusoidally Amplitude-Modulated Signals in the Inferior Colliculus
Authors: Burger R. Michael , Pollak George D.
Published: December 2017

Burger, R. Michael and George D. Pollak. Analysis of the role of inhibition in shaping responses to sinusoidally amplitude-modulated signals in the inferior colliculus. J. Neurophysiol. 80: 1686–1701, 1998. Neurons in the central nucleus of the inferior colliculus (ICc) typically respond with phase-locked discharges to low rates of sinusoidal amplitude-modulated (SAM) signals and fail to phase-lock to higher SAM rates. Previous studies have shown that comparable phase-locking to SAM occurs in the dorsal nucleus of the lateral lemniscus (DNLL) and medial superior olive (MSO) of the mustache bat. The studies of MSO and DNLL also showed that the restricted phase-locking to low SAM rates is created by the coincidence of phase-locked excitatory and inhibitory inputs that have slightly different latencies. Here we tested the hypothesis that responses to SAM in the mustache bat IC are shaped by the same mechanism that shapes responses to SAM in the two lower nuclei. We recorded responses from ICc neurons evoked by SAM signals before and during the iontophoretic application of several pharmacological agents: bicuculline, a competitive antagonist for γ-aminobutyric acid-A (GABAA) receptors; strychnine, a competitive antagonist for glycine receptors; the GABAB receptor blocker, phaclofen, and the N-methyl-d-aspartate (NMDA) receptor blocker, (−)-2-amino-5-phosphonopentanoic acid (AP5). The hypothesis that inhibition shapes responses to SAM signals in the ICc was not confirmed. In >90% of the ICc neurons tested, the range of SAM rates to which they phase-locked was unchanged after blocking inhibition with bicuculline, strychnine or phaclofen, applied either individually or in combination. We also considered the possibility that faster α-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA) receptors follow high temporal rates of incoming excitation but that the slower NMDA receptors could follow only lower rates. Thus at higher SAM rates, NMDA receptors might generate a sustained excitation that “smears” the phase-locked excitation generated by the AMPA receptors. The NMDA hypothesis, like the inhibition hypothesis, was also not confirmed. In none of the cells that we tested did the application of AP5 by itself, or in combination with bicuculline, cause an increase in the range of SAM rates that evoked phase-locking. These results illustrate that the same response property, phase-locking restricted to low SAM rates, is formed in more than one way in the auditory brain stem. In the MSO and DNLL, the mechanism is coincidence of phase-locked excitation and inhibition, whereas in ICc the same response feature is formed by a different but unknown mechanism.
Intracellular pH Buffering Shapes Activity-Dependent Ca2+Dynamics in Dendrites of CA1 Interneurons
Authors: Tombaugh Geoffrey C.
Published: December 2017

Tombaugh, Geoffrey C. Intracellular pH buffering shapes activity-dependent Ca2+dynamics in dendrites of CA1 interneurons. J. Neurophysiol. 80: 1702–1712, 1998. Voltage-gated calcium (Ca) channels are highly sensitive to cytosolic H+, and Ca2+influx through these channels triggers an activity-dependent fall in intracellular pH (pHi). In principle, this acidosis could act as a negative feedback signal that restricts excessive Ca2+influx. To examine this possibility, whole cell current-clamp recordings were taken from rat hippocampal interneurons, and dendritic Ca2+transients were monitored fluorometrically during spike trains evoked by brief depolarizing pulses. In cells dialyzed with elevated internal pH buffering (high β), trains of >15 action potentials (Aps) provoked a significantly larger Ca2+transient. Voltage-clamp analysis of whole cell Ca currents revealed that differences in cytosolic pH buffering per se did not alter baseline Ca channel function, although deliberate internal acidification by 0.3 pH units blunted Ca currents by ∼20%. APs always broadened during a spike train, yet this broadening was significantly greater in high β cells during rapid but not slow firing rates. This effect of internal β on spike repolarization could be blocked by cadmium. High β also 1) enhanced the slow afterhyperpolarization (sAHP) seen after a spike train and 2) accelerated the decay of an early component of the sAHP that closely matched a sAHP conductance that could be blocked by apamin. Both of these effects on the sAHP could be detected at high but not low firing rates. These data suggest that activity-dependent pHishifts can blunt voltage-gated Ca2+influx and retard submembrane Ca2+clearance, suggesting a novel feedback mechanism by which Ca2+signals are shaped and coupled to the level of cell activity.
Electrical Microstimulation Distinguishes Distinct Saccade-Related Areas in the Posterior Parietal Cortex
Authors: Thier Peter , Andersen Richard A.
Published: December 2017

Thier, Peter and Richard A. Andersen. Electrical microstimulation distinguishes distinct saccade-related areas in the posterior parietal cortex. J. Neurophysiol. 80: 1713–1735, 1998. Electrical microstimulation (0.1-ms bipolar pulses at 500 Hz, current strength usually between 100 and 200 μA) was used to delineate saccade-related areas in the posterior parietal cortex of monkeys. Stimulation-induced saccades were found to be restricted to the lateral intraparietal area (area LIP) in the intraparietal sulcus (IPS) and a region on the medial aspect of the parietal lobe (area MP, medial parietal area), close to the caudal end of the cingulate sulcus, whereas stimulation of area 7a did not evoke eye movements. Two different types of evoked saccades were observed. Modified vector saccades, whose amplitude was modified by the position of the eyes at stimulation onset were the hallmark of sites in area LIP and area MP. The same sites were characterized by a propensity of single units active in the memory and presaccadic response segments of the memory saccade paradigm. Goal-directed saccades driving the eyes toward a circumscribed region relative to the head were largely restricted to a small strip of cortex on the lateral bank and the floor of the IPS (the intercalated zone), separating the representation of upward and downward directed saccades in LIP. Unlike stimulation in LIP or MP, stimulation in the intercalated zone gave rise to head, pinnae, facial, and shoulder movements accompanying the evoked saccades. We propose that the amplitude modification of vector saccades characterizing LIP and MP may reflect a spatially distributed head-centered coding scheme for saccades. On the other hand, the goal-directed saccades found in the intercalated zone could indicate the use of a spatially much more localized representation of desired location in head-centered space.
Net Interaction Between Different Forms of Short-Term Synaptic Plasticity and Slow-IPSPs in the Hippocampus and Auditory Cortex
Authors: Buonomano Dean V. , Merzenich Michael M.
Published: December 2017

Buonomano, Dean V. and Michael M. Merzenich. Net interaction between different forms of short-term synaptic plasticity and slow-IPSPs in the hippocampus and auditory cortex. J. Neurophysiol. 80: 1765–1774, 1998. Paired-pulse plasticity is typically used to study the mechanisms underlying synaptic transmission and modulation. An important question relates to whether, under physiological conditions in which various opposing synaptic properties are acting in parallel, the net effect is facilitatory or depressive, that is, whether cells further or closer to threshold. For example, does the net sum of paired-pulse facilitation (PPF) of excitatory postsynaptic potentials (EPSPs), paired-pulse depression (PPD) of inhibitory postsynaptic potentials (IPSPs), and the hyperpolarizing slow IPSP result in depression or facilitation? Here we examine how different time-dependent properties act in parallel and examine the contribution of γ-aminobutyric acid-B (GABAB) receptors that mediate two opposing processes, the slow IPSP and PPD of the fast IPSP. Using intracellular recordings from rat CA3 hippocampal neurons and L-II/III auditory cortex neurons, we examined the postsynaptic responses to paired-pulse stimulation (with intervals between 50 and 400 ms) of the Schaffer collaterals and white matter, respectively. Changes in the amplitude, time-to-peak (TTP), and slope of each EPSP were analyzed before and after application of the GABAB antagonist CGP-55845. In both CA3 and L-II/III neurons the peak amplitude of the second EPSP was generally depressed (further from threshold) compared with the first at the longer intervals; however, these EPSPs were generally broader and exhibited a longer TTP that could result in facilitation by enhancing temporal summation. At the short intervals CA3 neurons exhibited facilitation of the peak EPSP amplitude in the absence and presence of CGP-55845. In contrast, on average L-II/III cells did not exhibit facilitation at any interval, in the absence or presence of CGP-55845. CGP-55845 generally “erased” short-term plasticity, equalizing the peak amplitude and TTP of the first and second EPSPs at longer intervals in the hippocampus and auditory cortex. These results show that it is necessary to consider all time-dependent properties to determine whether facilitation or depression will dominate under intact pharmacological conditions. Furthermore our results suggest that GABAB-dependent properties may be the major contributor to short-term plasticity on the time scale of a few hundred milliseconds and are consistent with the hypothesis that the balance of different time-dependent processes can modulate the state of networks in a complex manner and could contribute to the generation of temporally sensitive neural responses.
MST Neurons Respond to Optic Flow and Translational Movement
Authors: Duffy Charles J.
Published: December 2017

Duffy, Charles J. MST neurons respond to optic flow and translational movement . J. Neurophysiol. 80: 1816–1827, 1998. We recorded the responses of 189 medial superior temporal area (MST) neurons by using optic flow, real translational movement, and combined stimuli in which matching directions of optic flow and real translational movement were presented together. One-half of the neurons (48%) showed strong responses to optic flow simulating self-movement in the horizontal plane, and 24% showed strong responses to translational movement. Combining optic flow stimuli with matching directions of translational movement caused substantial changes in both the amplitude of the best responses (44% of neurons) and the strength of direction selectivity (71% of neurons), with little effect on which stimulus direction was preferred. However, combining optic flow and translational movement such that opposite directions were presented together changed the preferred direction in 45% of the neurons with substantial changes in the strength of direction selectivity. These studies suggest that MST neurons combine visual and vestibular signals to enhance self-movement detection and disambiguate optic flow that results from either self-movement or the movement of large objects near the observer.
Multiple Cell Types Distinguished by Physiological, Pharmacological, and Anatomic Properties in Nucleus HVc of the Adult Zebra Finch
Authors: Dutar Patrick , Vu Huan M. , Perkel David J.
Published: December 2017

Dutar, Patrick, Huan M. Vu, and David J. Perkel. Multiple cell types distinguished by physiological, pharmacological, and anatomic properties in nucleus HVc of the adult zebra finch. J. Neurophysiol. 80: 1828–1838, 1998. Nucleus HVc of the songbird is a distinct forebrain region that is essential for song production and shows selective responses to complex auditory stimuli. Two neuronal populations within HVc give rise to its efferent projections. One projection, to the robust nucleus of the archistriatum (RA), serves as the primary motor pathway for song production, and can also carry auditory information to RA. The other projection of HVc begins a pathway through the anterior forebrain, (area X → medial portion of the dorsolateral nucleus of the thalamus (DLM) → lateral portion of the magnocellular nucleus of the anterior neostriatum (L-MAN) → RA) that is crucial for song learning but, although active during singing, is not essential for adult song production. To test whether these different projection neuron classes have different functional properties, we recorded intracellularly from neurons in nucleus HVc in brain slices. We observed at least three classes of neuron based on intrinsic physiological and pharmacological properties as well as on synaptic inputs. We also examined the morphological properties of the cells by filling recorded neurons with neurobiotin. The different physiological cell types correspond to separate populations based on their soma size, dendritic extent, and axonal projection. Thus HVc neurons projecting to area X have large somata, show little spike-frequency adaptation, a hyperpolarizing response to the metabotropic glutamate receptor (mGluR) agonist (1 S,3 R)- trans-1-aminocyclopentane-1,3-dicarboxylic acid (ACPD), and exhibit a slow inhibitory postsynaptic potential (IPSP) following tetanic stimulation. Those HVc neurons projecting to motor nucleus RA have smaller somata, show strong accommodation, are not consistently hyperpolarized by ACPD, and exhibit no slow IPSP. A third, rarely recorded class of neurons fire in a sustained fashion at very high-frequency and may be interneurons. Thus the neuronal classes within HVc have different functional properties, which may be important for carrying specific information to their postsynaptic targets.
Sour Transduction Involves Activation of NPPB-Sensitive Conductance in Mouse Taste Cells
Authors: Miyamoto Takenori , Fujiyama Rie , Okada Yukio , Sato Toshihide
Published: December 2017

Miyamoto, Takenori, Rie Fujiyama, Yukio Okada, and Toshihide Sato. Sour transduction involves activation of NPPB-sensitive conductance in mouse taste cells. J. Neurophysiol. 80: 1852–1859, 1998. We examined the sour taste transduction mechanism in the mouse by applying whole cell patch-clamp technique to nondissociated taste cells from the fungiform papillae. Localized stimulation with 0.5 M NaCl and 25 mM citric acid (pH 3.0) of the apical membrane enabled us to obtain responses from single taste cells under a quasi-natural condition. Of 28 taste cells examined, 11 cells (39%) responded to 0.5 M NaCl alone and 2 cells (7%) responded to 25 mM citric acid alone, indicating the presence of salty- and sour-specific taste cells. Ten cells (36%) responded to both NaCl and citric acid and 5 cells (18%) responded to neither salt nor citric acid. Amiloride reversibly suppressed NaCl-induced responses in mouse taste cells but not citric acid-induced responses. On the other hand, a Cl−channel blocker, 5-nitro-2-(3-phenylpropylamino)-benzoic acid (NPPB), reversibly suppressed all the citric-acid-induced responses. Most of the NaCl-induced current responses displayed an inwardly rectifying property, whereas all the citric-acid-induced responses displayed an outwardly rectifying property. The reversal potential for NPPB-sensitive component in citric-acid-induced current responses was −2 ± 7 mV (mean ± SE, n = 4), which was close to the equilibrium potential of Cl−( ECl), whereas the reversal potential for NPPB-insensitive component was 34 ± 8 mV ( n = 4). The reversal potential of citric-acid-induced current responses (19 ± 8 mV, n = 4) was mostly present at the middle point between reversal potentials of NPPB-sensitive and -insensitive current components. In some taste cells, an inorganic cation channel blocker, Cd2+, suppressed citric-acid-induced responses, but an inorganic stretch-activated cation channel blocker, Gd3+, did not affect these responses. These results suggest that salt- and acid-induced responses were mediated by differential transduction mechanisms in mouse taste cells and that NPPB-sensitive Cl−channels play a more important role to sour taste transduction rather than amiloride-sensitive Na+channels. However, the fact that the reversal potentials of citric-acid-induced responses had more positive than EClsuggests that Ca2+or H+permeable and poorly selective cation channels, which should be amiloride insensitive, may be activated by citric acid.
Muscle Activation Patterns During Two Types of Voluntary Single-Joint Movement
Authors: Gottlieb Gerald L.
Published: December 2017

Gottlieb, Gerald L. Muscle activation patterns during two types of voluntary single-joint movement. J. Neurophysiol. 80: 1860–1867, 1998. We examined the systematic variations in the EMG patterns during two types of single joint elbow movements. These patterns may be interpreted as exhibiting rules by which the CNS controls movement parameters. Normal human subjects performed two series of fast elbow flexion movements of 20–100° in a horizontal plane manipulandum. The first series consisted of pointing movements (PMs) from an initial position to a target; the second series consisted of reversal movements (RMs) to the same targets with an immediate return to the starting position. Both series showed kinematic and electromyographic (EMG) patterns that followed our previously described speed-insensitive strategy for controlling movement distance. Kinematic patterns of PMs and RMs were identical to about the time of peak PM deceleration. Agonist EMG bursts were also initially the same, but RM bursts ended abruptly in a silent period, whereas PM bursts declined more gradually. Antagonist EMG bursts of RMs were later than those of PMs but were not larger, contrary to our prior expectation and despite the larger net extension torque during RMs. The increase in net RM extension-directed torque that takes the limb back to its initial position appears to be a consequence of reduced flexor muscle torque rather than increased extensor muscle torque. We propose that rules for movement control may be similar for different kinds of movements as long as they are functionally sufficient for the task. However, even in a single-joint movement paradigm, physics alone, that is, the knowledge of net muscle torque and limb kinematics, is not adequate to fully predict those rules or the muscle activation patterns they produce. These must be discovered by experiment. The simplest expression of such rules may not be in terms of torque or kinematic variables but rather explicitly in terms of muscle activation patterns.
onandoffChannels of the Frog Optic Tectum Revealed by Current Source Density Analysis
Authors: Nakagawa Hideki , Matsumoto Nobuyoshi
Published: December 2017

Nakagawa, Hideki and Nobuyoshi Matsumoto. on and off channels of the frog optic tectum revealed by current source density analysis. J. Neurophysiol. 80: 1886–1899, 1998. The spatiotemporal patterns of excitatory synaptic activity in response to diffuse light on and off stimuli were examined by means of current source density (CSD) analysis. The qualitative and quantitative analyses obtained from 24 depth profiles for each stimulus revealed obviously different distributions of synaptic activity in the laminar structure. Two or three dominant current sinks I, II, and III were evoked in response to diffuse light on stimulation. Sink I was observed at the bottom of the retinorecipient layer. Both sinks II and III, showing an identical spatial pattern, were observed just above sink I. On the other hand, diffuse light off stimulation elicited up to six current sinks IV, V, VI, VII, VIII, and IX. Sink IV was observed at the bottom of the retinorecipient layer. Sink V was observed in the most superficial layer. Both sinks VI and VIII were located between the two preceding sinks. Finally, sinks VII and IX occurred below the retinorecipient layer. Five electrically evoked current sinks A, B, C, D, and E, characterized in our previous study, were also recognized in the present quantitative analysis. A statistical analysis revealed that, in visually evoked responses, statistical differences in the spatial distribution were not present between sinks I and IV, and sinks II and VIII ( P < 0.05). The analysis also showed that, in electrically evoked responses, only a pair of sinks C and E exhibit virtually identical spatial distribution ( P < 0.05). Based on well-known properties of the retinal ganglion cells, possible neuronal mechanisms underlying each of current sinks in the on and off channels and their functional meanings were considered. Sink I reflects the excitatory monosynaptic activity derived from R3 retinal ganglion cells. Sink IV reflects the excitatory monosynaptic activity derived from both R3 and R4 cells. Sinks V, VI, VII, and IX may be composed of successive polysynaptic excitatory potentials derived from convergence of inputs from both R3 and R4 cells. We concluded that the early four sinks play in particular an important role in eliciting avoidance behavior. On the other hand, sinks II, III, and VIII reflect excitatory synaptic activities derived from on-off retinal fibers of another type having slow conduction velocity. These late current sinks were suggested to mediate prey catching and its facilitation.