bluuebunny/crossref_metadata_2025 huggingface dataset:
Role of the Subthalamic Nucleus in Cannabinoid Actions in the Substantia Nigra of the Rat
Authors: Sañudo-Peña M. Clara , Walker J. Michael
Published: December 2017

Sañudo-Peña, M. Clara and J. Michael Walker. Role of the subthalamic nucleus in cannabinoid actions in the substantia nigra of the rat. J. Neurophysiol. 77: 1635–1638, 1997. The effect of cannabinoids on the excitatory input to the substantia nigra reticulata (SNr) from the subthalamic nucleus was explored. For this purpose a knife cut was performed rostral to the subthalamic nucleus to isolate the subthalamic nucleus and the SNr from the striatum, a major source of cannabinoid receptors to the SNr. The data showed that the cannabinoid agonist WIN55,212-2 blocked the increase in the firing rate of SNr neurons induced by stimulation of the subthalamic nucleus with bicuculline. Furthermore, the cannabinoid antagonist SR141716A antagonized the effect of the cannabinoid agonist. This study showed that cannabinoids regulate not only the striatonigral pathway, as previously reported, but also the subthalamonigral pathway. The opposite influences of these two inputs to the SNr, inhibitory and excitatory respectively, suggest that endogenous cannabinoids play a major role in the physiological regulation of the SNr.
Contribution of Voltage-Gated Ca2+ Channels to Homosynaptic Long-Term Depression in the CA1 Region In Vitro
Authors: Christie Brian R. , Schexnayder Lalania K. , Johnston Daniel
Published: December 2017

Christie, Brian R., Lalania K. Schexnayder, and Daniel Johnston. Contribution of voltage-gated Ca2+ channels to homosynaptic long-term depression in the CA1 region in vitro. J. Neurophysiol. 77: 1651–1655, 1997. Homosynaptic long-term depression (LTD) of synaptic efficacy was induced in field excitatory postsynaptic potentials by administration of 900 pulses at either 1 or 3 Hz in 2- to 3-wk-old Sprague-Dawley rats. The stimulation was administered via a bipolar stimulating electrode placed immediately adjacent to the recording electrode in the stratum radiatum region of the hippocampal CA1 subfield. Equivalent LTD induction occurred whether the slices were maintained at room temperature or at 32°C. Lowering bath Ca2+ to 0 mM, or increasing it to 4 mM, prevented the induction of the depression. The NMDA receptor antagonist d,l-2-amino-5-phosphonovaleric acid (50 μM) reversibly blocked the induction of homosynaptic LTD. In addition, the L-type voltage-gated calcium channel (VGCC) antagonist nimodipine (10 μM) and the R- and T-type VGCC antagonist NiCl2 (25 μM) also prevented homosynaptic LTD induction. These results indicate that in addition to N-methyl-d-aspartate receptor activity, Ca2+ influx via VGCCs can play an important role in the induction and expression of LTD induced by low-frequency stimulation in the hippocampal formation.
Dynamic Interactions Determine Partial Thalamic Quiescence in a Computer Network Model of Spike-and-Wave Seizures
Authors: Lytton William W. , Contreras Diego , Destexhe Alain , Steriade Mircea
Published: December 2017

Lytton, William W., Diego Contreras, Alain Destexhe, and Mircea Steriade. Dynamic interactions determine partial thalamic quiescence in a computer network model of spike-and-wave seizures. J. Neurophysiol. 77: 1679–1696, 1997. In vivo intracellular recording from cat thalamus and cortex was performed during spontaneous spike-wave seizures characterized by synchronously firing cortical neurons correlated with the electroencephalogram. During these seizures, thalamic reticular (RE) neurons discharged with long spike bursts riding on a depolarization, whereas thalamocortical (TC) neurons were either entrained into the seizures (40%) or were quiescent (60%). During quiescence, TC neurons showed phasic inhibitory postsynaptic potentials (IPSPs) that coincided with paroxysmal depolarizing shifts in the simultaneously recorded cortical neuron. Computer simulations of a reciprocally connected TC-RE pair showed two major modes of TC-RE interaction. In one mode, a mutual oscillation involved direct TC neuron excitation of the RE neuron leading to a burst that fed back an IPSP into the TC neuron, producing a low-threshold spike. In the other, quiescent mode, the TC neuron was subject to stronger coalescing IPSPs. Simulated cortical stimulation could trigger a transition between the two modes. This transition could go in either direction and was dependent on the precise timing of the input. The transition did not always follow the stimulation immediately. A larger, multicolumnar simulation was set up to assess the role of the TC-RE pair in the context of extensive divergence and convergence. The amount of TC neuron spiking generally correlated with the strength of total inhibitory input, but large variations in the amount of spiking could be seen. Evidence for mutual oscillation could be demonstrated by comparing TC neuron firing with that in reciprocally connected RE neurons. An additional mechanism for TC neuron quiescence was assessed with the use of a cooperative model of γ-aminobutyric acid-B (GABAB)-mediated responses. With this model, RE neurons receiving repeated strong excitatory input produced TC neuron quiescence due to burst-duration-associated augmentation of GABAB current. We predict the existence of spatial inhomogeneity in apparently generalized spike-wave seizures, involving a center-surround pattern. In the center, intense cortical and RE neuron activity would be associated with TC neuron quiescence. In the surround, less intense hyperpolarization of TC neurons would allow low-threshold spikes to occur. This surround, an “epileptic penumbra,” would be the forefront of the expanding epileptic wave during the process of initial seizure generalization. Therapeutically, we would then predict that agents that reduce TC neuron activity would have a greater effect on seizure onset than on ongoing spike-wave seizures or other thalamic oscillations.
Spontaneous Subthreshold Membrane Potential Fluctuations and Action Potential Variability of Rat Corticostriatal and Striatal Neurons In Vivo
Authors: Stern Edward A. , Kincaid Anthony E. , Wilson Charles J.
Published: December 2017

Stern, Edward A., Anthony E. Kincaid, and Charles J. Wilson. Spontaneous subthreshold membrane potential fluctuations and action potential variability of rat corticostriatal and striatal neurons in vivo. J. Neurophysiol. 77: 1697–1715, 1997. We measured the timing of spontaneous membrane potential fluctuations and action potentials of medial and lateral agranular corticostriatal and striatal neurons with the use of in vivo intracellular recordings in urethan-anesthetized rats. All neurons showed spontaneous subthreshold membrane potential shifts from 7 to 32 mV in amplitude, fluctuating between a hyperpolarized down state and depolarized up state. Action potentials arose only during the up state. The membrane potential state transitions showed a weak periodicity with a peak frequency near 1 Hz. The peak of the frequency spectra was broad in all neurons, indicating that the membrane potential fluctuations were not dominated by a single periodic function. At frequencies >1 Hz, the log of magnitude decreased linearly with the log of frequency in all neurons. No serial dependence was found for up and down state durations, or for the time between successive up or down state transitions, showing that the up and down state transitions are not due to superimposition of noisy inputs onto a single frequency. Monte Carlo simulations of stochastic synaptic inputs to a uniform finite cylinder showed that the Fourier spectra obtained for corticostriatal and striatal neurons are inconsistent with a Poisson-like synaptic input, demonstrating that the up state is not due to an increase in the strength of an unpatterned synaptic input. Frequency components arising from state transitions were separated from those arising from the smaller membrane potential fluctuations within each state. A larger proportion of the total signal was represented by the fluctuations within states, especially in the up state, than was predicted by the simulations. The individual state spectra did not correspond to those of random synaptic inputs, but reproduced the spectra of the up and down state transitions. This suggests that the process causing the state transitions and the process responsible for synaptic input may be the same. A high-frequency periodic component in the up states was found in the majority of the corticostriatal cells in the sample. The average size of the component was not different between neurons injected with QX-314 and control neurons. The high-frequency component was not seen in any of our sample of striatal cells. Corticostriatal and striatal neurons' coefficients of variation of interspike intervals ranged from 1.0 to 1.9. When interspike intervals including a down state were subtracted from the calculation, the coefficient of variation ranged from 0.4 to 1.1, indicating that a substantial proportion of spike interval variance was due to the subthreshold membrane potential fluctuations.
Dynamics of Neurons Controlling Movements of a Locust Hind Leg II. Flexor Tibiae Motor Neurons
Authors: Newland Philip L. , Kondoh Yasuhiro
Published: December 2017

Newland, Philip L. and Yasuhiro Kondoh. Dynamics of neurons controlling movements of a locust hind leg. II. Flexor tibiae motor neurons. J. Neurophysiol. 77: 1731–1746, 1997. Imposed movements of a proprioceptor that monitors the relative position of the tibia about the femur, the femorotibial chordotonal organ (FeCO), evoke resistance reflexes in the motor neurons that control the movements of the tibia of the locust. The response dynamics of one pool of motor neurons, the flexor tibiae motor neurons, which are located in three groups (anterior, lateral, and posterior), have been analyzed by the Wiener kernel method. First- and second-order kernels that represent the linear and nonlinear responses, respectively, were computed by a cross-correlation between the intracellularly recorded synaptic responses in the motor neurons and the white noise stimulus applied to the FeCO, and were used to define the input-output characteristics of the motor neurons. The posterior fast, intermediate, and slow and the anterior fast and intermediate flexor tibiae motor neurons had biphasic first-order kernels with initial negative phases, indicating that they are velocity sensitive. The falling phases of the kernels had distinct shoulders, indicating that the responses of the motor neurons also had delayed low-pass components, i.e., position sensitivity. The anterior slow flexor motor neuron had a monophasic, low-passed, first-order kernel, indicating that it is position sensitive. The linear component of the motor neuron responses, predicted by convolving the first-order kernels with the stimulus signal, strongly resembled the actual response, whereas the second-order nonlinear component was small, particularly at >10 Hz. The power spectra of the fast motor neurons showed that they had the highest cutoff frequencies (at >8 Hz), whereas the slow flexor motor neurons had a gradual roll-off at 1 Hz. The intermediate flexor motor neuron had an intermediate cutoff frequency of ∼2–3 Hz. The linear responses of the flexor motor neurons could be decomposed into low- and high-frequency components. The high-frequency components (>10 Hz) were velocity dependent and linear, whereas the low-frequency components (<10 Hz) were position dependent and nonlinear. The nonlinearity was a signal compression (or half-wave rectification). The results show that although the flexor motor neurons receive many common inputs during FeCO stimulation, each individual has specific dynamic response properties. The responses of the motor neurons are fractionated so that a given individual within the pool will respond best to position, whereas others will respond better to velocity. Likewise, some motor neurons respond best at low frequencies, whereas others respond best at higher frequencies of stimulation.
Calcium Channel Currents in Acutely Dissociated Intracardiac Neurons From Adult Rats
Authors: Jeong Seong-Woo , Wurster Robert D.
Published: December 2017

Jeong, Seong-Woo and Robert D. Wurster. Calcium channel currents in acutely dissociated intracardiac neurons from adult rats. J. Neurophysiol. 77: 1769–1778, 1997. With the use of the whole cell patch-clamp technique, multiple subtypes of voltage-activated calcium channels, as indicated by measuring Ba2+ currents, were pharmacologically identified in acutely dissociated intracardiac neurons from adult rats. All tested neurons that were held at −80 mV displayed only high-voltage-activated (HVA) Ca2+ channel currents that were completely blocked by 100 μM CdCl2. The current density of HVA Ca2+ currents was dependent on the external Ca2+ concentration. The Ba2+ (5 mM) currents were half-activated at −16.3 mV with a slope of 5.6 mV per e-fold change. The steady-state inactivation was also voltage dependent with half-inactivation at −33.7 mV and a slope of −12.1 mV per e-fold change. The most effective L-type channel activator, FPL 64176 (2 μM), enhanced the Ba2+ current in a voltage-dependent manner. When cells were held at −80 mV, the saturating concentration (10 μM) of nifedipine blocked ∼11% of the control Ba2+ current. The major component of the Ca2+ channels was N type (63%), which was blocked by a saturating concentration (1 μM) of ω-conotoxin GVIA. Approximately 19% of the control Ba2+ current was sensitive to ω-conotoxin MVIIC (5 μM) but insensitive to low concentrations (30 and 100 nM) of ω-agatoxin IVA (ω-Aga IVA). In addition, a high concentration (1 μM) of ω-Aga IVA occluded the effect of ω-conotoxin MVIIC. Taken together, these results indicate that the ω-conotoxin MVIIC-sensitive current represents only the Q type of Ca2+ channels. The current that was insensitive to nifedipine and various toxins represents the R-type current (7%), which was sensitive to 100 μM NiCl2. In conclusion, the intracardiac neurons from adult rats express at least four different subtypes (L, N, Q, and R) of HVA Ca2+ channels. This information is essential for understanding the regulation of synaptic transmission and excitability of intracardiac neurons by different neurotransmitters and neural regulation of cardiac functions.
Muscarinic Modulation of the Oscillatory and Repetitive Firing Properties of Entorhinal Cortex Layer II Neurons
Authors: Klink Ruby , Alonso Angel
Published: December 2017

Klink, Ruby and Angel Alonso. Muscarinic modulation of the oscillatory and repetitive firing properties of entorhinal cortex layer II neurons. J. Neurophysiol. 77: 1813–1828, 1997. Neurons in layer II of the entorhinal cortex (EC) are key elements in the temporal lobe memory system because they integrate and transfer into the hippocampal formation convergent sensory input from the entire cortical mantle. EC layer II also receives a profuse cholinergic innervation from the basal forebrain that promotes oscillatory dynamics in the EC network and may also implement memory function. To understand the cellular basis of cholinergic actions in EC, we investigated by intracellular recording in an in vitro rat brain slice preparation the muscarinic modulation of the electroresponsive properties of the two distinct classes of medial EC layer II projection neurons, the stellate cells (SCs) and non-SCs. In both SCs and non-SCs, muscarinic receptor activation with carbachol (CCh, 10–50 μM) caused atropine-sensitive (300 nM) membrane depolarization. In SCs, the CCh-induced membrane depolarization was associated with subthreshold membrane potential oscillations and “spike cluster” discharge, which are typically expressed by these cells on depolarization. CCh, however, caused a decrease of the dominant frequency of the membrane potential oscillations from 9.2 ± 1.1 (SD) Hz to 6.3 ± 1.1 Hz, as well as a decrease of the intracluster firing frequency from 18.1 ± 1.7 Hz to 13.6 ± 1.3 Hz. In addition, spike cluster discharge was less robust, and the cells tended to shift into tonic firing during CCh. In contrast to SCs, in non-SCs, CCh drastically affected firing behavior by promoting the development of voltage-dependent, long-duration (1–5 s) slow bursts of action potentials that could repeat rhythmically at slow frequencies (0.2–0.5 Hz). Concomitantly, the slow afterhyperpolarization (sAHP) was replaced by long-lasting plateau postdepolarizations. In both SCs and non-SCs, CCh also produced conspicuous changes on the action potential waveform and its afterpotentials. Notably, CCh significantly decreased spike amplitude and rate of rise, which suggests muscarinic modulation of a voltage-dependent Na+ conductance. Finally, we also observed that whereas CCh abolished the sAHP in both SCs and non-SCs, the membrane-permeant analogues of adenosine 3′,5′-cyclic monophosphate, 8-(4-chlorophenylthio)-adenosine-cyclic monophosphate and 8-bromo-adenosine-cyclic-monophosphate, abolished the sAHP in SCs but not in non-SCs. The data demonstrate that cholinergic modulation further differentiates the intrinsic electroresponsiveness of SCs and non-SCs, and add support to the presence of two parallel processing systems in medial EC layer II that could thereby differentially influence their hippocampal targets. The results also indicate an important role for the cholinergic system in tuning the oscillatory dynamics of entorhinal neurons.
GABA- and Glycine-Mediated Fall of Intracellular pH in Rat Medullary Neurons In Situ
Authors: Lückermann Mark , Trapp Stefan , Ballanyi Klaus
Published: December 2017

Lückermann, Mark, Stefan Trapp, and Klaus Ballanyi. GABA- and glycine-mediated fall of intracellular pH in rat medullary neurons in situ. J. Neurophysiol. 77: 1844–1852, 1997. In the region of the ventral respiratory group in brain stem slices from neonatal rats, intracellular pH (pHi) and membrane currents ( Im) or potentials were measured in neurons dialyzed with the pH-sensitive dye 2′,7′-bis-carboxyethyl-5(6)-carboxyfluorescein. Currents and increases in membrane conductance ( gm) during bath application of 0.1 or 1 mM γ-aminobutyric acid (GABA) were accompanied by a delayed mean fall of pHiby 0.17 and 0.25 pH units, respectively, from a pHibaseline of 7.33. These effects were reversibly suppressed by 50–100 μM bicuculline. Similar effects on Im, gm, and pHiwere revealed on administration of 0.1 or 1 mM glycine. These responses were abolished by 10–100 μM strychnine. Dialysis of the cells with 15–30 μM carbonic anhydrase led to an acceleration of the kinetics and a potentiation of the GABA-induced pHidecrease. GABA- and glycine-evoked pHidecreases were very similar during recordings with either high- or low-Cl−patch electrodes, although the reversal potential of the accompanying currents differed by ∼60 mV. The GABA-induced pHidecrease, but not the accompanying Imand gmresponses, was suppressed in CO2/HCO−3-free, N-2-hydroxy-ethylpiperazine- N′-2-ethane sulphonic acid pH-buffered solution. Depolarization from −60 to +30 mV resulted in a sustained fall of pHiby maximally 0.5 pH units. In this situation, the GABA-induced fall of pHiturned into an intracellular alkalosis of 0.09–0.15 pH units. The results confirm and extend previous findings obtained in vivo that GABA- or glycine-induced intracellular acidosis of respiratory neurons is due to efflux of HCO−3via the receptor-coupled Cl−channel.
Ionic Basis of Learning-Correlated Excitability Changes in Hermissenda Type A Photoreceptors
Authors: Farley Joseph , Han Yunru
Published: December 2017

Farley, Joseph and Yunru Han. Ionic basis of learning-correlated excitability changes in Hermissenda type A photoreceptors. J. Neurophysiol. 77: 1861–1888, 1997. Repeated pairings of light and rotation (conditioning) result in persistent changes in excitability of Hermissenda type B and A photoreceptors, which are correlated with pairing-specific reductions in phototactic behavior. Although considerable attention has been devoted to characterization of conditioning-produced neurophysiological changes that occur in type B cells, less information is available concerning the changes produced in type A cells. Here we recorded from identified, synaptically isolated lateral and medial type A photoreceptors from conditioned, random-control, or untrained animals on retention days following conditioning. Type A photoreceptors from conditioned animals responded to light with a receptor potential that was significantly smaller than those of random-control or untrained animals, which did not differ. The phototactic suppression and type A cell light response magnitudes were negatively correlated for individual conditioned animals. Animals exhibiting strong phototactic suppression also showed small light responses. Expression of the training-associated light response difference was a calcium-dependent phenomenon: reducing extracellular calcium to <1 μM enhanced the generator potential of A cells, regardless of conditioning history, and greatly reduced the differences in generator potential amplitude attributable to training. Voltage-clamp studies revealed that conditioning resulted in a two- to threefold increase in the amplitude of a voltage-dependent, sustained outward K+ current ( I Delayed). I Delayed magnitudes were positively correlated with phototactic suppression for individual conditioned animals: type A cells of animals exhibiting strong phototactic suppression expressed large values of I Delayed. I Delayed is a composite current, consisting of at least three separable components: 1) residual A current ( I A); 2) slow, tetraethylammonium-sensitive calcium-activated K+ current ( I K-Ca); and 3) a delayed-rectifier-type, voltage-dependent K+ current ( I K,v). Analysis of these currents failed to reveal significant training-associated changes in I A or I K-Ca. But I K,v was enhanced by ∼60–150% in both lateral and medial cells and thus contributes to the conditioning-associated increase in I Delayed.
Blocking GABAA Inhibition Reveals AMPA- and NMDA-Receptor-Mediated Polysynaptic Responses in the CA1 Region of the Rat Hippocampus
Authors: Crépel V. , Khazipov R. , Ben-Ari Y.
Published: December 2017

Crépel, V., R. Khazipov, and Y. Ben-Ari. Blocking GABAA inhibition reveals AMPA- and NMDA-receptor-mediated polysynaptic responses in the CA1 region of the rat hippocampus. J. Neurophysiol. 77: 2071–2082, 1997. We have investigated the conditions required to evoke polysynaptic responses in the isolated CA1 region of hippocampal slices from Wistar adult rats. Experiments were performed with extracellular and whole cell recording techniques. In the presence of bicuculline (10 μM), 6-cyano-7-nitroquinoxaline-2-3-dione (10 μM), glycine (10 μM), and a low external concentration of Mg2+ (0.3 mM), electrical stimulation of the Schaffer collaterals/commissural pathway evoked graded N-methyl-d-aspartate (NMDA)-receptor-mediated late field potentials in the stratum radiatum of the CA1 region. These responses were generated via polysynaptic connections because their latency varied strongly and inversely with the stimulation intensity and they were abolished by a high concentration of divalent cations (7 mM Ca2+). These responses likely were driven by local collateral branches of CA1 pyramidal cell axons because focal application of tetrodotoxin (30 μM) in the stratum oriens strongly reduced the late synaptic component and antidromic stimulation of CA1 pyramidal cells could evoke the polysynaptic response. Current-source density analysis suggested that the polysynaptic response was generated along the proximal part of the apical dendrites of CA1 pyramidal cells (50–150 μm below the pyramidal cell layer in the stratum radiatum). In physiological concentration of Mg2+ (1.3 mM), the pharmacologically isolated NMDA-receptor-mediated polysynaptic response was abolished. In control artificial cerebrospinal fluid (with physiological concentration of Mg2+), bicuculline (10 μM) generated a graded polysynaptic response. Under these conditions, this response was mediated both by α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA)/NMDA receptors. In the presence of d-2-amino-5-phosphonovalerate (50 μM), the polysynaptic response could be mediated by AMPA receptors, although less efficiently. In conclusion, suppression of γ-aminobutyric acid-A inhibition reveals glutamate receptor-mediated network-driven events in the isolated CA1 region. These polysynaptic responses are mediated by AMPA and/or NMDA receptors depending on the pharmacological conditions and the external concentration of Mg2+ used. We suggest that these responses are driven by local recurrent collaterals of CA1 pyramidal cells.
Marginal Shell of the Anteroventral Cochlear Nucleus: Single-Unit Response Properties in the Unanesthetized Decerebrate Cat
Authors: Ghoshal S. , Kim D. O.
Published: December 2017

Ghoshal, S. and D. O. Kim. Marginal shell of the anteroventral cochlear nucleus: single-unit response properties in the unanesthetized decerebrate cat. J. Neurophysiol. 77: 2083–2097, 1997. The marginal shell of the anteroventral cochlear nucleus (AVCN) is anatomically different from its central core. We investigated 38 single units in the shells of 10 cats and contrasted them with 62 single units in the cores of 15 cats. The sites of all shell units were localized with the use of reconstructed electrode tracks. The shell units were divided into acoustically well-driven (68%) and weakly/not-driven (32%) subgroups. The shell units mostly exhibited low spontaneous rates (SRs). Among the well-driven shell units, a large majority (68%) exhibited wide dynamic ranges (≥50 dB) to tones, noise, or both, with some ranges as wide as 89 dB. In contrast, a large majority (80%) of the core units exhibited narrow dynamic ranges (<50 dB) to tones and noise. The poststimulus time histograms (PSTHs) of the well-driven shell units included pause-build (29%), onset (24%), and unusual (33%) types, whereas those of the core units included mainly primary-like (47%) and chopper (29%) types. The excitatory-inhibitory areas (EIAs) of the well-driven shell units included types I/III (47%), III (22%), IV (13%), and II (9%), whereas those of the core units included mainly types III (52%) and I/III (32%). On the basis of Fisher's exact tests, we conclude that the shell and core neural groups of the AVCN are significantly different regarding all of the following physiological characteristics: SR, maximum driven rate, threshold and dynamic range to tones and noise, frequency response area, PSTH type, latency, and EIA type. Wide dynamic ranges of the well-driven shell units suggest that they may play a role in encoding absolute intensity of acoustic stimulus.
Activation on the Medial Wall During Remembered Sequences of Reaching Movements in Monkeys
Authors: Picard Nathalie , Strick Peter L.
Published: December 2017

Picard, Nathalie and Peter L. Strick. Activation on the medial wall during remembered sequences of reaching movements in monkeys. J. Neurophysiol. 77: 2197–2201, 1997. We used the 2-deoxyglucose (2DG) method to map activation in the motor areas on the medial wall of the hemisphere. One group of monkeys licked juice delivered at variable time intervals (LICK task). For these animals, the motor areas on the medial wall displayed restricted activation. 2DG uptake was limited largely to the face representation of the supplementary motor area (SMA). Additional labeling was present more rostrally in the banks of the cingulate sulcus. A second group of animals performed remembered sequences of reaching movements (REM task) for juice rewards. Activation related to licking also was present in this group. In addition, separate, discrete activations were found on the superior frontal gyrus and in the cingulate sulcus during the REM task. The most intense and extensive 2DG labeling was located in the dorsal bank of the cingulate sulcus, coincident with the dorsal cingulate motor area (CMAd). Weaker activations were present in the arm area of the SMA and in the pre-SMA. There was no significant 2DG incorporation in the ventral bank of the cingulate sulcus where the ventral cingulate motor area is located. Our findings suggest that the CMAd is involved more than any other medial area in the preparation for and/or execution of highly practiced, remembered sequences of movements. Overall, our results indicate that the attributes of motor control are not represented equally across the motor areas on the medial wall.
Binary Mapping of Cortical Spike Trains in Short-Term Memory
Authors: Bodner Mark , Zhou Yong-Di , Fuster Joaquín M.
Published: December 2017

Bodner, Mark, Yong-Di Zhou, and Joaquı́n M. Fuster. Binary mapping of cortical spike trains in short-term memory. J. Neurophysiol. 77: 2219–2222, 1997. Microelectrode studies in monkeys performing short-term memory tasks show the sustained elevated discharge of cortical neurons during the retention of recalled sensory information. Cortical cells that are part of memory networks are assumed to receive numerous inputs of excitatory as well as inhibitory nature and local as well as remote. Thus it is reasonable to postulate that the temporal and spatial summation of diverse inputs on any cell in an activated network will result in temporally discrete groups of spikes in its firing. The activation of a network in active memory supposedly increases the magnitude and diversity of those inputs and thus increases the discontinuities and frequency fluctuations in the firing of cells in the network. In this study we use a new method of analysis that allows the quantification of firing discontinuities in a spike train. We apply it to parietal cells recorded from monkeys during the performance of a tactile short-term memory task. In our method, time is divided into bins of equal duration and the measure of discontinuities is the total count of the number of transitions between consecutive time bins with and without spikes. The results of the analysis show that in many of the cells studied, discontinuities (transitions between spiking and nonspiking) reflect memory-related activity obscured in the measures of raw spike frequency over a wide range of frequencies. These cells show more firing transitions in active short-term memory than in baseline (intertrial) conditions.
Psychophysical and Physiological Evidence for a Precedence Effect in the Median Sagittal Plane
Authors: Litovsky Ruth Y. , Rakerd Brad , Yin Tom C. T. , Hartmann William M.
Published: December 2017

Litovsky, Ruth Y., Brad Rakerd, Tom C. T. Yin, and William M. Hartmann. Psychophysical and physiological evidence for a precedence effect in the median sagittal plane. J. Neurophysiol. 77: 2223–2226, 1997. A listener in a room is exposed to multiple versions of any acoustical event, coming from many different directions in space. The precedence effect is thought to discount the reflected sounds in the computation of location, so that a listener perceives the source near its true location. According to most auditory theories, the precedence effect is mediated by binaural differences. This report presents evidence that the precedence effect operates in the median sagittal plane, where binaural differences are virtually absent and where spectral cues provide information regarding the location of sounds. Parallel studies were conducted in psychophysics by measuring human listeners' performance, and in neurophysiology by measuring responses of single neurons in the inferior colliculus of cats. In both experiments the precedence effect was found to operate similarly in the azimuthal and sagittal planes. It is concluded that precedence is mediated by binaurally based and spectrally based localization cues in the azimuthal and sagittal planes, respectively. Thus,models that attribute the precedence effect entirely to processes that involve binaural differences are no longer viable.
Suppression of Task-Related Saccades by Electrical Stimulation in the Primate's Frontal Eye Field
Authors: Burman Douglas D. , Bruce Charles J.
Published: December 2017

Burman, Douglas D. and Charles J. Bruce. Suppression of task-related saccades by electrical stimulation in the primate's frontal eye field. J. Neurophysiol. 77: 2252–2267, 1997. Patients with frontal lobe damage have difficulty suppressing reflexive saccades to salient visual stimuli, indicating that frontal lobe neocortex helps to suppress saccades as well as to produce them. In the present study, a role for the frontal eye field (FEF) in suppressing saccades was demonstrated in macaque monkeys by application of intracortical microstimulation during the performance of a visually guided saccade task, a memory prosaccade task, and a memory antisaccade task. A train of low-intensity (20–50 μA) electrical pulses was applied simultaneously with the disappearance of a central fixation target, which was always the cue to initiate a saccade. Trials with and without stimulation were compared, and significantly longer saccade latencies on stimulation trials were considered evidence of suppression. Low-intensity stimulation suppressed task-related saccades at 30 of 77 sites tested. In many cases saccades were suppressed throughout the microstimulation period (usually 450 ms) and then executed shortly after the train ended. Memory-guided saccades were most dramatically suppressed and were often rendered hypometric, whereas visually guided saccades were less severely suppressed by stimulation. At 18 FEF sites, the suppression of saccades was the only observable effect of electrical stimulation. Contraversive saccades were usually more strongly suppressed than ipsiversive ones, and cells recorded at such purely suppressive sites commonly had either foveal receptive fields or postsaccadic responses. At 12 other FEF sites at which saccadic eye movements were elicited at low thresholds, task-related saccades whose vectors differed from that of the electrically elicited saccade were suppressed by electrical stimulation. Such suppression at saccade sites was observed even with currents below the threshold for eliciting saccades. Pure suppression sites tended to be located near or in the fundus, deeper in the anterior bank of the arcuate than elicited saccade sites. Stimulation in the prefrontal association cortex anterior to FEF did not suppress saccades, nor did stimulation in premotor cortex posterior to FEF. These findings indicate that the primate FEF can help orchestrate saccadic eye movements by suppressing inappropriate saccade vectors as well as by selecting, specifying, and triggering appropriate saccades. We hypothesize that saccades could be suppressed both through local FEF interactions and through FEF projections to subcortical regions involved in maintaining fixation.
Eye-Head Coordination During Head-Unrestrained Gaze Shifts in Rhesus Monkeys
Authors: Freedman Edward G. , Sparks David L.
Published: December 2017

Freedman, Edward G. and David L. Sparks. Eye-head coordination during head-unrestrained gaze shifts in rhesus monkeys. J. Neurophysiol. 77: 2328–2348, 1997. We analyzed gaze shifts made by trained rhesus monkeys with completely unrestrained heads during performance of a delayed gaze shift task. Subjects made horizontal, vertical, and oblique gaze shifts to visual targets. We found that coordinated eye-head movements are characterized by a set of lawful relationships, and that the initial position of the eyes in the orbits and the direction of the gaze shift are two factors that influence these relationships. Head movements did not contribute to the change in gaze position during small gaze shifts (<20°) directed along the horizontal meridian, when the eyes were initially centered in the orbits. For larger gaze shifts (25–90°), the head contribution to the gaze shift increased linearly with increasing gaze shift amplitude, and eye movement amplitude saturated at an asymptotic amplitude of ∼35°. When the eyes began deviated in the orbits contralateral to the direction of the ensuing gaze shift, the head contributed less and the eyes more to amplitude-matched gaze shifts. The relative timing of eye and head movements was altered by initial eye position; head latency relative to gaze onset increased as the eyes began in more contralateral initial positions. The direction of the gaze shift also affected the relative amplitudes of eye and head movements; as gaze shifts were made in progressively more vertical directions, eye amplitude increased and head contribution declined systematically. Eye velocity was a saturating function of gaze amplitude for movements without a head contribution (gaze amplitude <20°). As head contribution increased with increasing gaze amplitude (20–60°), peak eye velocity declined by >200°/s and head velocity increased by 100°/s. For constant-amplitude eye movements (∼30°), eye velocity declined as the velocity of the concurrent head movement increased. On the basis of these relationships, it is possible to accurately predict gaze amplitude, the amplitudes of the eye and head components of the gaze shift, and gaze, eye, and head velocities, durations and latencies if the two-dimensional displacement of the target and the initial position of the eyes in the orbits are known. These data indicate that signals related to the initial positions of the eyes in the orbits and the direction of the gaze shift influence separate eye and head movement commands. The hypothesis that this divergence of eye and head commands occurs downstream from the superior colliculus is supported by recent electrical stimulation and single-unit recording data.
Fast and Slow Activation Kinetics of Voltage-Gated Sodium Channels in Molluscan Neurons
Authors: Gilly William F. , Gillette Rhanor , McFarlane Matthew
Published: December 2017

Gilly, William F., Rhanor Gillette, and Matthew McFarlane. Fast and slow activation kinetics of voltage-gated sodium channels in molluscan neurons. J. Neurophysiol. 77: 2373–2384, 1997. Whole cell patch-clamp recordings of Na current ( INa) were made under identical experimental conditions from isolated neurons from cephalopod ( Loligo, Octopus) and gastropod ( Aplysia, Pleurobranchaea, Doriopsilla) species to compare properties of activation gating. Voltage dependence of peak Na conductance ( gNa) is very similar in all cases, but activation kinetics in the gastropod neurons studied are markedly slower. Kinetic differences are very pronounced only over the voltage range spanned by the gNa-voltage relation. At positive and negative extremes of voltage, activation and deactivation kinetics of INaare practically indistinguishable in all species studied. Voltage-dependent rate constants underlying activation of the slow type of Na channel found in gastropods thus appear to be much more voltage dependent than are the equivalent rates in the universally fast type of channel that predominates in cephalopods. Voltage dependence of inactivation kinetics shows a similar pattern and is representative of activation kinetics for the two types of Na channels. Neurons with fast Na channels can thus make much more rapid adjustments in the number of open Na channels at physiologically relevant voltages than would be possible with only slow Na channels. This capability appears to be an adaptation that is highly evolved in cephalopods, which are well known for their high-speed swimming behaviors. Similarities in slow and fast Na channel subtypes in molluscan and mammalian neurons are discussed.
Effects on Muscle Activity From Microstimuli Applied to Somatosensory and Motor Cortex During Voluntary Movement in the Monkey
Authors: Widener Gail L. , Cheney Paul D.
Published: December 2017

Widener, Gail L. and Paul D. Cheney. Effects on muscle activity from microstimuli applied to somatosensory and motor cortex during voluntary movement in the monkey. J. Neurophysiol. 77: 2446–2465, 1997. It is well known that electrical stimulation of primary somatosensory cortex (SI) evokes movements that resemble those evoked from primary motor cortex. These findings have led to the concept that SI may possess motor capabilities paralleling those of motor cortex and speculation that SI could function as a robust relay mediating motor responses from central and peripheral inputs. The purpose of this study was to rigorously examine the motor output capabilities of SI areas with the use of the techniques of spike- and stimulus-triggered averaging of electromyographic (EMG) activity in awake monkeys. Unit recordings were obtained from primary motor cortex and SI areas 3a, 3b, 1, and 2 in three rhesus monkeys. Spike-triggered averaging was used to assess the output linkage between individual cells and motoneurons of the recorded muscles. Cells in motor cortex producing postspike facilitation (PSpF) in spike-triggered averages of rectified EMG activity were designated corticomotoneuronal (CM) cells. Motor output efficacy was also assessed by applying stimuli through the microelectrode and computing stimulus-triggered averages of rectified EMG activity. One hundred seventy-one sites in motor cortex and 68 sites in SI were characterized functionally and tested for motor output effects on muscle activity. The incidence, character, and magnitude of motor output effects from SI areas were in sharp contrast to effects from CM cell sites in primary motor cortex. Of 68 SI cells tested with spike-triggered averaging, only one area 3a cell produced significant PSpF in spike-triggered averages of EMG activity. In comparison, 20 of 171 (12%) motor cortex cells tested produced significant postspike effects. Single-pulse intracortical microstimulation produced effects at all CM cell sites in motor cortex but at only 14% of SI sites. The large fraction of SI effects that was inhibitory represented yet another marked difference between CM cell sites in motor cortex and SI sites (25% vs 93%). The fact that motor output effects from SI were frequently absent or very weak and predominantly inhibitory emphasizes the differing motor capabilities of SI compared with primary motor cortex.
Serotonin Modulates Voltage-Dependent Calcium Current inNecturusTaste Cells
Authors: Delay Rona J. , Kinnamon Sue C. , Roper Stephen D.
Published: December 2017

Delay, Rona J., Sue C. Kinnamon, and Stephen D. Roper. Serotonin modulates voltage-dependent calcium current in Necturus taste cells. J. Neurophysiol. 77: 2515–2524, 1997. Necturus taste buds contain two primary cell types: taste receptor cells and basal cells. Merkel-like basal cells are a subset of basal cells that form chemical synapses with taste receptor cells and with innervating nerve fibers. Although Merkel-like basal cells cannot interact directly with taste stimuli, recent studies have shown that Merkel-like basal cells contain serotonin (5-HT), which may be released onto taste receptor cells in response to taste stimulation. With the use of whole cell voltage clamp, we examined whether focal applications of 5-HT to isolated taste receptor cells affected voltage-activated calcium current ( ICa). Two different effects were observed. 5-HT at 100 μM increased ICain 33% of taste receptor cells, whereas it decreased ICain 67%. Both responses used a 5-HT receptor subtype with a pharmacological profile similar to that of the 5-HT1Areceptor, but the potentiation and inhibition of ICaby 5-HT were mediated by two different second-messenger cascades. The results indicate that functional subtypes of taste receptor cells, earlier defined only by their sensitivity to taste stimuli, may also be defined by their response to the neurotransmitter 5-HT and suggest that 5-HT released by Merkel-like basal cells could modulate taste receptor function.
NMDA Receptors Contribute to Primary Visceral Afferent Transmission in the Nucleus of the Solitary Tract
Authors: Aylwin Maria Luz , Horowitz John M. , Bonham Ann C.
Published: December 2017

Aylwin, Maria Luz, John M. Horowitz, and Ann C. Bonham. NMDA receptors contribute to primary visceral afferent transmission in the nucleus of the solitary tract. J. Neurophysiol. 77: 2539–2548, 1997. The nucleus of the solitary tract (NTS) is a principal site for coordinating the reflex control of autonomic function. The nucleus receives and organizes primary visceral (sensory) afferent inputs from the great vessels, heart, lung, and gastrointestinal organs. Glutamate, the excitatory neurotransmitter released by the primary afferent fibers, activates non- N-methyl-d-aspartate (non-NMDA) receptors on second-order neurons in the NTS. Still in question is whether NMDA receptors on the second-order neurons are also activated. Accordingly, the purpose of this study was to directly determine whether NMDA receptors contribute to synaptic transmission of primary visceral afferent input to second-order neurons in the NTS. Whole cell patch-clamp recordings were obtained from intermediate and caudal NTS neurons in rat coronal medullary slices. Excitatory postsynaptic currents (EPSCs) were evoked by stimulation of the solitary tract (1–25 V, 0.1 ms, 0.2 or 0.5 Hz) at membrane potentials ranging from −90 to +60 mV. In 28 of 32 neurons in which current-voltage relationships were obtained for solitary-tract-evoked EPSCs, the currents had short onset latencies (3.42 ± 1.03 ms, mean ± SD), indicating that they were the result of monosynaptic activation of second-order neurons. Solitary-tract-evoked EPSCs had both a fast and a slow component. The amplitude of the slow component was nonlinearly related to voltage (being revealed only at membrane potentials positive to −45 mV), blocked by the NMDA receptor antagonist dl-2-amino-5-monophosphovaleric acid (APV, 50 μM; n = 12; P = 0.0001), and enhanced in nominally Mg2+-free perfusate at membrane potentials negative to −45 mV ( n = 5; P = 0.016), demonstrating that the slow component was mediated by NMDA receptors. The amplitude of the fast component was linearly related to voltage and blocked by the non-NMDA receptor antagonist 2,3-dihydroxy-6-nitro-7-sulfamoylbenzo(F)quinoxaline (NBQX, 3 μM; n = 9; P = 0.0014), demonstrating that the fast component was mediated by non-NMDA receptors. The slow component of the EPSCs was not blocked by NBQX ( n = 6; P = 0.134), nor was the fast component blocked by APV ( n = 12; P = 0.124). These results show that both NMDA and non-NMDA receptors coexist on the same second-order NTS neurons and mediate primary visceral afferent transmission in the NTS. The participation of NMDA receptors suggests that second-order neurons in the NTS may have previously unrecognized integrative capabilities in the reflex control of autonomic function.