bluuebunny/crossref_metadata_2025 huggingface dataset:
Functionally defined smooth and saccadic eye movement subregions in the frontal eye field of Cebus monkeys
Authors: Tian J. R. , Lynch J. C.
Published: December 2017

1. Intracortical microstimulation was used to localize and define the smooth and saccadic eye movement subregions of the frontal eye field (FEF) and the supplementary eye field (SEF) in nine hemispheres of six Cebus apella monkeys and to map the hand/arm areas in the dorsal premotor area and other adjacent areas in five hemispheres of three C. apella monkeys. Monkeys were anesthetized during experiments with Telazol, a dissociative agent that has no significant effect on microstimulation-induced eye movement parameters (current threshold, velocity, and duration). The functional subregions were defined with the use of low threshold current (< or = 50 microA). Electrically elicited eye movements were videotaped and quantified. The two types of eye movements were clearly distinguished by their significantly different duration and velocity (P < 0.0001) and their different responses to long stimulus trains. 2. The saccadic subregion of the FEF in Cebus monkeys is in the same location as in macaque monkeys (Walker's areas 8a and 45). Most of the functional and anatomic characteristics of the saccadic subregion of Cebus are the same as those reported in the saccadic FEF subregion of macaque monkeys. 3. A subregion in which only smooth eye movements were evoked was found in the posterior shoulder of the superior arcuate sulcus near its medial tip. A band of inexcitable cortex separated the SEF and this smooth eye movement subregion of the FEF. This supports the proposal that the smooth eye movement subregion is independent of the SEF but is analogous to the saccadic subregion of the FEF. The existence of two subregions of the FEF was further confirmed by single-unit recording results. It is proposed that the smooth eye movement subregion in Cebus monkeys may be comparable with the one described in macaque monkeys. 4. Both saccadic and smooth eye movements were also reliably evoked in the SEF in each hemisphere studied. This result strongly indicates that the SEF is concerned with not only saccadic eye movements, as previously reported, but also with smooth (pursuit) eye movements.
Release of fixation for pursuit and saccades in humans: evidence for shared inputs acting on different neural substrates
Authors: Krauzlis R. J. , Miles F. A.
Published: December 2017

1. In three human subjects, we measured the latency of pursuit and saccadic eye movements made to an eccentric target after a fixated central target was extinguished. In one set of experiments, we varied the time interval between the extinction of the central target and the appearance of the eccentric target (“gap duration”). In a second set of experiments, we varied the eccentricity at which the second target appeared. 2. Varying the gap duration produced similar changes in the latencies of pursuit and saccades. Gaps as short as 30 ms caused significant decreases in latency; progressively longer gaps produced shorter latencies, reaching a minimum for gaps of 150–200 ms. Over the range of gap durations used, the latencies of pursuit and saccades displayed the same dependence on gap duration. 3. Varying the eccentricity of the second target produced different effects on the latencies of pursuit and saccades. Saccade latencies increased when the eccentricity of the second target was decreased from 4 degrees to 0.5 degree, whereas pursuit latencies were not consistently altered. Despite these differences in the dependence on retinal eccentricity between pursuit and saccades, imposing a 200-ms gap between the extinction of the fixation point and appearance of the second target still reduced the latency of both. 4. Our results are consistent with the idea that the mechanisms underlying the release of fixation for pursuit and saccades have shared inputs but a different neural substrate. The common dependence on gap duration may indicate that a single preparatory input coordinates both types of movements. The different dependence on retinal eccentricity indicates that there are differences in the spatial organization of the premotor circuits that trigger the onset of the two types of movements.
Light enhances hydrodynamic signaling in the multimodal caudal photoreceptor interneurons of the crayfish
Authors: Pei X. , Wilkens L. A. , Moss F.
Published: December 2017

1. The caudal photoreceptor (CPR) interneurons in the sixth abdominal ganglion of the crayfish are complex, multi-modal interneurons. These cells respond directly to light with tonic spike discharges, and they integrate synaptic input from an array of fili-form mechanoreceptors on the tailfan. They also provide input to rostral command centers, inducing backward walking at high firing frequencies, and thus directly influence behavior. 2. We recorded CPR activity in response to weak hydrodynamic stimulation of the tailfan mechanoreceptors while under varying intensities of light shined on the sixth ganglion. Spike trains were characterized according to the mean discharge rate (MDR) and the power spectrum from which the signal-to-noise ratio (SNR) was calculated. 3. Illumination of the CPR enhances the efficiency of transmitting mechanosensory signals. It does so by increasing the SNR of mechanosensory input received from tailfan receptors. A sevenfold, nonlinear increase in the SNRs was observed with increasing light intensity, an effect especially pronounced for weak hydrodynamic stimuli. In comparison with the dark, illumination of the ganglion lowered the hydrodynamic threshold and heightened the response to suprathreshold stimulation. Unlike the SNR, the MDR is little affected by mechanosensory input. 4. These results are compared with simulated electronic activity from an analogue threshold model and are discussed with respect to the mechanism of stochastic resonance.
Developmental dissociation of excitability and secretory ability in Aplysia bag cell neurons
Authors: Nick T. A. , Moreira J. E. , Kaczmarek L. K. , Carew T. J. , Wayne N. L.
Published: December 2017

1. Despite the considerable progress made in understanding the role of electrical activity in triggering secretion, the developmental relationships between excitability and secretion are not well understood. The well-characterized bag cell neurons of Aplysia provide an advantageous system in which to investigate developmental interactions of these two key properties of neurons. 2. A prolonged afterdischarge triggers egg laying hormone (ELH) secretion in mature bag cell neurons. To investigate secretion in the developmental framework of excitability, we first examined whether immature neurons, which are incapable of the mature form of excitability (afterdischarge), contain ELH and whether this hormone is packaged in vesicles. We used immunoelectron microscopy to compare vesicular localization of ELH and to compare the size and density of ELH-containing vesicles in neurons from adult and juvenile Aplysia. This comparison revealed that immature neurons contain ELH in vesicles in the size range of secretory vesicles. However, they lack a class of large vesicles (> 250 nm in diameter) that is characteristic of mature neurons. 3. To investigate whether the ELH contained in immature bag cell neurons could be secreted in response to electrical activity, we used the potassium channel blocker tetraethylammonium (TEA) combined with nerve stimulation to depolarize neurons from both juvenile animals (ovotestes do not contain eggs) and from adult Aplysia (ovotestes contain eggs). Using radioimmunoassay, we have found that the duration and amount of ELH secreted from bag cell neurons from juvenile Aplysia in response to TEA does not depend on whether or not the cells can be induced to afterdischarge, and the amount and duration of ELH secreted from bag cell neurons of juvenile Aplysia (whether or not they afterdischarged) differed from those secreted by adult neurons. However, by normalizing for body size, we found that the final estimated hemolymph concentration of ELH would be similar in juvenile and adult animals. 4. We investigated the potential functional significance of secretion of bag cell hormones in juvenile Aplysia by attempting to bypass the bag cell neurons and directly activate downstream elements with extract from adult bag cell neurons (BCE), known to contain ELH and other peptides. We found that juvenile Aplysia exhibit at least one component of egg-laying behavior, cessation of locomotion, in response to BCE during a developmental period (as measured by weight) in which they normally would possess neurons incapable of afterdischarge. Thus developmental regulation of excitability in the bag cell neurons may prevent inappropriate hormone release and subsequent premature expression of reproductive behaviors.
Functional changes in sodium conductances in the human neuroblastoma cell line SH-SY5Y during in vitro differentiation
Authors: Toselli M. , Tosetti P. , Taglietti V.
Published: December 2017

1. The electrophysiological properties of voltage-dependent sodium currents were studied in the human neuroblastoma cell line SH-SY5Y before and after in vitro differentiation with retinoic acid, with the use of the whole cell variant of the patch-clamp technique. 2. Voltage steps from a holding level of -90 mV to depolarizing potentials elicited, in both undifferentiated and differentiated cells, fast inward sodium currents that were full inactivating and tetrodotoxin sensitive. 3. In undifferentiated cells the current peaked at -10 mV, the half-activation potential was -35 mV, and the half-inactivation potential was -81 mV. In differentiated cells the current peaked at + 10 mV, the half-activation potential was -28 mV, and the half-inactivation potential was -56 mV. Moreover, the peak current amplitude was about a factor of 2 larger and inactivation kinetics was about a factor of 2 slower than in undifferentiated cells. 4. This diversity in sodium channel properties was related to differences in cell excitability. Under current-clamp conditions, intracellular injection of rectangular depolarizing current stimuli from a hyperpolarized membrane potential of about -100 mV elicited graded and weak regenerative responses in undifferentiated cells, whereas overshooting action potentials with faster rising phases could be elicited in differentiated cells.
Neural Mechanisms of Spatial Selective Attention in Areas V1, V2, and V4 of Macaque Visual Cortex
Authors: Luck Steven J. , Chelazzi Leonardo , Hillyard Steven A. , Desimone Robert
Published: December 2017

Luck, Steven J., Leonardo Chelazzi, Steven A. Hillyard, and Robert Desimone. Neural mechanisms of spatial selective attention in areas V1, V2, and V4 of macaque visual cortex. J. Neurophysiol. 77: 24–42, 1997. Many neurons in extrastriate visual cortex have large receptive fields, and this may lead to significant computational problems whenever multiple stimuli fall within a single field. Previous studies have suggested that when multiple stimuli fall within a cell's receptive field, they compete for the cell's response in a manner that can be biased in favor of attended stimuli. In the present study we examined this role of attention in areas V1, V2, and V4 of macaque monkeys with the use of a behavioral paradigm in which attention was directed to one of two stimulus locations. When two stimuli were presented simultaneously inside the cell's receptive field (which could be accomplished only in areas V2 and V4), we found that the cell's response was strongly influenced by which of the two stimuli was attended. The size of this attention effect was reduced when the attended and ignored stimuli were presented sequentially rather than simultaneously. In addition, the effects became very weak and inconsistent in these areas when only one of the two stimuli was located inside the receptive field. Attention thus modulated sensory responses primarily when two or more simultaneous stimuli competed for access to a neuron's receptive field. As in areas V2 and V4, attention did not modulate sensory responses in area V1 when only a single stimulus was inside the receptive field. In addition, the small receptive fields in this area precluded the simultaneous presentation of attended and ignored stimuli inside the receptive field, making it impossible to determine whether attention effects would be observed under the conditions that led to consistent attention effects in areas V2 and V4. Spontaneous firing rates in areas V2 and V4 were found to be 30–40% higher when attention was directed inside rather than outside the receptive field, even when no stimulus was present in the receptive field. Spontaneous firing rates also varied according to the particular location within the receptive field that was attended. These shifts in spontaneous activity may reflect a top-down signal that biases responses in favor of stimuli at the attended location.
Dissociation of Visual Discrimination From Saccade Programming in Macaque Frontal Eye Field
Authors: Thompson Kirk G. , Bichot Narcisse P. , Schall Jeffrey D.
Published: December 2017

Thompson, Kirk G., Narcisse P. Bichot, and Jeffrey D. Schall. Dissociation of visual discrimination from saccade programming in macaque frontal eye field. J. Neurophysiol. 77: 1046–1050, 1997. To determine whether visual discrimination in macaque frontal eye field (FEF) is contingent on saccade planning, unit activity was recorded in two monkeys during blocked go and no-go visual search trials. The eye movements made by monkeys after correct no-go trials, in addition to an attenuation of the visual responses in no-go trials compared with go trials, indicated that covert saccade planning was effectively discouraged. During no-go search trials, the activity of the majority of neurons evolved to signal the location of the oddball stimulus. The degree and time course of the stimulus discrimination process observed in no-go trials was not different from that observed in go trials. We conclude that the discrimination of a salient visual stimulus reflected by FEF neurons is not contingent on saccade production but rather may reflect the outcome of an automatic visual selection process.
Functional Double Dissociation Between Two Inferior Temporal Cortical Areas: Perirhinal Cortex Versus Middle Temporal Gyrus
Authors: Buckley M. J. , Gaffan D. , Murray E. A.
Published: December 2017

Buckley, M. J., D. Gaffan, and E. A. Murray. Functional double dissociation between two inferior temporal cortical areas: perirhinal cortex versus middle temporal gyrus. J. Neurophysiol. 77: 587–598, 1997. There is both anatomic and cytoarchitectural evidence for dorsal-ventral subdivisions of the inferior temporal cortex. Despite this, there has been only limited evidence of corresponding functional subdivisions and no evidence that two adjacent cortical areas within the inferior temporal cortex, namely area TE and the perirhinal cortex, have distinctly different roles in vision and memory. We assessed the color discrimination abilities of cynomolgus monkeys with either bilateral ablation of the perirhinal cortex or bilateral ablation of the middle temporal gyrus. The stimuli were isoluminant colored squares presented on a touch screen. In each trial the subject had to learn to discriminate and select the correct choice (green) from among a maximum of eight other foils, each varying in either hue or saturation. Relative to unoperated controls, monkeys with middle temporal gyrus lesions were severely impaired in the color discrimination task, whereas monkeys with perirhinal lesions were unimpaired on this task. We also assessed the visual recognition abilities, as measured by a basic delayed nonmatching-to-sample task with trial-unique objects presented in a Wisconsin General Test Apparatus, of rhesus monkeys with bilateral middle temporal gyrus lesions. We then tested the monkeys' postoperative performance on a delayed nonmatching-to-sample task with delays and extended list lengths. The results from this experiment were compared with those from two other groups of rhesus monkeys, an unoperated control group and a group with bilateral perirhinal cortex lesions, both of which had performed the identical tasks in a previous experiment. Relative to unoperated controls, monkeys with perirhinal cortex lesions were severely impaired both in relearning the basic delayed nonmatching-to-sample task and on the postoperative performance test. In contrast, monkeys with middle temporal gyrus lesions were only mildly affected in relearning the basic nonmatching task and were unimpaired on the postoperative performance test. Thus our data demonstrate a clear functional double dissociation between the perirhinal cortex and the middle temporal gyrus. This result gives strong support to the hypothesis that the perirhinal cortex and the adjacent area TE have distinctly different roles in visual learning and memory.
Inhibition of the Electrogenic Na Pump Underlies Delayed Depolarization of Cortical Neurons After Mechanical Injury or Glutamate
Authors: Tavalin Steven J. , Ellis Earl F. , Satin Leslie S.
Published: December 2017

Tavalin, Steven J., Earl. F. Ellis, and Leslie S. Satin. Inhibition of the electrogenic Na pump underlies delayed depolarization of cortical neurons after mechanical injury or glutamate. J. Neurophysiol. 77: 632–638, 1997. We previously characterized the electrophysiological response of cortical neurons to a brief sublethal stretch-injury using an in vitro model of traumatic brain injury. This model revealed that cortical neurons undergo a stretch-induced delayed depolarization (SIDD) of their resting membrane potential (RMP) which is ∼10 mV in magnitude. SIDD is dependent on N-methyl-d-aspartate (NMDA) receptor activation, neuronal firing, and extracellular calcium for its induction but not its maintenance. SIDD was maximal 1 h after the insult and required incubation at 37°C. The present study examined the mechanism mediating SIDD and its relation to glutamate receptor activation. The Na pump inhibitor ouabain was used to assess the contribution of the Na pump to the RMP of control and stretched neurons using whole cell patch-clamp techniques. The nitric oxide (NO) synthase inhibitor Nω-nitro-L-arginine and a polyethylene glycol conjugate of superoxide dismutase were used to assess whether NO or superoxide anion, respectively, were involved in the induction of SIDD. Neurons were exposed to exogenous glutamate in the absence of cell stretch to determine whether glutamate alone can mimic SIDD. We report that SIDD is mediated by Na pump inhibition and is likely to result from reduced energy levels since the RMP of neurons dialyzed with a pipette solution containing 5 mM ATP were identical to controls. NO, but not superoxide anion, also may contribute to SIDD. A 3-min exposure to 10 μM glutamate produced a SIDD-like depolarization also associated with Na pump inhibition. The results suggest that Na pump inhibition secondary to alterations in cellular energetics underlies SIDD. Na pump inhibition due to glutamate exposure may contribute to traumatic brain injury or neurodegenerative diseases linked to glutamate receptor activation.
Planar Directional Contributions to Optic Flow Responses in MST Neurons
Authors: Duffy Charles J. , Wurtz Robert H.
Published: December 2017

Duffy, Charles J. and Robert H. Wurtz. Planar directional contributions to optic flow responses in MST neurons. J. Neurophysiol. 77: 782–796, 1997. Many neurons in the dorsal region of the medial superior temporal area (MSTd) of monkey cerebral cortex respond to optic flow stimuli in which the center of motion is shifted off the center of the visual field. Each shifted-center-of-motion stimulus presents both different directions of planar motion throughout the visual field and a unique pattern of global motion across the visual field. We investigated the contribution of planar motion to the responses of these neurons in two experiments. In the first, we compared the responses of 243 neurons to planar motion and to shifted-center-of-motion stimuli created by vector summation of planar motion and radial or circular motion. We found that many neurons preferred the same directions of motion in the combined stimuli as in the planar stimuli, but other neurons did not. When we divided our sample into one group with stronger directionality to both planar and vector combination stimuli and one group with weaker directionality, we found that the neurons with the stronger directionality were those that showed the greatest similarity in the preferred direction of motion for both the planar and combined stimuli. In a second set of experiments, we overlapped planar motion and radial or circular motion to create transparent stimuli with the same motion components as the vector combination stimuli, but without the shifted centers of motion. We found that the neurons that responded most strongly to the planar motion when it was combined with radial or circular motion also responded best when the planar motion was overlapped by a transparent motion stimulus. We conclude that the responses of those neurons with stronger directional responses to both the motion of planar and vector combination stimuli are most readily understood as responding to the total planar motion in the stimulus, a planar motion mechanism. Other neurons that had weaker directional responses showed no such similarity in the preferred directions of planar motion in the vector combination and the transparent overlap stimuli and fit best with a mechanism dependent on the global motion pattern. We also found that neurons having significant responses to both radial and circular motion also responded to the spiral stimuli that result from a vector combination of radial and circular motion. The preferred planar-spiral vector combination stimulus was frequently the one containing that neurons' preferred direction of planar motion, which makes them similar to other MSTd neurons.
Heterogeneity of Electrically Evoked Dopamine Release and Reuptake in Substantia Nigra, Ventral Tegmental Area, and Striatum
Authors: Cragg S. J. , Rice M. E. , Greenfield S. A.
Published: December 2017

Cragg, S. J., M. E. Rice, and S. A. Greenfield. Heterogeneity of electrically evoked dopamine release and reuptake in substantia nigra, ventral tegmental area, and striatum. J. Neurophysiol. 77: 863–873, 1997. Somatodendritic dopamine (DA) released in substantia nigra pars compacta (SNc) and the ventral tegmental area (VTA) may mediate extrasynaptic neuronal signaling. The concentration of extracellular DA ([DA]o) attained during somatodendritic activation will be governed by the density of release sites and properties of DA uptake. We evaluated these factors in SNc, VTA, and dorsal striatum with carbon-fiber microelectrodes and fast-scan cyclic voltammetry to monitor [DA]o during local electrical stimulation (10 Hz, 5 s) in guinea pig brain slices. Stimulated DA efflux was site specific, with significantly higher [DA]o in caudal (0.48 ± 0.03 μM, mean ± SE) than rostral SNc (0.16 ± 0.01 μM), averaged over their mediolateral extents, and higher [DA]o in VTA (0.74 ± 0.07 μM) than in medial (0.43 ± 0.04 μM) or lateral SNc (0.29 ± 0.05 μM), averaged rostrocaudally. Throughout SNc, evoked [DA]o correlated positively ( r = 0.91) with the density of tyrosine-hydroxylase-immunoreactive cells. Modulation of evoked [DA]o by uptake was also site specific. The selective DA uptake inhibitor GBR 12909 significantly increased evoked [DA]o in caudal SNc (to 185 ± 27%) and striatum (408 ± 24%), but had no effect in rostral SNc or VTA. Conversely, the norepinephrine (NE) uptake inhibitor desipramine did not alter stimulated [DA]o in caudal SNc or striatum, but caused significant enhancement in rostral SNc (196 ± 17%) and VTA (126 ± 12%). Paroxetine, a selective 5-hydroxytryptamine uptake inhibitor, had little effect in any region tested. Site-specific sensitivity to desipramine mandated evaluation of dopamine-β-hydroxylase immunoreactivity (DβH-ir) in midbrain. The density of filaments positive for DβH-ir was greater in rostral SNc and VTA than in caudal SNc, suggesting DA clearance via the NE transporter in these regions. Importantly, DβH-ir was most dense in sections rostral to SNc where no catecholamine signal was detected and no enhancement was observed with desipramine, indicating a lack of NE contribution to evoked release in any region examined. Taken together, these data confirmed that evoked somatodendritic [DA]o depends on DA cell density and on local uptake properties. Uptake was less efficient in SNc and VTA than in striatum. Moreover, enhancement of stimulated [DA]o by GBR 12909 demonstrated that evoked release from dendrites is not via reversal of the DA transporter. Lastly, the heterogeneous patterns of DA uptake within SNc and VTA were consistent with the pattern of degeneration in Parkinson's disease: less vulnerable DA cells, e.g., those in VTA, have less DA uptake than the more vulnerable cells of caudal SNc.
Primate Sense of Taste: Behavioral and Single Chorda Tympani and Glossopharyngeal Nerve Fiber Recordings in the Rhesus Monkey, Macaca mulatta
Authors: Hellekant Göran , Danilova Vicktoria , Ninomiya Yuzo
Published: December 2017

Hellekant, Göran, Vicktoria Danilova, and Yuzo Ninomiya. Primate sense of taste: behavioral and single chorda tympani and glossopharyngeal nerve fiber recordings in the rhesus monkey, Macaca mulatta. J. Neurophysiol. 77: 978–993, 1997. The responses of 51 chorda tympani proper (CT) and 33 glossopharyngeal (NG) neural taste units from the rhesus monkey ( Macaca mulatta) were recorded during stimulation of either the anterior (CT) or posterior (NG) part of the tongue with 26 stimuli that taste salty, umami, sour, bitter, and sweet to humans. In the CT, hierarchical cluster analysis separated four major clusters. The N and S clusters were most populous, followed by the H cluster and a small Q cluster. NaCl, monosodium glutamate (MSG), and MSG with guanosine 5′-monophosphate were the best stimuli in the N cluster. Amiloride suppressed responses to NaCl. KCl did not stimulate fibers from this cluster. S cluster fibers were characterized by strong responses to all sweeteners. The H cluster responded best to acids but also to some of the sweeteners such as xylitol, fructose, and sucrose. Q fibers responded well to quinine hydrochloride (QHCl) and caffeine, but not to denatonium benzoate. In the NG, hierarchical cluster analysis separated three major clusters. Q fibers formed the largest cluster. QHCl, caffeine, and sucrose octa-acetate but not denatonium benzoate elicited very strong responses in these fibers. S fibers formed a second cluster. Although most of the sweeteners stimulated the S fibers, their responses were not so pronounced as in CT S fibers. The small M cluster was formed by fibers that responded best to MSG. They also responded to NaCl and acids. Two bottle preference tests showed a positive relationship between a sweetener's ability to stimulate the taste fibers and the animals' consumption. Thus the most-liked sweeteners stimulated the S cluster fibers of CT best, whereas less-liked sweeteners such as d-phenylalanine elicited a response in Q fibers and sodium cyclamate stimulated N fibers. The results show that both CT and NG taste fibers of M. mulatta group according to the human concepts of taste qualities.
Pallidal Discharge Related to the Kinematics of Reaching Movements in Two Dimensions
Authors: Turner Robert S. , Anderson Marjorie E.
Published: December 2017

Turner, Robert S. and Marjorie E. Anderson. Pallidal discharge related to the kinematics of reaching movements in two dimensions. J. Neurophysiol. 77: 1051–1074, 1997. Movement-related discharge of neurons in the internal and external segments of the globus pallidus (GPi and GPe, respectively) of two monkeys was studied during reaching movements in a two-dimensional workspace. Discharge was studied during movements to targets in eight directions and at three distances from the starting position under three behavioral conditions that manipulated target visibility and movement triggering. A total of 73 neurons (57 in GPe and 18 in GPi) with changes in discharge in concert with arm movements were included in a quantitative analysis. Of these, 83% also changed their discharge during manipulation of the contralateral arm outside of the task. Although 73% of changes in discharge began before the initiation of movement, they seldom preceded the initial activity of the agonist muscles. Decreases in discharge were more common than reported previously, constituting 40% of the changes in discharge detected. In GPi neurons, decreases also tended to begin earlier than increases. Changes in discharge in GPe neurons were of larger magnitude than those in GPi, and increases in discharge were larger than decreases. Onsets of changes in discharge were temporally linked to movement onset in 69% of neurons. Time locking of neural onsets to trigger presentation and movement termination was found in only 30 and 1% of neurons,respectively. Direction of movement influenced the magnitude of changes in discharge in 78% of cells. Directional modulations were broadly tuned and preferred directions were uniformly distributed across the range of directions. When directional modulations were large, preferred directions were consistent for different amplitudes of movement and for different behavioral conditions. Amplitude of movement influenced the magnitude of changes in discharge in 78% of cells, and in 80% of cases that relation had a significant linear component. Amplitude effects were not more common or stronger for movements in directions close to a cell's preferred direction. Linear relations to movement amplitude were more common and accounted for more of the trial-to-trial variance in discharge rate than relations to either average velocity or movement duration. The relation to movement amplitude was consistent for two behavioral conditions when the change in discharge was scaled strongly with movement amplitude. Movement-related changes in discharge of neurons in the skeletomotor portions of both pallidal segments reflect the kinematics of movement. This information, encoded in combination with sensory and contextual information, may play an on-line role in the selective facilitation and suppression of different frontal thalamocortical circuits.
Low-Affinity Kainate Receptors and Long-Lasting Depression of NMDA-Receptor–Mediated Currents in Rat Superficial Dorsal Horn
Authors: Sequeira Sandra , Näsström Jacques
Published: December 2017

Sequeira, Sandra and Jacques Näsström. Low-affinity kainate receptors and long-lasting depression of NMDA-receptor–mediated currents in rat superficial dorsal horn. J. Neurophysiol. 80: 895–902, 1998. In an in vitro spinal cord slice preparation whole cell electrophysiological recordings of rat superficial dorsal horn neurons responding differentially to glutamate (Glu) and N-methyl-d-aspartate (NMDA) were investigated systematically for the role of kainate (KA) receptors in modulating their activity. In these neurons, coapplication of Glu and NMDA, as well as application of Glu immediately before NMDA, induced long- and short-lasting depressions of NMDA-induced currents as well as depression of NMDA-receptor–mediated excitatory postsynaptic currents. KA applied before NMDA mimicked Glu-induced attenuating effects. Furthermore, the low-affinity KA receptor antagonist 5-nitro-6,7,8,9- tetrahydrobenzo[G]indole-2,3-dione-3-oxime potentiated Glu-induced NMDA-receptor–mediated currents in neurons responding differentially to Glu and NMDA. These results provide evidence for a novel mechanism, which may relate to classical long-term depression, involving low-affinity KA receptors in long-lasting modulation of NMDA-receptor–mediated currents. This implies a physiological role of KA receptors in long-term modulation of sensory transmission in the superficial dorsal horn of rat spinal cord.
Electrophysiological Characteristics of Classes of Neuron in the HVc of the Zebra Finch
Authors: Kubota Michinori , Taniguchi Ikuo
Published: December 2017

Kubota, Michinori and Ikuo Taniguchi. Electrophysiological characteristics of classes of neuron in the HVc of the zebra finch. J. Neurophysiol. 80: 914–923, 1998. Whole cell recordings were made from zebra finch HVc neurons in slice preparations. Four distinct classes of neuron were found on the basis of their electrophysiological properties. The morphological characteristics of some of these neurons were also examined by intracellular injection of Lucifer yellow. Type I neurons (21 of 65 cells) had longer time-to-peak of an afterhyperpolarization following an action potential than the other classes. They exhibited both fast and time-dependent inward rectification and an initial high-frequency firing followed by a slower constant firing. Type I neurons had large somata and thick dendrites with many spines. The axons of some of the neurons in this class projected in the direction of area X of the parolfactory lobe. Type II neurons (30 of 65 cells) had a more negative resting membrane potential than the other classes. They exhibited fast inward rectification. Type II neurons could be divided into two subclasses by the absence (IIa; 22 cells) and the presence (IIb; 8 cells) of a low-threshold transient depolarization. Type IIa neurons had relatively small somata and thin, spiny dendrites. The axons of some of the neurons in this class projected in the direction of the robust nucleus of the archistriatum (RA). Type IIb neurons had relatively large somata and thick dendrites with many spines. Type III neurons (6 of 65 cells) had a shorter action-potential duration than the other classes. They exhibited prominent time-dependent inward rectification and a regular tonic firing with little or no accommodation. Type III neurons had beaded, aspiny dendrites. Type IV neurons (8 of 65 cells) had a longer action-potential duration, a much larger input resistance, and longer membrane time constant than the other classes. Type IV neurons had small somata and thin, short, sparsely spiny dendrites. The axons of some of the neurons in this class projected in the direction of the RA. These classes of neuron may play distinct roles in song production and representation in the HVc.
Modifications of Reward Expectation-Related Neuronal Activity During Learning in Primate Striatum
Authors: Tremblay Léon , Hollerman Jeffrey R. , Schultz Wolfram
Published: December 2017

Tremblay, Léon, Jeffrey R. Hollerman, and Wolfram Schultz. Modifications of reward expectation-related neuronal activity during learning in primate striatum. J. Neurophysiol. 80: 964–977, 1998. This study investigated neuronal activity in the anterior striatum while monkeys repeatedly learned to associate new instruction stimuli with known behavioral reactions and reinforcers. In a delayed go-nogo task with several trial types, an initial picture instructed the animal to execute or withhold a reaching movement and to expect a liquid reward or not. During learning, new instruction pictures were presented, and animals guessed and performed one of the trial types according to a trial-and-error strategy. Learning of a large number of pictures resulted in a learning set in which learning took place in a few trials and correct performance exceeded 80% in the first 60–90 trials. About 200 task-related striatal neurons studied in both familiar and learning conditions showed three forms of changes during learning. Activations related to the preparation and execution of behavioral reactions and the expectation of reward were maintained in many neurons but occurred in inappropriate trial types when behavioral errors were made. The activations became appropriate for individual trial types when the animals' behavior adapted to the new task contingencies. In particular, reward expectation-related activations occurred initially in both rewarded and unrewarded movement trials and became subsequently restricted to rewarded trials. These changes occurred in parallel with the visible adaptation of reward expectations by the animals. The second learning change consisted in decreases of task-related activations that were either restricted to the initial trials of new learning problems or persisted during the subsequent consolidation phase. They probably reflected reductions in the expectation and preparation of upcoming task events, including reward. The third learning change consisted in transient or sustained increases of activations. These might reflect the increased attention accompanying learning and serve to induce synaptic changes underlying the behavioral adaptations. Both decreases and increases often induced changes in the trial selective occurrence of activations. In conclusion, neurons in anterior striatum showed changes related to adaptations or reductions of expectations in new task situations and displayed activations that might serve to induce structural changes during learning.
Orphanin FQ/Nociceptin Inhibits Synaptic Transmission and Long-Term Potentiation in Rat Dentate Gyrus Through Postsynaptic Mechanisms
Authors: Yu Tzu-Ping , Xie Cui-Wei
Published: December 2017

Yu, Tzu-Ping and Cui-Wei Xie. Orphanin FQ/nociceptin inhibits synaptic transmission and long-term potentiation in the rat dentate gyrus through postsynaptic mechanisms. J. Neurophysiol. 80: 1277–1284, 1998. Orphanin FQ/nociceptin (OFQ), a recently characterized natural ligand for the opioid receptor-like 1 (ORL1) receptor, shares structural similarity to the endogenous opioids. Our previous study found that OFQ, like classical opioids, modulated synaptic transmission and long-term potentiation (LTP) in the hippocampal CA1 region, suggesting a modulatory role for OFQ in synaptic plasticity involved in learning and memory. In the present study we investigated the action of OFQ in the dentate gyrus and explored possible underlying cellular mechanisms. Field potential recordings showed that OFQ significantly inhibited excitatory synaptic transmission and LTP induction in the dentate lateral perforant path. In the presence of OFQ, the excitatory postsynaptic potential (EPSP) slope-population spike (E-S) curve was shifted to the right, and no significant change was found in paired-pulse facilitation, suggesting a postsynaptic mechanism responsible for the inhibition of synaptic transmission. Under whole cell voltage-clamp conditions, bath application of OFQ activated K+ currents in most granule cells tested at a holding potential of −50 mV, suggesting that OFQ could reduce the excitability of dentate granule cells by hyperpolarizing cell membranes. OFQ also inhibited the amplitude of N-methyl-d-aspartate (NMDA) receptor–mediated excitatory postsynaptic currents (EPSCs) without affecting α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor–mediated EPSCs. This inhibition was not blocked by opioid receptor antagonists. Furthermore, the inward currents evoked by focal application of NMDA to granule cells were suppressed by OFQ in a dose-dependent manner, suggesting that OFQ may suppress LTP by inhibiting the function of postsynaptic NMDA receptors. These results demonstrate that OFQ may negatively modulate synaptic transmission and plasticity in the dentate gyrus through postsynaptic mechanisms, including hyperpolarization of granule cells as well as inhibition of the function of postsynaptic NMDA receptors/channels in dentate granule cells.
Spike-Wave Complexes and Fast Components of Cortically Generated Seizures. I. Role of Neocortex and Thalamus
Authors: Steriade Mircea , Contreras Diego
Published: December 2017

Steriade, Mircea and Diego Contreras. Spike-wave complexes and fast components of cortically generated seizures. I. Role of neocortex and thalamus. J. Neurophysiol. 80: 1439–1455, 1998. We explored the relative contributions of cortical and thalamic neuronal networks in the generation of electrical seizures that include spike-wave (SW) and polyspike-wave (PSW) complexes. Seizures were induced by systemic or local cortical injections of bicuculline, a γ-aminobutyric acid-A (GABAA) antagonist, in cats under barbiturate anesthesia. Field potentials and extracellular neuronal discharges were recorded through arrays of eight tungsten electrodes (0.4 or 1 mm apart) placed over the cortical suprasylvian gyrus and within the thalamus. 1) Systemic injections of bicuculline induced SW/PSW seizures in cortex, whereas spindle sequences continued to be present in the thalamus. 2) Cortical suprasylvian injection of bicuculline induced focal paroxysmal single spikes that developed into full-blown seizures throughout the suprasylvian cortex. The seizures were characterized by highly synchronized SW or PSW complexes at 2–4 Hz, interspersed with runs of fast (10–15 Hz) activity. The intracellular aspects of this complex pattern in different types of neocortical neurons are described in the following paper. Complete decortication abolished the seizure, leaving intact thalamic spindles. Injections of bicuculline in the cortex of athalamic cats resulted in similar components as those occurring with an intact thalamus. 3) Injection of bicuculline in the thalamus decreased the frequency of barbiturate spindles and increased the synchrony of spike bursts fired by thalamocortical and thalamic reticular cells but did not induce seizures. Decortication did not modify the effects of bicuculline injection in the thalamus. Our results indicate that the minimal substrate that is necessary for the production of seizures consisting of SW/PSW complexes and runs of fast activity is the neocortex.
Oscillatory Activity in the Cerebellar Hemispheres of Unrestrained Rats
Authors: Hartmann Mitra J. , Bower James M.
Published: December 2017

Hartmann, Mitra J. and James M. Bower. Oscillatory activity in the cerebellar hemispheres of unrestrained rats. J. Neurophysiol. 80: 1598–1604, 1998. We recorded multiunit neural activity in the granule cell layer of cerebellar folium Crus IIa in unrestrained rats. Seven- to 8-Hz oscillatory activity was seen during behavioral states in which the animal was immobile; any movement the animal made coincided with termination of the oscillations. However, nearly one-third of oscillatory episodes appeared to cease spontaneously, in the absence of any observable sensory input or movement. Oscillations were synchronized both within and between cerebellar hemispheres, demonstrating precise temporal coordination among multiple, bilateral levels of the somatosensory system. We interpret these data in the context of similar oscillations observed in other brain structures and suggest that the oscillations are an underlying dynamic property of the entire somatosensory network.
State-Dependent Nickel Block of a High-Voltage–Activated Neuronal Calcium Channel
Authors: McFarlane Matthew B. , Gilly William F.
Published: December 2017

McFarlane, Matthew B. and William F. Gilly. State-dependent nickel block of a high-voltage–activated neuronal calcium channel. J. Neurophysiol. 80: 1678–1685, 1998. Effects of nickel ions (Ni2+) on noninactivating calcium channels in squid giant fiber lobe (GFL) neurons were investigated with whole cell voltage clamp. Three different effects of Ni2+ were observed to be associated with distinct Ca2+ channel activation states. 1) Nickel ions appear to stabilize closed channel states and, as a result, slow activation kinetics. 2) Nickel ions block open channels with little voltage dependence over a wide range of potentials. 3) Block of open channels by Ni2+ becomes more effective during an extended strong depolarization, and this effect is voltage dependent. Recovery from this additional inhibition occurs at intermediate voltages, consistent with the presence of two distinct types of Ni2+ block that we propose correspond to two previously identified open states of the calcium channel. These results, taken together with earlier evidence of state-dependent block by ω-agatoxin IVA, suggest that Ni2+ generates these unique effects in part by interacting differently with the external surface of the GFL calcium channel complex in ways that depend on channel activation state.
Long-Range Connections Synchronize Rather Than Spread Intrathalamic Oscillations: Computational Modeling and In Vitro Electrophysiology
Authors: Sohal Vikaas S. , Huguenard John R.
Published: December 2017

Sohal, Vikaas S. and John R. Huguenard. Long-range connections synchronize rather than spread intrathalamic oscillations: computational modeling and in vitro electrophysiology. J. Neurophysiol. 80: 1736–1751, 1998. A thalamic network model was developed based on recent data regarding heterogeneous thalamic reticular (RE) cell axonal arborizations that indicate at least two projection patterns, short-range cluster projections and long-range diffuse projections. The model was constrained based on expected convergence and the biophysical properties of RE and thalamocortical (TC) cells and their synapses. The model reproduced in vitro synchronous slow (3-Hz) oscillatory activity and the known effects of T-channel blockade and cholecystokinin (CCK) application on this activity. Whereas previous models used the speed at which ≈3-Hz oscillations propagate in vitro to infer the spatial extent of intrathalamic projections, we found that, so long as the γ-aminobutyric acid-B synaptic conductance was adjusted appropriately, a network with only short-range projections and another network with both short- and long-range projections could both produce physiologically realistic propagation speeds. Although the ≈3-Hz oscillations propagated at similar speeds in both networks, phase differences between oscillatory activity at different locations in the network were much smaller in the network containing both short- and long-range projections. We measured phase differences in vitro and found that they were similar to those that arise in the network containing both short- and long-range projections but are inconsistent with the much larger phase differences that occur in the network containing only short-range projections. These results suggest that, although they extend much further than do short-range cluster projections, long-range diffuse projections do not spread activity over greater distances or increase the speed at which intrathalamic oscillations propagate. Instead, diffuse projections may function to synchronize activity and minimize phase shifts across thalamic networks. One prediction of this hypothesis is that, immediately after a collision between propagating oscillations, phase gradients should vary smoothly across the thalamic slice. The model also predicts that phase shifts between oscillatory activity at different points along a thalamic slice should be unaffected by T-channel blockers and decreased by suppression of synaptic transmission or application of CCK.