bluuebunny/crossref_metadata_2025 huggingface dataset:
Time Course and Magnitude of Movement-Related Gating of Tactile Detection in Humans. I. Importance of Stimulus Location
Authors: Williams Stephan R. , Shenasa Jafar , Chapman C. Elaine
Published: December 2017

Williams, Stephan R., Jafar Shenasa, and C. Elaine Chapman. Time course and magnitude of movement-related gating of tactile detection in humans. I. Importance of stimulus location. J. Neurophysiol. 79: 947–963, 1998. The time course and spatial extent of movement-related suppression of the detection of weak electrical stimuli (intensity, 90% detected at rest) was determined in 118 experiments carried out in 47 human subjects. Subjects were trained to perform a rapid abduction of the right index finger (D2) in response to a visual cue. Stimulus timing was calculated relative to the onset of movement and the onset of electromyographic (EMG) activity. Electrical stimulation was delivered to 10 different sites on the body, including sites on the limb performing the movement (D2, D5, hand, forearm and arm) as well as several distant sites (contralateral arm, ipsilateral leg). Detection of stimuli applied to the moving digit diminished significantly and in a time-dependent manner, with the first significant decrease occurring 120 ms before movement onset and 70 ms before the onset of EMG activity. Movement-related and time-dependent effects were obtained at all stimulation sites on the homolateral arm as well as the adjacent trunk. A pronounced spatiotemporal gradient was observed: the magnitude of the movement-related decrease in detectability was greatest and earliest at sites closest to the moving finger and progressively weaker and later at more proximal sites. When stimuli were applied to the distant sites, only a small (∼10%), non-time–dependent decrease was observed during movement trials. A simple model of perceptual performance adequately described the results, providing insight into the distribution of movement-related inhibitory controls within the CNS.
Dorsal Horn Spatial Representation of Simple Cutaneous Stimuli
Authors: Brown Paul B. , Millecchia Ronald , Lawson Jeffrey J. , Stephens Stephanie , Harton Paul , Culberson James C.
Published: December 2017

Brown, Paul B., Ronald Millecchia, Jeffrey J. Lawson, Stephanie Stephens, Paul Harton, and James C. Culberson. Dorsal horn spatial representation of simple cutaneous stimuli. J. Neurophysiol. 79: 983–998, 1998. A model of lamina III–IV dorsal horn cell receptive fields (RFs) has been developed to visualize the spatial patterns of cells activated by light touch stimuli. Low-threshold mechanoreceptive fields (RFs) of 551 dorsal horn neurons recorded in anesthetized cats were characterized by location of RF center in cylindrical coordinates, area, length/width ratio, and orientation of long axis. Best-fitting ellipses overlapped actual RFs by 90%. Exponentially smoothed mean and variance surfaces were estimated for these five variables, on a grid of 40 points mediolaterally by 20/segment rostrocaudally in dorsal horn segments L4–S1. The variations of model RF location, area, and length/width ratio with map location were all similar to previous observations. When elliptical RFs were simulated at the locations of the original cells, the RFs of real and simulated cells overlapped by 64%. The densities of cell representations of skin points on the hindlimb were represented as pseudocolor contour plots on dorsal view maps, and segmental representations were plotted on the standard views of the leg. Overlap of modeled and real segmental representations was at the 84% level. Simulated and observed RFs had similar relations between area and length/width ratio and location on the hindlimb: r( A) = 0.52; r( L/ W) = 0.56. Although the representation of simple stimuli was orderly, and there was clearly only one somatotopic map of the skin, the representation of a single point often was not a single cluster of active neurons. When two-point stimuli were simulated, there usually was no fractionation of response zones or addition of new zones. Variation of stimulus size (area of skin contacted) produced less variation of representation size (number of cells responding) than movement of stimuli from one location to another. We conclude that stimulus features are preserved poorly in their dorsal horn spatial representation and that discrimination mechanisms that depend on detection of such features in the spatial representation would be unreliable.
Spatial View Cells in the Primate Hippocampus: Effects of Removal of View Details
Authors: Robertson Robert G. , Rolls Edmund T. , Georges-François Pierre
Published: December 2017

Robertson, Robert G., Edmund T. Rolls, and Pierre Georges-François. Spatial view cells in the primate hippocampus: effects of removal of view details. J. Neurophysiol. 79: 1145–1156, 1998. Hippocampal function was analyzed by making recordings from hippocampal formation neurons in macaques actively walking in the laboratory. “Spatial view” cells, which respond when the monkey looks at a part of the environment were analyzed. It is shown that many of these cells retain their spatial characteristics when the view details are obscured totally by curtains and by darkness. It is shown that many of these cells respond more when the monkey is gazing toward one location in the room than toward other locations, even though none of the view details can be seen. Such cells were found in the CA1 region, the parahippocampal gyrus, and the presubiculum. Other cells stopped responding when the monkey looked toward the normally effective location in the environment if the view details were obscured. These cells were in the CA3 region of the hippocampus. The results indicate that for CA3 cells, the visual input is necessary for the normal spatial response of the neurons, and for other cells in the primate hippocampal formation, the response still depends on the monkey gazing toward that location in space when the view details are obscured. These latter cells therefore could reflect the operation of a memory system, in which the neuronal activity can be triggered by factors that probably include not only eye position command/feedback signals, but also probably vestibular and/or proprioceptive inputs. This representation of space “out there” would be an appropriate part of a primate memory system involved in memories of where in an environment an object was seen and more generally in the memory of particular events or episodes for which a spatial component normally provides part of the context.
Drugs Affecting Phospholipase C-Mediated Signal Transduction Block the Olfactory Cyclic Nucleotide-Gated Current of Adult Zebrafish
Authors: Ma Li , Michel William C.
Published: December 2017

Ma, Li and William C. Michel. Drugs affecting phospholipaseC-mediated signal transduction block the olfactory cyclic nucleotide-gated current of adult zebrafish. J. Neurophysiol. 79: 1183–1192, 1998. Amino acid and bile salt odorants are detected by zebrafish with relatively independent odorant receptors, but the transduction cascade(s) subsequently activated by these odorants remains unknown. Electro-olfactogram recording methods were used to determine the effects of two drugs, reported to affect phospholipase C (PLC)/inositol tripohsphate (IP3)-mediated olfactory transduction in other vertebrate species, on amino acid and bile salt-evoked responses. At the appropriate concentrations, either an IP3-gated channel blocker, ruthenium red (0.01–0.1 μM), or a PLC inhibitor, neomycin (50 μM), reduced amino-acid–evoked responses to a significantly greater extent than bile salt-evoked responses. Excised patch recording techniques were used to measure the affects of these drugs on second-messenger–activated currents. Ruthenium red and neomycin are both effective blockers of the olfactory cyclic nucleotide-gated (CNG) current. Both drugs blocked the CNG channel in a voltage-dependent and reversible manner. No IP3-activated currents could be recorded. The differential effects of ruthenium red and neomycin on odor-evoked responses suggest the activation of multiple transduction cascades. The nonspecific actions of these drugs on odor-activated transduction pathways and our inability to record an IP3-activated current do not permit the conclusion that zebrafish, like other fish species, use a PLC/IP3-mediated transduction cascade in the detection of odorants.
Whole Cell Patch-Clamp Recordings of Rat Midbrain Dopaminergic Neurons Isolate a Sulphonylurea- and ATP-Sensitive Component of Potassium Currents Activated by Hypoxia
Authors: Guatteo E. , Federici M. , Siniscalchi A. , Knöpfel T. , Mercuri N. B. , Bernardi G.
Published: December 2017

Guatteo, E., M. Federici, A. Siniscalchi, T. Knöpfel, N. B. Mercuri, and G. Bernardi. Whole cell patch-clamp recordings of rat midbrain dopaminergic neurons isolate a sulphonylurea- and ATP-sensitive component of potassium currents activated by hypoxia. J. Neurophysiol. 79: 1239–1245, 1998. The effects of brief (2–4 min) hypoxia on presumed dopaminergic “principal” neurons of the rat ventral mesencephalon were investigated by using either intracellular or whole cell patch-clamp recordings in in vitro conditions. Under single-electrode voltage clamp, with sharp microelectrode ( V h −60 mV), a brief hypoxia caused an outward current (hypoOUT) of 110.2 ± 15.2 (SE) pA ( n = 18), which was followed by a posthypoxic outward current (posthypoOUT) of 149.6 ± 10.6 pA ( n = 18). Although the hypoOUT reversed at −83.7 ± 3.8 mV ( n = 18), the posthypoOUT did not reverse. The K+ ATP-blocking sulphonylureas tolbutamide (100 μM) and glibenclamide (30 μM), significantly reduced the peak of the hypoOUT by 47.6 ± 7.7% ( n = 16) and 54.18 ± 7.5% ( n = 3), respectively. In contrast, they did not affect the posthypoOUT. Extracellular barium (300 μM to 1 mM) almost abolished the hypoOUT, leaving the posthypoOUT unchanged. The large K+ channel blocker charybdotoxin (10–50 nM), depressed the hypoOUT after tolbutamide treatment. To investigate whether or not cytosolic factors might control the development of the hypoOUT, we dialyzed the principal neurons by patch-clamp recordings ( V h −60 mV). Under whole cell recordings hypoxia evoked an hypoOUT of 70.2 ± 14.5 pA that reversed polarity at −87.9 ± 5.1 mV ( n = 8). A small posthypoxic response was detected upon reoxygenation in a few neurons (4 out of 14). Three different sulphonylureas, tolbutamide (100 μM), glibenclamide (10–30 μM), and glipizide (100 nM) completely blocked the hypoOUT in patch-clamped neurons. The hypoOUT was also abolished by extracellular BaCl2 (300 μM). When the content of ATP in the dialyzate was raised from 2 to 10 mM no outward current/hyperpolarization was evoked by hypoxia. These data suggest that the hypoOUT, in principal neurons, is a complex response sustained by at least two barium-sensitive components: 1) an ATP-dependent, sulphonylurea-sensitive K+ conductance which could be isolated by the patch-clamp techniques and 2) a K+ conductance remaining after tolbutamide in intracellularly recorded neurons, which is sensitive to charybdotoxin and dependent on dialyzable cytosolic factors.
Effect of Cerebellar Inactivation by Lidocaine Microdialysis on the Vestibuloocular Reflex in Goldfish
Authors: McElligott James G. , Beeton Phyllis , Polk Jeffrey
Published: December 2017

McElligott, J. G., Phyllis Beeton, and Jeffrey Polk. Effect of cerebellar inactivation by lidocaine microdialysis on the vestibuloocular reflex in goldfish. J. Neurophysiol. 79: 1286–1294, 1998. Vestibuloocular reflex performance and adaptation were examined during vestibulocerebellar inactivation by localized lidocaine microdialysis or injection in goldfish. In the light, eye velocity perfectly compensated for head velocity (Vis-VOR) during sinusoidal yaw rotation (1/8 Hz ± 20°). In the dark, the reflex (VOR) gain was slightly reduced (gain ≈ 0.8–0.9). In neither Vis-VOR nor VOR, was gain altered after 1 h of lidocaine microdialysis in the vestibulocerebellum. Before adaptation of reflex gain, the initial suppression or augmentation of Vis-VOR reflex gain produced by in-phase or out-of-phase visual-vestibular stimulation was also unaffected by cerebellar inactivation. Subsequently, 3 h of adaptive reflex training in either the in-phase or out-of-phase paradigm (acquisition phase) respectively decreased (0.30 ± 0.09) or increased (1.60 ± 0.08) VOR gain during artificial cerebral spinal fluid (CSF) microdialysis. However, microdialysis of lidocaine completely blocked adaptive gain changes during a 3–4 h period of continuous application. This effect was reversible because VOR gain changes were produced 1 h after lidocaine was replaced with CSF as the dialysate. After adaptive training, bilateral CSF injections (0.25 μl/side) into the vestibulocerebellum did not alter the normal retention or decay of adapted gain changes during a 3 h period in the dark (retention phase). However, injection of lidocaine into the vestibulocerebellum completely blocked retention of the adapted VOR gain returning the gain to values recorded before adaptation. In contrast to either acute or chronic surgical removal, lidocaine inactivation of the cerebellum by microdialysis did not alter either Vis-VOR and VOR behavior or interactive Vis-VOR performance over a wide range of gain extending from 0.3 to 1.4. Thus short-term VOR motor learning is a dynamic process requiring either continuous operation of brain stem cerebellar loops or, alternatively, modifiable sites within or directly influenced by the cerebellum. Our data supports the latter hypothesis, because the direct brain stem VOR pathways appear to be unaltered after cerebellar inactivation, and, hence, independent of the VOR-adapted state.
Gradual Molding of the Hand to Object Contours
Authors: Santello Marco , Soechting John F.
Published: December 2017

Santello, Marco and John F. Soechting. Gradual molding of the hand to object contours. J. Neurophysiol. 79: 1307–1320, 1998. Subjects were asked to reach to and to grasp 15 similarly sized objects with the four fingers opposed to the thumb. The objects' contours differed: some presented a concave surface to the fingers, others a flat one, and yet others a convex surface. Flexion/extension at the metacarpal-phalangeal and proximal interphalangeal joints of the fingers was recorded during the reaching movement. We used discriminant analysis, cluster analysis, and information theory to determine the extent to which the shape of the hand was affected by the objects' shapes along a convexity/concavity gradient. Maximum aperture of the hand was reached about midway in the reaching movement. At that time, the hand's posture was influenced by the shape of the object to be grasped but imperfectly. The information transmitted by hand posture about object shape increased gradually and monotonically as the hand approached the object, reaching a maximum at the time the object was in the grasp of the hand. We also asked subjects to shape the hand so as to grasp the object without moving the arm. Their performance was poorer on this task in the sense that hand shape discriminated among fewer objects and that trial-to-trial variability was greater than when the distal and proximal components of the motion were linked. The results indicate that the hand is molded only gradually to the contours of an object to be grasped. Because other parameters of the motion, such as movement direction, for example, already are specified fully early on in a movement, the results also suggest that the specification of diverse aspects of a movement does not evolve at a uniform rate.
Sodium-Gated Cation Channel Implicated in the Activation of Lobster Olfactory Receptor Neurons
Authors: Zhainazarov Aslbek B. , Doolin Richard E. , Ache Barry W.
Published: December 2017

Zhainazarov, Aslbek B., Richard E. Doolin, and Barry W. Ache. Sodium-gated cation channel implicated in the activation of lobster olfactory receptor neurons. J. Neurophysiol. 79: 1349–1359, 1998. The role of Na+-activated channels in cellular function, if any, is still elusive. We have attempted to implicate a Na+-activated nonselective cation channel in the activation of lobster olfactory receptor neurons. We show that a Na+-activated channel occurs in the odor-detecting outer dendrites. With the use of pharmacological blockers of the channel together with ion substitution, we show that a substantial part of the odor-evoked depolarization in these cells can be ascribed to a Na+-activated conductance. We hypothesize, therefore, that the Na+-activated channel amplifies the receptor current as a result of being secondarily activated by the primary odor transduction pathway.
Long-Term Expression of Two Interacting Motor Pattern-Generating Networks in the Stomatogastric System of Freely Behaving Lobster
Authors: Clemens Stefan , Combes Denis , Meyrand Pierre , Simmers John
Published: December 2017

Clemens, Stefan, Denis Combes, Pierre Meyrand, and John Simmers. Long-term expression of two interacting motor pattern-generating networks in the stomatogastric system of freely behaving lobster. J. Neurophysiol. 79: 1396–1408, 1998. Rhythmic movements of the gastric mill and pyloric regions of the crustacean foregut are controlled by two stomatogastric neuronal networks that have been intensively studied in vitro. By using electromyographic recordings from the European lobster, Homarus gammarus, we have monitored simultaneously the motor activity of pyloric and gastric mill muscles for ≤3 mo in intact and freely behaving animals. Both pyloric and gastric mill networks are almost continuously active in vivo regardless of the presence of food. In unfed resting animals kept under “natural-like” conditions, the pyloric network expresses the typical triphasic pattern seen in vitro but at considerably slower cycle periods (2.5–3.5 s instead of 1–1.5 s). Gastric mill activity occurs at mean cycle periods of 20–50 s compared with 5–10 s in vitro but may suddenly stop for up to tens of minutes, then restart without any apparent behavioral reason. When conjointly active, the two networks express a strict coupling that involves certain but not all motor neurons of the pyloric network. The posterior pyloric constrictor muscles, innervated by a total of 8 pyloric (PY) motor neurons, are influenced by the onset of each gastric mill medial gastric/lateral gastric(MG/LG) neuron powerstroke burst, and for one cycle, PY neuron bursts may attain >300% of their mean duration. However, the duration of activity in the lateral pyloric constrictor muscle, innervated by the unique lateral pyloric (LP) motor neuron, remains unaffected by this perturbation. During this period after gastric perturbation, LP neuron and PY neurons thus express opposite burst-to-period relationships in that LP neuron burst duration is independent of the ongoing cycle period, whereas PY neuron burst duration changes with period length. In vitro the same type of gastro-pyloric interaction is observed, indicating that it is not dependent on sensory inputs. Moreover, this interaction is intrinsic to the stomatogastric ganglion itself because the relationship between the two networks persists after suppression of descending inputs to the ganglion. Intracellular recordings reveal that thisgastro-pyloric interaction originates from the gastric MG and LG neurons of the gastric network, which inhibit the pyloric pacemaker ensemble. As a consequence, the pyloric PY neurons, which are inhibited by the pyloric dilator (PD) neurons of the pyloric pacemaker group, extend their activity during the time that PD neuron is held silent. Moreover, there is evidence for a pyloro-gastric interaction, apparently rectifying, from the pyloric pacemakers back to the gastric MG/LG neuron group.
Specialized Electrophysiological Properties of Anatomically Identified Neurons in the Hilar Region of the Rat Fascia Dentata
Authors: Lübke Joachim , Frotscher Michael , Spruston Nelson
Published: December 2017

Lübke, Joachim, Michael Frotscher, and Nelson Spruston. Specialized electrophysiological properties of anatomically identified neurons in the hilar region of the rat fascia dentata. J. Neurophysiol. 79: 1518–1534, 1998. Because of their strategic position between the granule cell and pyramidal cell layers, neurons of the hilar region of the hippocampal formation are likely to play an important role in the information processing between the entorhinal cortex and the hippocampus proper. Here we present an electrophysiological characterization of anatomically identified neurons in the fascia dentata as studied using patch-pipette recordings and subsequent biocytin-staining of neurons in slices. The resting potential, input resistance ( RN), membrane time constant (τm), “sag” in hyperpolarizing responses, maximum firing rate during a 1-s current pulse, spike width, and fast and slow afterhyperpolarizations (AHPs) were determined for several different types of hilar neurons. Basket cells had a dense axonal plexus almost exclusively within the granule cell layer and were distinguishable by their low RN, short τm, lack of sag, and rapid firing rates. Dentate granule cells also lacked sag and were identifiable by their higher RN, longer τm, and lower firing rates than basket cells. Mossy cells had extensive axon collaterals within the hilus and a few long-range collaterals to the inner molecular layer and CA3c and were characterized physiologically by small fast and slow AHPs. Spiny and aspiny hilar interneurons projected primarily either to the inner or outer segment of the molecular layer and had a dense intrahilar axonal plexus, terminating onto somata within the hilus and CA3c. Physiologically, spiny hilar interneurons generally had higher RNvalues than mossy cells and a smaller slow AHP than aspiny interneurons. The specialized physiological properties of different classes of hilar neurons are likely to be important determinants of their functional operation within the hippocampal circuitry.
Position and Velocity Coupling of Postural Sway to Somatosensory Drive
Authors: Jeka John , Oie Kelvin , Schöner Gregor , Dijkstra Tjeerd , Henson Elaine
Published: December 2017

Jeka, John, Kelvin Oie, Gregor Schöner, Tjeerd Dijkstra, and Elaine Henson. Position and velocity coupling of postural sway to somatosensory drive. J. Neurophysiol. 79: 1661–1674, 1998. Light touch contact of a fingertip to a stationary surface provides orientation information that enhances control of upright stance. Slight changes in contact force at the fingertip lead to sensory cues about the direction of body sway, allowing attenuation of sway. In the present study, the coupling of postural sway to a moving contact surface was investigated in detail. Head, center of mass, and center of pressure displacement were measured as the contact surface moved rhythmically at 0.1, 0.2, 0.4, 0.6, and 0.8 Hz. Stimulus amplitude decreased with frequency to maintain peak velocity constant across frequency. Head and body sway were highly coherent with contact surface motion at all frequencies except 0.8 Hz, where a drop-off in coherence was observed. Mean frequency of head and body sway matched the driving frequency ≤0.4 Hz. At higher frequencies, non-1:1 coupling was evident. The phase of body sway relative to the touch plate averaged 20–30° at 0.1-Hz drive and decreased approximately linearly to −130° at 0.8-Hz drive. System gain was ∼1 across frequency. The large phase lags observed cannot be accounted for with velocity coupling alone but indicate that body sway also was coupled to the position of the touch plate. Fitting of a linear second-order model to the data suggests that postural control parameters are not fixed but adapt to the moving frame of reference. Moreover, coupling to both position and velocity suggest that a spatial reference frame is defined by the somatosensory system.
Distribution and Characteristics of Poststimulus Effects in Proximal and Distal Forelimb Muscles From Red Nucleus in the Monkey
Authors: Belhaj-Saïf Abderraouf , Karrer Jennifer Hill , Cheney Paul D.
Published: December 2017

Belhaj-Saı̈f, Abderraouf, Jennifer Hill Karrer, and Paul D. Cheney. Distribution and characteristics of poststimulus effects in proximal and distal forelimb muscles from red nucleus in the monkey. J. Neurophysiol. 79: 1777–1789, 1998. We used stimulus-triggered averaging (StTA) of electromyographic (EMG) activity to investigate two major questions concerning the functional organization of the magnocellular red nucleus (RNm) for reaching movements in the macaque monkey. The first is whether the clear preference toward facilitation of extensor muscles we have reported in previous studies for distal (wrist and digit) forelimb muscles also exists for proximal muscles (shoulder and elbow). The second question is whether distal and proximal muscles may be cofacilitated from RNm suggesting the representation of functional muscle synergies for coordinated reaching movements. Two monkeys were trained to perform a prehension task requiring multijoint coordination of the forelimb. EMG activity was recorded from 24 forelimb muscles including 5 shoulder, 7 elbow, 5 wrist, 5 digit, and 2 intrinsic hand muscles. Microstimulation (20 μA at 20 Hz) was delivered throughout the movement task. From 137 microstimulation sites in the RNm, a total of 977 poststimulus effects was obtained including 733 poststimulus facilitation effects (PStF) and 244 poststimulus suppression effects (PStS). Of the PStF effects, 58% were obtained from distal muscles; 42% from proximal muscles. Digit muscles were more frequently facilitated (35%) than the wrist, elbow, or shoulder muscles (20, 24, and 18%, respectively). The intrinsic hand muscles were infrequently facilitated (3%). At all joints tested, PStF was more common in extensor muscles than flexor muscles. This extensor preference was very strong for shoulder (85%), wrist (85%), and digit muscles (94%) and weaker for elbow muscles (60%). Of the PStS effects, 65% were in distal muscles and 35% in proximal muscles. Interestingly, the flexor muscles were more frequently inhibited from RNm than extensor muscles. At 72% of stimulation sites, at least two muscles were facilitated. The majority of these sites (61%) cofacilitated both proximal and distal muscles. At the remaining sites (39%), PStF was observed in either the proximal (17%) or distal muscles (22%). Facilitation most often involved combinations of shoulder, elbow, and distal muscles (30%) or shoulder and distal muscles (26%). Only rarely were intrinsic hand muscles part of the total muscle synergy. Our results show that the RNm 1) controls both proximal and distal muscles but the strength of influence is biased toward distal muscles, 2) preferentially controls extensor muscles not only at distal forelimb joints but also at proximal joints, and 3) output zones cofacilitate synergies of proximal and distal muscles involved in the control of forelimb reaching movements.
Prenatal Dietary Choline Supplementation Decreases the Threshold for Induction of Long-Term Potentiation in Young Adult Rats
Authors: Pyapali Gowri K. , Turner Dennis A. , Williams Christina L. , Meck Warren H. , Swartzwelder H. Scott
Published: December 2017

Pyapali, Gowri K., Dennis A. Turner, Christina L. Williams, Warren H. Meck, and H. Scott Swartzwelder. Prenatal dietary choline supplementation decreases the threshold for induction of long-term potentiation in young adult rats. J. Neurophysiol. 79: 1790–1796, 1998. Choline supplementation during gestation in rats leads to augmentation of spatial memory in adulthood. We hypothesized that prenatal (E12–E17) choline supplementation in the rat would lead to an enhancement of hippocampal synaptic plasticity as assessed by long-term potentiation (LTP) at 3–4 mo of age. LTP was assessed blindly in area CA1 of hippocampal slices with first suprathreshold (above threshold for LTP generation in control slices) theta-burst stimulus trains. The magnitude of potentiation after these stimuli was not different between slices from control and prenatally choline supplemented animals. Next, threshold (reliably leading to LTP generation in control slices) or subthreshold theta-burst stimulus trains were applied to slices from control, prenatally choline-supplemented, and prenatally choline-deprived rats. Threshold level stimulus trains induced LTP in slices from both the control and choline-supplemented rats but not in those from the choline-deficient rats. Subthreshold stimulus trains led to LTP induction in slices from prenatally choline-supplemented rats only. These observations indicate that prenatal dietary manipulation of the amino acid, choline, leads to subsequent significant alterations of LTP induction threshold in adult animals.
Kinetic Analysis of Glycine Receptor Currents in Ventral Cochlear Nucleus
Authors: Harty T. Patrick , Manis Paul B.
Published: December 2017

Harty, T. Patrick and Paul B. Manis. Kinetic analysis of glycine receptor currents in ventral cochlear nucleus. J. Neurophysiol. 79: 1891–1901, 1998. Glycine plays an important role as an inhibitory neurotransmitter in the ventral cochlear nucleus. However, little is known about the kinetic behavior of glycine receptors. The present study examines the kinetics of the native inhibitory glycine receptors in neurons of the ventral cochlear nucleus, using outside-out patches from acutely dissociated cells and a fast flow system. Steps into 1 mM glycine revealed fast phases of desensitization with time constants of 13 and 129 ms, that together produced a 40% reduction in current from the peak response. Slower desensitization phases also were observed. After removal of glycine, currents deactivated with two time constants of 15 and 68 ms, and these rates were independent of the glycine concentration between 0.2 and 1 mM. Recovery from desensitization was slow relative to desensitization itself. These results demonstrate that glycine receptors can exhibit faster rates of desensitization and deactivation than previously reported.
Depression of Synaptic Efficacy at Intermolt in Crayfish Neuromuscular Junctions by 20-Hydroxyecdysone, a Molting Hormone
Authors: Cooper Robin L. , Ruffner Marvin E.
Published: December 2017

Cooper, Robin L. and Marvin E. Ruffner. Depression of synaptic efficacy at intermolt in crayfish neuromuscular junctions by 20-hydroxyecdysone, a molting hormone. J. Neurophysiol. 79: 1931–1941, 1998. This report demonstrates that ecdysteroids can reduce synaptic transmission at an intermolt stage of a crustacean tonic neuromuscular junction by acting at a presynaptic site. The steroid molting hormone, 20-hydroxyecdysone (20-HE), appears to act through a rapid, nongenomic mechanism that decreases the probability of synaptic vesicle release and reduces the number of release sites. Quantal analysis revealed that fewer vesicles were released for a given stimulus when 20-HE was present, and this in turn accounted for the reduced synaptic efficacy. Reduced synaptic efficacy produced smaller evoked postsynaptic currents and smaller excitatory postsynaptic potentials (EPSPs) across the muscle fiber membrane. The reduction in EPSPs was observed among muscle fibers that were innervated by high- or low-output terminals. The behavior of crustaceans/crayfish during the molt cycle, when 20-HE is high, may be explained by the reduction in synaptic transmission. Crustaceans become quiescent during the premolt periods as do insects. The effects of 20-HE can be reversed with the application of the crustacean neuromodulator serotonin, which enhances synaptic transmission.
Muscarinic Agonist–Induced Burst Firing in Immature Rat Olfactory Cortex Neurons In Vitro
Authors: Postlethwaite M. , Constanti A. , Libri V.
Published: December 2017

Postlethwaite, M., A. Constanti, and V. Libri. Muscarinic agonist–induced burst firing in immature rat olfactory cortex neurons in vitro. J. Neurophysiol. 79: 2003–2012, 1998. Age-related changes in pre-/postsynaptic muscarinic (mAChR) and metabotropic-glutamate (mGluR) responsiveness were studied in slices of olfactory cortex from both immature [postnatal day 16–22 ( P16–P22)] and adult (≥P40) rats, using a conventional intracellular recording technique. In adult neurons, bath application of the mAChR agonist oxotremorine-M (OXO-M; 10 μM), or the selective mGluR agonist 1-aminocyclopentane-1S-3R-dicarboxylic acid (1S,3R-ACPD; 10 μM) evoked sustained membrane depolarizations, increases in input resistance, intense repetitive firing, and the appearance of a slow poststimulus afterdepolarizing potential (sADP). Excitatory postsynaptic potentials (EPSPs) evoked by local electrical stimulation of association fiber terminals were also depressed. In contrast, in neurons from immature slices, the 10 μM OXO-M–induced membrane depolarization was followed by the appearance of spontaneous rhythmic epileptiform activity, which was voltage independent and reversible on drug wash out. Epileptiform bursts were abolished or reduced by coapplication of tetrodotoxin (1 μM), atropine (1 μM), pirenzepine (100–200 nM), the N-methyl-d-aspartate (NMDA) receptor antagonist dl-amino-5-phosphonovaleric acid (dl-APV; 100 μM), the non-NMDA receptor antagonist 6-cyano-7-nitroquinoxaline-2,3-dione (CNQX; 5–20 μM), the anesthetic-sedative barbiturate pentobarbitone (100 μM), or by raising the extracellular Mg2+concentration, whereas a clear facilitatory effect was exhibited by the selective γ-aminobutyric acid-A (GABAA) receptor blocker (−)-bicuculline methiodide (10 μM). The epileptogenic effects induced by OXO-M were indistinguishable from those produced by 4-aminopyridine (4-AP; 100–200 μM), although these latter actions were unaffected by atropine. In slices from immature animals, electrical stimulation of layer III association fibers in the presence of 10 μM OXO-M was accompanied by a dramatic prolongation of evoked depolarizing postsynaptic potentials (PSPs), with the appearance of recurrent superimposed spike discharges. This effect was readily reversed on wash out of OXO-M. No comparable age-dependent differences were observed in the nature or time course of 1S,3R-ACPD–evoked pre- (or post)synaptic responses, even in immature cells where muscarinic epileptiform activity had previously been demonstrated. We suggest that the overall susceptibility toward muscarinic-induced epileptiform discharge in immature olfactory cortical neurons may depend on the functional integrity of presynaptic inhibitory mAChRs; additional contributing mechanisms were also considered.
Off-Centric Rotation Axes in Natural Head Movements: Implications for Vestibular Reafference and Kinematic Redundancy
Authors: Medendorp W. P. , Melis B.J.M. , Gielen C.C.A.M. , Gisbergen J.A.M. Van
Published: December 2017

Medendorp, W. P., B.J.M. Melis, C.C.A.M. Gielen, and J.A.M. Van Gisbergen. Off-centric rotation axes in natural head movements: implications for vestibular reafference and kinematic redundancy. J. Neurophysiol. 79: 2025–2039, 1998. Until now, most studies concerning active head movements in three dimensions have used the classical rotation vector description. Although this description yields both the orientation of the head rotation axis and the amount of rotation, it is incomplete because it cannot specify the location of this rotation axis in space. The latter is of importance for a proper picture of the vestibular consequences of active head movements and has relevance for the problem of how the brain deals with the inherent kinematic redundancy of the multijoint head-neck system. With this in mind, we have extended the rotation vector description by applying the helical axes approach, which yields both the classical rotation vector as well as the location of the rotation axis in space. Subjects ( n = 7), whose head movements were recorded optically, were instructed to shift gaze naturally to targets in 12 different directions at an eccentricity of 40°. The results demonstrate that the axes for these head movements occupy consistently different spatial locations. For purely horizontal movements, the rotation axis is located near a point midway between the two ear canals. For gaze shifts in other directions, the rotation axes are located below the ear canals along two circles, one for movements with an upward component (up circle), the other (typically larger in size) for movements with a downward component (down circle). Purely vertical movement (up and down) axes were located on the lower pole of the up and down circles, respectively. It was found that both circles, the upper poles of which coincided, became larger in size as movement amplitude increased, which means that the axis location shifts to lower and more eccentric locations with respect to the skull for larger flexion and extension movements. Although this pattern could be recognized in most subjects, there were consistent intersubject differences in the absolute size of the circles, their increase with movement amplitude, and in the relative sizes of the up and down circles. Because multiple vertebrae are involved in head movements, there are theoretically many possibilities to execute a certain head movement. The differences in circle patterns among subjects indicate different strategies in resolving this kinematic redundancy problem, a fact that was not apparent from the classical rotation vector part of our description, which yielded a rather uniform picture. A simple model suggests that the downward shift of the location of the rotation axis requires a modulation in vestibulo-ocular reflex gain of ≤10% to maintain fixation of a near target during vertical head movement. The involvement of the otolith system in this process remains to be determined.
GABA-Induced Intrinsic Light-Scattering Changes Associated With Voltage-Sensitive Dye Signals in Embryonic Brain Stem Slices: Coupling of Depolarization and Cell Shrinkage
Authors: Momose-Sato Yoko , Sato Katsushige , Hirota Akihiko , Kamino Kohtaro
Published: December 2017

Momose-Sato, Yoko, Katsushige Sato, Akihiko Hirota, and Kohtaro Kamino. GABA-induced intrinsic light-scattering changes associated with voltage-sensitive dye signals in embryonic brain stem slices: coupling of depolarization and cell shrinkage. J. Neurophysiol. 79: 2208–2217, 1998. We have found new evidence for γ-aminobutyric acid (GABA)-induced intrinsic optical changes associated with a voltage-sensitive dye signal in the early embryonic chick brain stem slice. The slices were prepared from 8-day-old embryos, and they were stained with a voltage-sensitive dye (NK2761). Pressure ejection of GABA to one site within the preparation elicited optical changes. With 580-nm incident light, two components were identified in the GABA-induced optical change. The first component was wavelength dependent, whereas the second, slower change was independent of wavelength. Comparison with the known action spectrum of the dye indicates that the first component reflects a depolarization of the membrane and that the second, slow component is a light-scattering change resulting from cell shrinkage coupled with the depolarization. Similar optical changes also were induced by glycine, although the amplitude of both the first and second signals was much smaller than for GABA. The optical changes induced by GABA persisted in the presence of picrotoxin and 2-hydroxysaclofen, suggesting that these optical responses include a novel GABA response, which has been termed GABAD in our previous reports.
Role of Monkey Cerebellar Nuclei in Skill for Sequential Movement
Authors: Lu Xiaofeng , Hikosaka Okihide , Miyachi Shigehiro
Published: December 2017

Lu, Xiaofeng, Okihide Hikosaka, and Shigehiro Miyachi. Role of monkey cerebellar nuclei in skill for sequential movement. J. Neurophysiol. 79: 2245–2254, 1998. To examine whether the cerebellum is involved in learning and memory of visuomotor sequences, we trained two monkeys on a sequential button press task and inactivated different portions of the cerebellar nuclei by injecting a small amount of muscimol (γ-aminobutyric acid agonist). Before the injection experiments started, the monkeys had learned a set of sequences ( n = 21 and 12) extensively. After each injection, we had the monkeys perform the learned sequences and, in addition, learn new sequences. We found deficits in learning/memory by the injections into the dorsal and central part of the dentate nucleus. The number of errors increased significantly for the learned sequences but not for the new sequences. This effect was present only when the hand ipsilateral to the muscimol injection was used. Consistent with this result, anticipatory saccades, the occurrence of which is correlated closely with motor skill, also became less frequent particularly when the ipsilateral hand was used. No effect on learning/memory was observed after injections into the ventral or lateral parts of the dentate nucleus, interpositus nucleus, or fastigial nucleus. In contrast, hand movements became slower after ipsilateral injections at all of the injection sites. These results suggest that, among the cerebellar nuclei, the dentate nucleus, especially its dorsal and central regions, is related to the storage and/or retrieval of long-term memory for motor skill.
Development of Spontaneous Synaptic Transmission in the Rat Spinal Cord
Authors: Gao Bao-Xi , Cheng Gong , Ziskind-Conhaim Lea
Published: December 2017

Gao, Bao-Xi, Gong Cheng, and Lea Ziskind-Conhaim. Development of spontaneous synaptic transmission in the rat spinal cord. J. Neurophysiol. 79: 2277–2287, 1998. Dorsal root afferents form synaptic connections on motoneurons a few days after motoneuron clustering in the rat lumbar spinal cord, but frequent spontaneous synaptic potentials are detected only after birth. To increase our understanding of the mechanisms underlying the differentiation of synaptic transmission, we examined the developmental changes in properties of spontaneous synaptic transmission at early stages of synapse formation. Spontaneous postsynaptic currents (PSCs) and tetrodotoxin (TTX)-resistant miniature PSCs (mPSCs) were measured in spinal motoneurons of embryonic and postnatal rats using whole cell patch-clamp recordings. Spontaneous PSC frequencies were higher than mPSC frequencies in both embryonic and postnatal motoneurons, suggesting that even at embryonic stages, when action-potential firing rate was low, presynaptic action potentials played an important role in triggering spontaneous PSCs. After birth, the twofold increase in spontaneous PSC frequency was attributed to an increase in action-potential–independent quantal release rather than to a higher rate of action-potential firing. In embryonic motoneurons, the fluctuations in peak amplitude of spontaneous PSCs were normally distributed around single peaks with modal values similar to those of mPSCs. These data indicated that early in synapse differentiation spontaneous PSCs were primarily composed of currents generated by quantal release. After birth, mean mPSC amplitude increased by 50% but mean quantal current amplitude did not change. Synchronous, multiquantal release was apparent in postnatal motoneurons only in high-K+ extracellular solution. Comparison of the properties of miniature excitatory and inhibitory postsynaptic currents (mEPSCs and mIPSCs) demonstrated that mean mEPSC frequency was higher than mIPSC frequency, suggesting that either excitatory synapses outnumbered inhibitory synapses or that the probability of excitatory transmitter release was higher than the release of inhibitory neurotransmitters. The finding that mIPSC duration was several-fold longer than mEPSC duration implied that despite their lower frequency, inhibitory currents could modulate motoneuron synaptic integration by shunting incoming excitatory inputs for prolonged time intervals.
Activation Kinetics of the Delayed Rectifier Potassium Current of Bullfrog Sympathetic Neurons
Authors: Klemic Kathryn G. , Durand Dominique M. , Jones Stephen W.
Published: December 2017

Klemic, Kathryn G., Dominique M. Durand, and Stephen W. Jones. Activation kinetics of the delayed rectifier potassium current of bullfrog sympathetic neurons. J. Neurophysiol. 79: 2345–2357, 1998. We examined the activation kinetics of the delayed rectifier K+ current of bullfrog sympathetic neurons, primarily using whole cell recording. On depolarization, currents activated with a sigmoid delay but did not show a Cole-Moore shift. The time course of activation differed systematically from an exponential raised to a power. At most voltages, a power of 2 gave the best overall fit but a power of 3 better described the initial delay. After the delay, the time course could be fitted by a single exponential. Time constants were 15–20 ms at 0 mV and decreased to a limiting τ = 7 ms at +50 to +100 mV. Tail currents were well fitted by single exponential functions and accelerated with hyperpolarization, from τ = 15–20 ms at 0 mV to τ = 2 ms at −110 mV ( e-fold for 40 mV). Eleven kinetic models were evaluated for their ability to describe the activation kinetics of the delayed rectifier. Hodgkin-Huxley–like models did not fit the data well. A linear model where voltage sensor movement is followed by a distinct channel opening step, allosteric models based on the Monod-Wyman–Changeux model, and an unconstrained C-C-C-O model could describe whole cell data from −100 to +40 mV. After including whole cell data at +60 and +80 mV, and a maximal p open of 0.8 from noise analysis of cell-attached patches, an allosteric model fit the data best, as the other models had difficulty describing qualitative features of the data. However, some more complex schemes (with additional free parameters) cannot be excluded. We propose the allosteric model as an empirical description of macroscopic ionic currents, and as a model worth considering in future studies on the molecular mechanism of potassium channel gating.
Picrotoxin Eliminates Frequency Selectivity of an Auditory Interneuron in a Bushcricket
Authors: Stumpner Andreas
Published: December 2017

Stumpner, Andreas. Picrotoxin eliminates frequency selectivity of an auditory interneuron in a bushcricket. J. Neurophysiol. 79: 2408–2415, 1998. AN1, an auditory interneuron in the bushcricket Ancistrura nigrovittata, is narrowly tuned to the male song frequency (∼15 kHz). It receives pronounced inhibitory input at frequencies below and, more prominently, above this fundamental frequency. It is also subject to side-dependent inhibition producing asymmetric response functions for left- and right-side stimulation. In addition, intensity-response functions of AN1 peak as stimulus intensities increase. Application of the GABAAchannel-blocker picrotoxin eliminates all subthreshold inhibitory postsynaptic potentials, revealing underlying excitation that is particularly obvious in the high-frequency range. Excitatory thresholds close to the song frequency remain unchanged by picrotoxin. Thus a specifically tuned neuron is shown to become broadly tuned after elimination of frequency-dependent inhibition. Although average maximum response strength is increased by 150% after picrotoxin application, at male song frequencies a slight reduction of the responses is still present at high intensities. Side-dependent inhibition remains largely unaffected by picrotoxin, suggesting that side- and frequency-dependent inhibitions are caused by different transmitters from different neurons.