bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms for Force Adjustments to Unpredictable Frictional Changes at Individual Digits During Two-Fingered Manipulation
Authors: Birznieks Ingvars , Burstedt Magnus K. O. , Edin Benoni B. , Johansson Roland S.
Published: December 2017

Birznieks, Ingvars, Magnus K. O. Burstedt, Benoni B. Edin, and Roland S. Johansson. Mechanisms for force adjustments to unpredictable frictional changes at individual digits during two-fingered manipulation. J. Neurophysiol. 80: 1989–2002, 1998. Previous studies on adaptation of fingertip forces to local friction at individual digit–object interfaces largely focused on static phases of manipulative tasks in which humans could rely on anticipatory control based on the friction in previous trials. Here we instead analyze mechanisms underlying this adaptation after unpredictable changes in local friction between consecutive trials. With the tips of the right index and middle fingers or the right and left index fingers, subjects restrained a manipulandum whose horizontal contact surfaces were located side by side. At unpredictable moments a tangential force was applied to the contact surfaces in the distal direction at 16 N/s to a plateau at 4 N. The subjects were free to use any combination of normal and tangential forces at the two fingers, but the sum of the tangential forces had to counterbalance the imposed load. The contact surface of the right index finger was fine-grained sandpaper, whereas that of the cooperating finger was changed between sandpaper and the more slippery rayon. The load increase automatically triggered normal force responses at both fingers. When a finger contacted rayon, subjects allowed slips to occur at this finger during the load force increase instead of elevating the normal force. These slips accounted for a partitioning of the load force between the digits that resulted in an adequate adjustment of the normal:tangential force ratios to the local friction at each digit. This mechanism required a fine control of the normal forces. Although the normal force at the more slippery surface had to be comparatively low to allow slippage, the normal forces applied by the nonslipping digit at the same time had to be high enough to prevent loss of the manipulandum. The frictional changes influenced the normal forces applied before the load ramp as well as the size of the triggered normal force responses similarly at both fingers, that is, with rayon at one contact surface the normal forces increased at both fingers. Thus to independently adapt fingertip forces to the local friction the normal forces were controlled at an interdigital level by using sensory information from both engaged digits. Furthermore, subjects used both short- and long-term anticipatory mechanisms in a manner consistent with the notion that the central nervous system (CNS) entertains internal models of relevant object and task properties during manipulation.
High Safety Factor for Action Potential Conduction Along Axons But Not Dendrites of Cultured Hippocampal and Cortical Neurons
Authors: Mackenzie Paul J. , Murphy Timothy H.
Published: December 2017

Mackenzie, Paul J. and Timothy H. Murphy. High safety factor for action potential conduction along axons but not dendrites of cultured hippocampal and cortical neurons. J. Neurophysiol. 80: 2089–2101, 1998. By using a combination of Ca2+imaging and current-clamp recording, we previously reported that action potential (AP) conduction is reliably observed from the soma to axonal terminals in cultured cortical neurons. To extend these studies, we evaluated Ca2+influx evoked by Na+APs as a marker of AP conduction under conditions that are expected to lower the conduction safety factor to explore mechanisms of axonal and dendritic excitability. As expected, reducing the extracellular Na+concentration from 150 to ∼60 mM decreased the amplitude of APs recorded in the soma but surprisingly did not influence axonal conduction, as monitored by measuring Ca2+transients. Furthermore, reliable axonal conduction was observed in dilute (20 nM) tetrodotoxin (TTX), despite a similar reduction in AP amplitude. In contrast, the Ca2+transient measured along dendrites was markedly reduced in low Na+, although still mediated by TTX-sensitive Na+channels. Dendritic action-potential evoked Ca2+transients were also markedly reduced in 20 nM TTX. These data provide further evidence that strongly excitable axons are functionally compartmentalized from weakly excitable dendrites. We conclude that modulation of Na+currents or membrane potential by neurotransmitters or repetitive firing is more likely to influence neuronal firing before AP generation than the propagation of signals to axonal terminals. In contrast, the relatively low safety factor for back-propagating APs in dendrites would suggest a stronger effect of Na+current modulation.
Action Potential and Sodium Current in the Slowly and Rapidly Adapting Stretch Receptor Neurons of the Crayfish (Astacus astacus)
Authors: Purali Nuhan , Rydqvist Bo
Published: December 2017

Purali, Nuhan and Bo Rydqvist. Action potential and sodium current in the slowly and rapidly adapting stretch receptor neurons of the crayfish ( Astacus astacus). J. Neurophysiol. 80: 2121–2132, 1998. Action potentials (APs) and sodium current from the slowly and the rapidly adapting stretch receptor neurons in the crayfish ( Astacus astacus) were recorded with a two microelectrode voltage- and current-clamp technique. In the rapidly adapting neuron the APs had a duration of 3.2 ± 0.2 ms (means ± SE) and an amplitude of 55.2 ± 1.5 mV. In the slowly adapting receptor neuron APs had a duration of 4.1 ± 0.2 ms and an amplitude 79.9 ± 2.0 mV. APs in the rapidly adapting neuron had a larger amplitude if they were recorded from the axon. In the rapidly adapting neuron adaptation of the impulse response was prolonged by hyperpolarization or by exposure to scorpion venom. Also, sinusoidal current stimulation added to the current steps prevented impulse adaptation. Block of the potassium currents in the slowly adapting neuron resulted in a rapid adaptation of the impulse response. The maximum sodium current amplitude was 313 ± 15 nA in slowly adapting neuron and 267 ± 11 nA in the rapidly adapting neuron. The current-voltage relationship showed a hump most marked in the slowly adapting neuron and abolished when a depolarizing prepulse was given. In the rapidly adapting neuron the inactivation starts at a more negative potential ( Eh = −45 mV) and is faster compared with the slowly adapting neuron ( Eh = −41 mV). The crude scorpion venom of Leiurus quinquestriatus (ScVLq) shifted h ∞ curve toward more positive potentials and slowed down the rate of inactivation. The results indicate the possible presence of more than one Na+ channel population and that the relative density and the spatial distribution is different in the slowly and rapidly adapting neuron. The difference contributes to the adaptive properties of the two receptor neurons.
Attenuation of Delay-Period Activity of Monkey Prefrontal Neurons by an α2-Adrenergic Antagonist During an Oculomotor Delayed-Response Task
Authors: Sawaguchi T.
Published: December 2017

Sawaguchi, T. Attenuation of delay-period activity of monkey prefrontal neurons by an α2-adrenergic antagonist during an oculomotor delayed-response task. J. Neurophysiol. 80: 2200–2205, 1998. To examine the role of norepinephrine receptors in spatial working memory processes mediated by the prefrontal cortex (PFC), noradrenergic antagonists (yohimbine for α2, prazosin for α1, and propranolol for β receptors) were applied iontophoretically to neurons of the dorsolateral PFC in rhesus monkeys that performed an oculomotor delayed-response (ODR) task. The ODR task was initiated when the monkeys fixated on a central spot on a computer monitor and consisted of fixation (1 s), cue (1 of 4 peripheral cues, 0.5 s), delay (fixation cue only, 4 s), and go periods. In the go period, the subject made a memory-guided saccade to the target location that was cued before the delay period. I focused on 49 neurons that showed directional delay-period activity, i.e., a sustained increase in activity during the delay period, the magnitude of which varied significantly with the memorized target location. Iontophoretic (usually 50 nA) application of yohimbine, but not prazosin or propranolol, significantly decreased the activities of most of the neurons with directional delay-period activity ( n = 41/49, 81%). Furthermore, yohimbine attenuated the sharpness of tuning, examined by a tuning index, of delay-period activity and had a greater attenuating effect on delay-period activity than on background activity. These findings suggest that the activation of α2-adrenergic receptors in the dorsolateral PFC plays a modulatory role in neuronal processes for visuospatial working memory.
α2-Adrenoceptors Modulate NMDA-Evoked Responses of Neurons in Superficial and Deeper Dorsal Horn of the Medulla
Authors: Zhang Kai-Ming , Wang Xiao-Min , Peterson Angela M. , Chen Wen-Yan , Mokha Sukhbir S.
Published: December 2017

Kai-Ming Zhang, Xiao-Min Wang, Angela M. Peterson, Wen-Yan Chen, and Sukhbir S. Mokha. α2-Adrenoceptors modulate NMDA-evoked responses of neurons in the superficial and deeper dorsal horn of the medulla. J. Neurophysiol. 80: 2210–2214, 1998. Extracellular single unit recordings were made from neurons in the superficial and deeper dorsal horn of the medulla (trigeminal nucleus caudalis) in 21 male rats anesthetized with urethan. NMDA produced an antagonist-reversible excitation of 46 nociceptive as well as nonnociceptive neurons. Microiontophoretic application of a preferential α2-adrenoceptor (α2AR) agonist, (2-[2,6-dichloroaniline]-2-imidazoline) hydrochloride (clonidine), reduced the NMDA-evoked responses of 86% (6/7) of nociceptive-specific (NS) neurons, 82% (9/11) of wide dynamic range (WDR) neurons, and 67% (4/6) of low-threshold (LT) neurons in the superficial dorsal horn. In the deeper dorsal horn, clonidine inhibited the NMDA-evoked responses of 94% (16/17) of NS and WDR neurons and 60% (3/5) of LT neurons. Clonidine facilitated the NMDA-evoked responses in 14% (1/17) of NS, 9% (1/11) of WDR, and 33% (2/6) of LT neurons in the superficial dorsal horn. Idazoxan, an α2AR antagonist, reversed the inhibitory effect of clonidine in 90% (9/10) of neurons, whereas prazosin, an α1-adrenoceptor antagonist with affinity for α2BAR, and α2CAR, were ineffective. We suggest that activation of α2ARs produces a predominantly inhibitory modulation of the NMDA-evoked responses of nociceptive neurons in the medullary dorsal horn.
GABAA Currents in Immature Dentate Gyrus Granule Cells
Authors: Liu Ying Bing , Ye Gui-Lan , Liu Xue-Song , Pasternak Joseph F. , Trommer Barbara L.
Published: December 2017

Liu, Ying Bing, Gui-Lan Ye, Xue-Song Liu, Joseph F. Pasternak, and Barbara L. Trommer. GABAA Currents in immature dentate gyrus granule cells. J. Neurophysiol. 80: 2255–2267, 1998. We used whole cell patch clamp and gramicidin perforated patch recordings in hippocampal slices to study γ-aminobutyric acid (GABA) currents in granule cells (GCs) from juvenile rat dentate gyrus (DG). GCs are generated postnatally and asynchronously such that they can be detected at different stages of their maturation in DG within the first month. In contrast, inhibitory interneurons are generated embryonically, and their circuitry is well developed even as their target GCs and GC excitatory connections are still being formed. In this study, two GABA currents evoked in GCs by medial perforant path stimulation are compared. The first, pharmacologically isolated by glutamate receptor blockade, is the product of direct activation of GABA interneurons with monosynaptic input to the recorded GC (monosynaptic GABAA). Monosynaptic GABAA displays slight outward rectification of its current-voltage relation, is 97% eliminated by 10 μM bicuculline and coincides temporally with the excitatory components of GC postsynaptic currents as has been described for GABAA currents in other brain regions. The second is a novel GABA response that is detectable in 10 μM bicuculline and is present on GCs only at the earliest stages of their maturation. Unlike monosynaptic GABAA, this transient GABA is eliminated by glutamate receptor blockade and hence is likely to be generated by interneurons activated via an intervening glutamatergic synapse (polysynaptically). It is predominantly chloride mediated, has a relative bicarbonate/chloride permeability ratio of 26%, and is unchanged by bath-applied saclofen and strychnine or by intracellular calcium chelation. It is 97% antagonized by 100 μM picrotoxin and 99% antagonized by 100 μM bicuculline. This current is thus a relatively bicuculline (BMI)-resistant GABAA current (BMIR-GABAA). Compared with monosynaptic GABAA, BMIR-GABAA has a later peak, slower time course of decay, and marked outward rectification. Its reversal potential is 7–8 mV depolarized to that of monosynaptic GABAA whether recorded in whole cell or with gramicidin perforated patch to preserve native internal chloride concentration. Together these data may suggest that BMIR-GABAA is evoked by an anatomically segregated population of interneurons activating a unique, developmentally regulated GABAA receptor. Further, the transient nature of this current coupled with its temporal characteristics that preclude overlap with the excitatory components of the synaptic response are consistent with a role that is trophic or signaling rather than primarily inhibitory.
L-Type Ca2+ Channels Mediate the Slow Ca2+-Dependent Afterhyperpolarization Current in Rat CA3 Pyramidal Cells In Vitro
Authors: Tanabe Mitsuo , Gähwiler Beat H. , Gerber Urs
Published: December 2017

Tanabe, Mitsuo, Beat H. Gähwiler, and Urs Gerber. L-type Ca2+ channels mediate the slow Ca2+-dependent afterhyperpolarization current in rat CA3 pyramidal cells in vitro. J. Neurophysiol. 80: 2268–2273, 1998. Single-electrode voltage-clamp recordings were obtained from CA3 pyramidal cells in rat hippocampal organotypic slice cultures, and the slow Ca2+-dependent K+ current or afterhyperpolarization current ( I AHP) was elicited with brief depolarizing voltage jumps. The slow I AHP was suppressed by the selective L-type Ca2+ channel antagonists isradipine (2 μM) or nifedipine (10 μM). In contrast, neither ω-conotoxin MVIIA (1 μM) nor ω-agatoxin IVA (200 nM), N-type and P/Q-type Ca2+ channel antagonists, respectively, attenuated this slow outward current. The slow I AHP was significantly reduced by thapsigargin (10 μM), a Ca2+ ATPase inhibitor that depletes intracellular Ca2+ stores, and by ryanodine (10–100 μM), which blocks Ca2+-induced Ca2+ release from intracellular compartments. At this concentration thapsigargin did not modify high-threshold Ca2+ current, which was, however, blocked by isradipine. Thus, in hippocampal CA3 pyramidal cells, Ca2+ influx through L-type Ca2+ channels is necessary to trigger the slow I AHP. Furthermore, intracellular Ca2+-activated Ca2+ stores represent a critical component in the transduction pathway leading to the generation of the slow I AHP.
Neural Control of Rotational Kinematics Within Realistic Vestibuloocular Coordinate Systems
Authors: Smith Michael A. , Crawford J. Douglas
Published: December 2017

Smith, Michael A. and J. Douglas Crawford. Neural control of rotational kinematics within realistic vestibuloocular coordinate systems. J. Neurophysiol. 80: 2295–2315, 1998. Previous theoretical investigations of the three-dimensional (3-D) angular vestibuloocular reflex (VOR) have separately modeled realistic coordinate transformations in the direct velocity path or the nontrivial problems of converting angular velocity into a 3-D orientation command. We investigated the physiological and behavioral implications of combining both approaches. An ideal VOR was simulated using both a plant model with head-fixed eye muscle actions (standard plant) and one with muscular position dependencies that facilitate Listing's law (linear plant). In contrast to saccade generation, stabilization of the eye in space required a 3-D multiplicative (tensor) interaction between the various components of velocity and position in both models: in the indirect path of the standard plant version, but also in the direct path of the linear plant version. We then incorporated realistic nonorthogonal coordinate transformations (with the use of matrices) into both models. Each now malfunctioned, predicting ocular drift/retinal destabilization during and/or after the head movement, depending on the plant version. The problem was traced to the standard multiplication tensor, which was only defined for right-handed, orthonormal coordinates. We derived two solutions to this problem: 1) separating the brain stem coordinate transformation into two (sensory and motor) transformations that reordered and “undid” the nonorthogonalities of canals and muscle transformations, thus ensuring orthogonal brain stem coordinates, or 2) computing the correct tensor components for velocity-orientation multiplication in arbitrary coordinates. Both solutions provided an ideal VOR. A similar problem occurred with partial canal or muscle damage. Altering a single brain stem transformation was insufficient because the resulting coordinate changes rendered the multiplication tensor inappropriate. This was solved by either recomputing the multiplication tensor, or recomputing the appropriate internal sensory or motor matrix to normalize and reorthogonalize the brain stem. In either case, the multiplication tensor had to be correctly matched to its coordinate system. This illustrates that neural coordinate transformations affect not only serial/parallel projections in the brain, but also lateral projections associated with computations within networks/nuclei. Consequently, a simple progression from sensory to motor coordinates may not be optimal. We hypothesize that the VOR uses a dual coordinate transformation (i.e., both sensory and motor) to optimize intermediate brain stem coordinates, and then sets the appropriate internal tensor for these coordinates. We further hypothesize that each of these processes should optimally be capable of specific, experimentally identifiable adjustments for motor learning and recovery from damage.
Temporal Patterns and Depolarizing Actions of Spontaneous GABAA Receptor Activation in Granule Cells of the Early Postnatal Dentate Gyrus
Authors: Hollrigel Greg S. , Ross Stephen T. , Soltesz Ivan
Published: December 2017

Hollrigel, Greg S., Stephen T. Ross, and Ivan Soltesz. Temporal patterns and depolarizing actions of spontaneous GABAA receptor activation in granule cells of the early postnatal dentate gyrus. J. Neurophysiol. 80: 2340–2351, 1998. Whole cell patch-clamp recordings were used to investigate the properties of the γ-aminobutyric acid type A (GABAA) receptor-mediated spontaneous synaptic events in immature granule cells of the developing, early postnatal day (P0–P6) rat dentate gyrus. With Cs-gluconate-filled whole cell patch pipettes at 0 mV in control medium, spontaneous inhibitory postsynaptic currents (sIPSCs) occurred in prominent bursts (peak amplitude of the bursts 406.9 ± 58.4 pA; intraburst IPSC frequency 71.0 ± 12.4 Hz) at 0.05 ± 0.02 Hz in every immature granule cell younger than P7. Between the bursts of IPSCs, lower frequency (1.7 ± 0.7 Hz), interburst IPSCs could be observed. Bicuculline and picrotoxin as well as the intracellularly applied chloride-channel blockers CsF− and 4,4′-diisothiocyanatostilbene-2,2′-disulfonic acid (DIDS) abolished the intraburst as well as the interburst IPSCs, indicating that the IPSCs were mediated by GABAA receptor channels. The bursts of IPSCs, but not the interburst IPSCs, were blocked by the simultaneous application of the glutamate receptor antagonists 2-amino-5-phosphovaleric acid and 6-cyano-7-nitroquinoxaline-2,3-dione, indicating the importance of the glutamatergic excitatory drive onto the interneurons in the early postnatal dentate gyrus. The spontaneously occurring excitatory postsynaptic currents in immature granule cells, observable after the intracellular blockade of GABAA receptor channels with CsF− and DIDS, appeared exclusively as single events at low frequencies, i.e., they did not occur in prominent bursts. Gramicidin-based perforated patch-clamp recordings determined that the reversal potential for the burst of IPSCs (−46.6 ± 3.1 mV) was more depolarized than the resting membrane potential (−54.2 ± 4.2 mV) but more hyperpolarized than the action potential threshold (−41.8 ± 1.7 mV). The depolarizing action of the bursts of synaptic events most often evoked only a single action potential per burst. Simultaneous whole cell patch recordings, with KCl-filled patch pipettes at −60 mV in current clamp from pairs of immature granule cells of the developing dentate gyrus, determined that the bursts of IPSPs took place in a similar temporal pattern but with imperfect synchrony in neighboring granule cells (average lag between the onsets of the bursts between granule cell pairs 77.7 ± 8.6 ms). These results show that the spontaneous activation of GABAA receptors in immature dentate granule cells displays unique properties that are distinct from the temporal patterns and biophysical features of spontaneous GABAA receptor activation taking place in the developing Ammon's horn and in the adult dentate gyrus.
Classification of Caudal Ventrolateral Pontine Neurons With Sympathetic Nerve-Related Activity
Authors: Barman Susan M. , Gebber Gerard L.
Published: December 2017

Barman, Susan M. and Gerard L. Gebber. Classification of caudal ventrolateral pontine neurons with sympathetic nerve-related activity. J. Neurophysiol. 80: 2433–2445, 1998. This study was designed to answer three questions concerning caudal ventrolateral pontine (CVLP) neurons whose naturally occurring discharges are correlated to sympathetic nerve discharge (SND). 1) What are the proportions of CVLP neurons that have activity correlated to both the cardiac-related and 10-Hz rhythms in SND, to only the 10-Hz rhythm, and to only the cardiac-related rhythm? 2) Do CVLP neurons with activity correlated to the cardiac-related and/or 10-Hz rhythm in SND subserve a sympathoexcitatory or sympathoinhibitory function? 3) Do CVLP neurons with activity correlated to the cardiac-related and/or 10-Hz rhythm in SND project to the thoracic spinal cord? To address these issues we recorded from 476 CVLP neurons in 24 urethan-anesthetized cats. Spike-triggered averaging, arterial pulse-triggered analysis, and coherence analysis revealed that the discharges of 66 of these neurons were correlated to inferior cardiac postganglionic SND. For 39 of these neurons, we were able to determine whether their discharges were correlated to one or both rhythms. The results showed that the CVLP contained a heterogeneous population of neurons with sympathetic nerve-related activity. The discharges of 21 neurons were correlated to both the 10-Hz and cardiac-related rhythms in SND, 9 neurons had activity correlated to only the 10-Hz rhythm, and 9 neurons had activity correlated to only the cardiac-related rhythm. The firing rates of CVLP neurons with activity correlated to both rhythms or to only the 10-Hz rhythm were decreased during the inhibition of SND induced by baroreceptor reflex activation (rapid obstruction of the abdominal aorta). These neurons are presumed to exert sympathoexcitatory actions. The time-controlled collision test verified that 11 of 12 CVLP neurons with activity correlated to both rhythms were antidromically activated by stimulation of the first thoracic segment of the spinal cord. Antidromic mapping at this level showed that the site requiring the least stimulus current to elicit the longest latency response (nearest the terminal) was in the vicinity of the intermediolateral nucleus (IML). In contrast, only 1 of 13 CVLP neurons with activity correlated to only one of the rhythms in SND could be antidromically activated by spinal stimulation. These data demonstrate for the first time that there is a direct pathway from the CVLP to the IML that is comprised almost exclusively of sympathoexcitatory neurons whose discharges are correlated to both the 10-Hz and cardiac-related rhythms in SND.
Synchronization of Golgi and Granule Cell Firing in a Detailed Network Model of the Cerebellar Granule Cell Layer
Authors: Maex Reinoud , Schutter Erik De
Published: December 2017

Maex, Reinoud and Erik De Schutter. Synchronization of Golgi and granule cell firing in a detailed network model of the cerebellar granule cell layer. J. Neurophysiol. 80: 2521–2537, 1998. The granular layer of the cerebellum has a disproportionately large number of excitatory (granule cells) versus inhibitory neurons (Golgi cells). Its synaptic organization is also unique with a dense reciprocal innervation between granule and Golgi cells but without synaptic contacts among the neurons of either population. Physiological recordings of granule or Golgi cell activity are scarce, and our current thinking about the way the granular layer functions is based almost exclusively on theoretical considerations. We computed the steady-state activity of a large-scale model of the granular layer of the rat cerebellum. Within a few tens of milliseconds after the start of random mossy fiber input, the populations of Golgi and granule cells became entrained in a single synchronous oscillation, the basic frequency of which ranged from 10 to 40 Hz depending on the average rate of firing in the mossy fiber population. The long parallel fibers ensured, through α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid-mediated synapses, a coherent excitation of Golgi cells, while the regular firing of each Golgi cell synchronized all granule cells within its axonal radius through transient activation of their γ-aminobutyric acid-A (GABAA) receptor synapses. Individual granule cells often remained silent during a few successive oscillation cycles so that their average firing rates, which could be quite variable, reflected the average activities of their mossy fiber afferents. The synchronous, rhythmic firing pattern was robust over a broad range of biologically realistic parameter values and to parameter randomization. Three conditions, however, made the oscillations more transient and could desynchronize the entire network in the end: a very low mossy fiber activity, a very dominant excitation of Golgi cells through mossy fiber synapses (rather than through parallel fiber synapses), and a tonic activation of granule cell GABAA receptors (with an almost complete absence of synaptically induced inhibitory postsynaptic currents). These three conditions were associated with a reduction in the parallel fiber activity, and synchrony could be restored by increasing the mossy fiber firing rate. The model predicts that, under conditions of strong mossy fiber input to the cerebellum, Golgi cells do not only control the strength of parallel fiber activity but also the timing of the individual spikes. Provided that their parallel fiber synapses constitute an important source of excitation, Golgi cells fire rhythmically and synchronized with granule cells over large distances along the parallel fiber axis. According to the model, the granular layer of the cerebellum is desynchronized when the mossy fiber firing rate is low.
Temporal Dynamics of Convergent Modulation at a Crustacean Neuromuscular Junction
Authors: Jorge-Rivera Juan Carlos , Sen Kamal , Birmingham J. T. , Abbott L. F. , Marder Eve
Published: December 2017

Jorge-Rivera, Juan Carlos, Kamal Sen, J. T. Birmingham, L. F. Abbott, and Eve Marder. Temporal dynamics of convergent modulation at a crustacean neuromuscular junction. J. Neurophysiol. 80: 2559–2570, 1998. At least 10 different substances modulate the amplitude of nerve-evoked contractions of the gastric mill 4 (gm4) muscle of the crab, Cancer borealis. Serotonin, dopamine, octopamine, proctolin, red pigment concentrating hormone, crustacean cardioactive peptide, TNRNFLRFamide, and SDRNFLRFamide increased and d-allatostatin-3 and histamine decreased the amplitude of nerve-evoked contractions. Modulator efficacy was frequency dependent; TNRNFLRFamide, proctolin, and dallatostatin-3 were more effective when the motor neuron was stimulated at 10 Hz than at 40 Hz, whereas the reverse was true for dopamine and serotonin. The modulators that were most effective at high stimulus frequencies produced a significant decrease in muscle relaxation time; those that were most effective at low stimulus frequencies produced modest increases in relaxation time. Thus modulator actions that appear redundant when examined only at one stimulus frequency are differentiated when a range of stimulus dynamics is studied. The effects of TNRNFLRFamide, serotonin, proctolin, dopamine, and d-allatostatin-3 on the amplitude and facilitation of nerve-evoked excitatory junctional potentials (EJPs) in the gm4 and gastric mill 6 (gm6) muscles were compared. The EJPs in gm4 have a large initial amplitude and show relatively little facilitation, whereas the EJPs in gm6 have a small initial amplitude and show considerable facilitation. Modulators that enhanced contractions also enhanced EJP amplitude; d-allatostatin-3 reduced EJP amplitude. The effects of these modulators on EJP amplitude were modest and showed no significant frequency dependence. This suggests that the frequency dependence of modulator action on contraction results from effects on excitation–contraction coupling. The modulators affected facilitation at these junctions in a manner consistent with a change in release probability. They produced a change in facilitation that is inversely related to their action on EJP amplitude.
Two-Channel Polarization Analyzer in the Sustaining Fiber-Dimming Fiber Ensemble of Crayfish Visual System
Authors: Glantz Raymon M. , McIsaac Andy
Published: December 2017

Glantz, Raymon M. and Andy McIsaac. Two-channel polarization analyzer in the sustaining fiber-dimming fiber ensemble of crayfish visual system. J. Neurophysiol. 80: 2571–2583, 1998. Polarization sensitivity (PS) was examined in two classes of neurons, sustaining fibers and dimming fibers, in the medulla externa (second optic neuropile) of the crayfish, Pacifasticus leniusculus. Visual responses were recorded intracellularly and extracellularly. The influence of e-vector orientation (θ) was probed in steady-state responses, with brief flashes and with a rotating polarizer. The results indicate that the entire sustaining fiber population appears to be maximally sensitive to vertically polarized light. Although the evidence is less complete for dimming fibers, they appear to be maximally inhibited by vertically polarized light and excited by horizontally polarized light. Thus the sustaining fibers and dimming fibers form a two-channel polarization analyzer that captures the main features of the polarization system established in photoreceptors and lamina monopolar cells. The available evidence suggests that this two-channel system has the same characteristics across most or all of the retinula. Lateral inhibition in sustaining fibers is differentially sensitive to θ. Inhibition is substantial at θ = 90° (horizontal) and essentially absent at θ = 0°. The details of the sustaining fiber polarization response closely follow features established in more peripheral neurons, including the magnitude of PS, enhanced responsiveness to a changing e-vector, and modest directionality to a changing e-vector in∼40% of the cells.
Representation of Touch Location by a Population of Leech Sensory Neurons
Authors: Lewis John E. , Kristan William B.
Published: December 2017

Lewis, John E. and William B. Kristan, Jr. Representation of touch location by a population of leech sensory neurons. J. Neurophysiol. 80: 2584–2592, 1998. To form accurate representations of the world, sensory systems must accurately encode stimuli in the spike trains of populations of neurons. The nature of such neuronal population codes is beginning to be understood. We characterize the entire sensory system underlying a simple withdrawal reflex in the leech, a bend directed away from the site of a light touch. Our studies show that two different populations of mechanosensory neurons each encode touch information with an accuracy that can more than account for the behavioral output. However, we found that only one of the populations, the P cells, is important for the behavior. The sensory representation of touch location is based on the spike counts in all of the four P cells. Further, fewer than three action potentials in the P cell population, occurring during the first 100 ms of a touch stimulus, may be required to process touch location information to produce the appropriately directed bend.
NMDA Receptor Mechanisms Contribute to Neuroplasticity Induced in Caudalis Nociceptive Neurons by Tooth Pulp Stimulation
Authors: Chiang Chen Yu , Park Soo Joung , Kwan Chun L. , Hu James W. , Sessle Barry J.
Published: December 2017

Chiang, Chen Yu, Soo Joung Park, Chun L. Kwan, James W. Hu, and Barry J. Sessle. NMDA receptor mechanisms contribute to neuroplasticity induced in caudalis nociceptive neurons by tooth pulp stimulation. J. Neurophysiol. 80: 2621–2631, 1998. We recently demonstrated that application of mustard oil (MO), a small-fiber excitant and inflammatory irritant, to the rat maxillary molar tooth pulp induces significant and prolonged increases in jaw muscle electromyographic (EMG) activity that are suggestive of central neuroplasticity. Because small-fiber afferents, including pulp afferents, access nociceptive neurons in trigeminal (V) subnucleus caudalis, this study examined whether pulpal application of MO induces neuroplastic changes in caudalis nociceptive neurons (wide dynamic range and nociceptive specific) and whether central N-methyl-d-aspartate (NMDA) receptor mechanisms are involved in these MO-induced neuroplastic changes. After pretreatment with vehicle (saline, 10 μl i.t.) to the surface of the medulla, the pulpal application of MO to the maxillary molar tooth pulp produced a significant increase in neuronal spontaneous activity, a significant expansion of the pinch and/or tactile mechanoreceptive field (RF), a significant decrease in mechanical threshold, and significant increases in neuronal responses to graded pinch stimuli. Compared with vehicle-treated rats, pretreatment with the NMDA receptor antagonist MK-801 (10 μg/10 μl i.t.) followed by MO application to the pulp in another group of rats significantly reduced or abolished these MO-induced neuroplastic changes in nociceptive neurons. In another group of rats pretreated with saline (intrathecally), mineral oil application to the pulp did not show any significant changes in spontaneous activity or RF properties over the 40-min observation period. The pulpal application of MO in other rats (pretreated with saline, intrathecally) did not produce any significant neuroplastic changes in caudalis low-threshold mechanoreceptive neurons. These results indicate that the MO-induced activation of molar pulpal afferents can produce profound NMDA receptor-related neuroplastic changes in caudalis nociceptive neurons. Such neuroplastic changes may contribute to the hyperalgesia and spread of pain that can be associated with pulpal inflammation.
Mechanosensitive Pelvic Nerve Afferent Fibers Innervating the Colon of the Rat are Polymodal in Character
Authors: Su X. , Gebhart G. F.
Published: December 2017

Su, X. and G. F. Gebhart. Mechanosensitive pelvic nerve afferent fibers innervating the colon of the rat are polymodal in character. J. Neurophysiol. 80: 00–00, 1998. This report describes the chemical and thermal sensitivity of mechanosensitive pelvic nerve afferent fibers innervating the colon of the rat. A total of 51 fibers in the S1 dorsal root, identified by electrical stimulation of the pelvic nerve, were studied. An approximately 7 cm length of descending colon was isolated in situ to permit intracolonic perfusion and distension with Krebs solution. Reproducibility of responses to repetitive colorectal distension (CRD, 40 mmHg, 30 s, every 4 min) was documented. All fibers gave monotonic, incrementing responses to graded CRD (5 to 60 mmHg). Increases ( n = 6) or decreases ( n = 6) in pH of the perfusate failed to produce any change in resting activity or responses to CRD. Infusion of bile salts increased the resting activity of 6/6 fibers in a concentration-dependent manner, but did not affect the magnitude of responses to CRD. After intracolonic instillation of an inflammatory soup (bradykinin 10−5M, PGE210−5M, serotonin 10−5M, histamine 10−5M and KCl 10−3M), 13/22 fibers exhibited sensitization of responses to CRD. Seventy-three percent of 45 fibers tested responded to intracolonic perfusion of heated Krebs solution. The estimated threshold for response was 45°C and response magnitude increased with the temperature. A smaller proportion (30%) of 37 fibers tested responded to intracolonic perfusion of cold Krebs solution. The estimated threshold for response was 28°C. Of 36 fibers tested, 8 were activated by both heat and cold; typically, fibers activated by heat did not respond to cold. In a sample of 26 fibers tested for response to all three modalities of stimulation, 11 responded to mechanical, chemical and thermal stimuli; the remaining 15 responded to mechanical and either chemical or thermal stimulation. Changes in intracolonic pressure in response to chemical and thermal stimuli were also evaluated. Inflammatory soup and bile salts did not change intracolonic pressure; heat and cold produced a modest decrease and increase in muscle tension, respectively. These results document that mechanosensitive pelvic nerve afferent fibers are also chemosensitive and/or thermosensitive, supporting the notion that visceral mechanoreceptors in general are likely polymodal in character.
Functional MRI of Galvanic Vestibular Stimulation
Authors: Lobel Elie , Kleine Justus F. , Bihan Denis Le , Leroy-Willig Anne , Berthoz Alain
Published: December 2017

Lobel, Elie, Justus F. Kleine, Denis Le Bihan, Anne Leroy-Willig A, and Alain Berthoz. Functional MRI of galvanic vestibular stimulation. J. Neurophysiol. 80: 2699–2709, 1998. The cortical processing of vestibular information is not hierarchically organized as the processing of signals in the visual and auditory modalities. Anatomic and electrophysiological studies in the monkey revealed the existence of multiple interconnected areas in which vestibular signals converge with visual and/or somatosensory inputs. Although recent functional imaging studies using caloric vestibular stimulation (CVS) suggest that vestibular signals in the human cerebral cortex may be similarly distributed, some areas that apparently form essential constituents of the monkey cortical vestibular system have not yet been identified in humans. Galvanic vestibular stimulation (GVS) has been used for almost 200 years for the exploration of the vestibular system. By contrast with CVS, which mediates its effects mainly via the semicircular canals (SCC), GVS has been shown to act equally on SCC and otolith afferents. Because galvanic stimuli can be controlled precisely, GVS is suited ideally for the investigation of the vestibular cortex by means of functional imaging techniques. We studied the brain areas activated by sinusoidal GVS using functional magnetic resonance imaging (fMRI). An adapted set-up including LC filters tuned for resonance at the Larmor frequency protected the volunteers against burns through radio-frequency pickup by the stimulation electrodes. Control experiments ensured that potentially harmful effects or degradation of the functional images did not occur. Six male, right-handed volunteers participated in the study. In all of them, GVS induced clear perceptions of body movement and moderate cutaneous sensations at the electrode sites. Comparison with anatomic data on the primate cortical vestibular system and with imaging studies using somatosensory stimulation indicated that most activation foci could be related to the vestibular component of the stimulus. Activation appeared in the region of the temporo-parietal junction, the central sulcus, and the intraparietal sulcus. These areas may be analogous to areas PIVC, 3aV, and 2v, respectively, which form in the monkey brain, the “inner vestibular circle”. Activation also occurred in premotor regions of the frontal lobe. Although undetected in previous imaging-studies using CVS, involvement of these areas could be predicted from anatomic data showing projections from the anterior ventral part of area 6 to the inner vestibular circle and the vestibular nuclei. Using a simple paradigm, we showed that GVS can be implemented safely in the fMRI environment. Manipulating stimulus waveforms and thus the GVS-induced subjective vestibular sensations in future imaging studies may yield further insights into the cortical processing of vestibular signals.
Stereotyped Yawning Responses Induced by Electrical and Chemical Stimulation of Paraventricular Nucleus of the Rat
Authors: Sato-Suzuki Ikuko , Kita Ichiro , Oguri Mitsugu , Arita Hideho
Published: December 2017

Sato-Suzuki, Ikuko, Ichiro Kita, Mitsugu Oguri, and Hideho Arita. Stereotyped yawning responses induced by electrical and chemical stimulation of paraventricular nucleus of the rat. J. Neurophysiol. 80: 2765–2775, 1998. Yawning was evoked by electrical or chemical stimulation in the paraventricular nucleus (PVN) of anesthetized, spontaneously breathing rats. To evaluate physiological aspects of yawning, we monitored polygraphic measures as follows; a coordinated motor pattern of yawning was assessed by monitoring breathing [intercostal electromyogram (EMG)], mouth opening (digastric EMG), and stretching of the trunk (back EMG). We also recorded blood pressure (BP), heart rate, and the electrocorticogram (ECoG) to evaluate autonomic function and arousal responses during yawning. A stereotyped yawning response was reproducibly evoked by electrical stimulation or microinjection of l-glutamate or NOC-7, a nitric oxide (NO)-releasing compound, into the PVN. The stereotyped yawning response consisted of two sequential events, an initial response represented a depressor response and an arousal shift in the ECoG to lower voltage and faster rhythms. These initial changes were followed by a yawning behavior characterized by a single large inspiration with mouth opening and stretching of the trunk. A similar sequence of events occurred during spontaneous yawning; a fall in BP and ECoG arousal preceded a yawning behavior. An increase in the frequency of spontaneous yawns was also observed after microinjection of l-glutamate or NOC-7 into the PVN. Intravenous administration of NG-monomethyl-l-arginine, an inhibitor of nitric oxide synthase (NOS), prevented the stereotyped yawning response evoked by chemical stimulation of the PVN. Histological examination revealed that effective sites for the yawning responses were located in the medial part of the rostral PVN, the site of parvocellular and magnocellular neurons. NADPH-diaphorase histochemistry showed the existence of NOS-containing cells in yawning-evoked sites of the PVN. In summary, the sequential events of yawning may be generated by NOS-containing parvocellular neurons in the medial part of the rostral PVN projecting to the lower brain stem.
Activation of a Lobster Motor Rhythm-Generating Network by Disinhibition of Permissive Modulatory Inputs
Authors: Faumont Serge , Simmers John , Meyrand Pierre
Published: December 2017

Faumont, Serge, John Simmers, and Pierre Meyrand. Activation of a lobster motor rhythm-generating network by disinhibition of permissive modulatory inputs. J. Neurophysiol. 80: 2776–2780, 1998. Rhythm generation by the gastric motor network in the stomatogastric ganglion (STG) of the lobster Homarus gammarus is controlled by modulatory projection neurons from rostral commissural ganglia (CoGs); blocking action potential conduction in these inputs to the STG of a stomatogastric nervous system in vitro rapidly renders the gastric network silent. However, exposure of the CoGs to low Ca2+saline to block chemical synapses activates a spontaneously silent gastric network or enhances an ongoing gastric rhythm. A similar permissive effect was observed when picrotoxin was also superfused on these ganglia. We conclude that in the CoGs continuous synaptic inhibition is exerted on modulatory projection neuron(s) and that release from this inhibition allows strong activation of the gastric network.
Adaptation Properties of Two Types of Sensory Neurons in a Spider Mechanoreceptor Organ
Authors: Juusola Mikko , French Andrew S.
Published: December 2017

Juusola, Mikko and Andrew S. French. Adaptation properties of two types of sensory neurons in a spider mechanoreceptor organ. J. Neurophysiol. 80: 2781–2784, 1998. The VS-3 slit-sense organs of the tropical wandering spider Cupiennius salei contain two types of mechanosensory neurons with similar morphology but different adaptation properties. We measured the changes in membrane potential produced by mechanical stimulation and by electric current stimulation in a large number of neurons of both types. No significant differences were found between the passive membrane properties of the two groups, but there were significant differences in the extent and time course of receptor potential adaptation between the two types of neurons. These data, combined with the responses to suprathreshold electrical stimuli, indicate that adaptational differences exist at several stages in these neurons but that active membrane conductances dominate the overall behavior. The passive membrane measurements also indicate that effective voltage clamp of the receptor current at the tips of the sensory dendrites is possible in these neurons.
Temporal and Spatial Response to Second-Order Stimuli in Cat Area 18
Authors: Mareschal Isabelle , Baker Curtis L.
Published: December 2017

Mareschal, Isabelle and Curtis L. Baker, Jr. Temporal and spatial response to second-order stimuli in cat area 18. J. Neurophysiol. 80: 2811–2823, 1998. Approximately one-half of the neurons in cat area 18 respond to contrast envelope stimuli, consisting of a sinewave carrier whose contrast is modulated by a drifting sinewave envelope of lower spatial frequency. These stimuli should fail to elicit a response from a conventional linear neuron because they are designed to contain no spatial frequency components within the cell's luminance-defined frequency passband. We measured neurons' responses to envelope stimuli by varying both the drift rate and spatial frequency of the contrast modulation. These data were then compared with the same neurons' spatial and temporal properties obtained with luminance-defined sinewave gratings. Most neurons' responses to the envelope stimuli were spatially and temporally bandpass, with bandwidths comparable with those measured with luminance gratings. The temporal responses of these neurons (temporal frequency tuning and latency) were systematically slower when tested with envelope stimuli than with luminance gratings. The simplest kind of model that can accommodate these results is one having separate, parallel streams of bandpass processing for luminance and envelope stimuli.