bluuebunny/crossref_metadata_2025 huggingface dataset:
NREM delta stimulation following MK-801 is a response of sleep systems
Authors: Campbell I. G. , Feinberg I.
Published: December 2017

1. We have previously shown that noncompetitive blockade of the N-methyl-D-aspartate (NMDA)-gated cation channel with ketamine or Dizocilpine maleate (MK-801) increases the intensity of non-rapid-eye-movement (NREM) delta during subsequent sleep. This delta increase [measured as integrated amplitude (IA) in 1- to 4-Hz electroencephalogram (EEG)] occurs in the 12-h period following intraperitoneal injection. However, the 12 h after drug injection is also the period in which these drugs induce neurotoxic changes, raising the possibility that the increased delta represents toxic EEG slowing rather than an increase in the physiological delta waves of NREM sleep. 2. We hypothesized that the time course of delta stimulation could be separated from the time course of neurotoxicity. We tested this hypothesis by injecting 0.3 mg/kg MK-801 at the start of the dark period (DP) and depriving rats of sleep until the onset of the light period (LP) 12 h later. 3. There were two control groups: one received MK-801 at the start of the DP with no further manipulation, and the second received a saline injection at DP onset followed by 12 h of sleep deprivation. The dependent variable was the amount of delta IA in the LP, whose onset was 12 h after MK-801 injection. Total IA in the LP was significantly greater in rats that received MK-801 followed by sleep deprivation than in rats that received sleep deprivation alone or MK-801 alone. 4. This finding indicates that delta stimulation by MK-801 is maintained over 12 h of waking, indicating that the delta increase is not due to toxic EEG slowing or persisting MK-801. Instead, NMDA channel blockade by MK-801 increases the homeostatic need for delta or else directly alters sleep regulatory systems. We speculate that these effects are mediated by hypothalamic sleep centers through control of neuroendocrine pulses that produce both NREM and rapid-eye-movement sleep. 5. Imposing a period of waking between drug administration and sleep onset may prove a generally useful strategy for determining whether a drug affects the homeostatic need for sleep or acutely stimulates sleep systems. This strategy can also help distinguish between toxic and physiological increases in delta EEG.
Greater residual vision in monkeys after striate cortex damage in infancy
Authors: Moore T. , Rodman H. R. , Repp A. B. , Gross C. G. , Mezrich R. S.
Published: December 2017

1. Monkeys with large unilateral surgical ablations of striate cortex, sustained either in adulthood or at 5–6 wk of age, were trained on an oculomotor detection and localization task and tested with visual stimuli in the hemifields ipsilateral and contralateral to the lesion 2–5 yr after surgery. 2. Monkeys with lesions sustained in adulthood were largely unable to detect stimuli in the hemifield contralateral to the lesion, with only one monkey showing recovery toward the end of testing. Monkeys with lesions of striate cortex made in infancy, however, each showed residual detection capacity at the beginning of testing and improved to near normal by the end of testing. 3. Each of the monkeys showing a residual ability to detect within the contralateral hemifield was also able to localize visual targets with eye movements. 4. These findings demonstrate that the vision surviving striate cortex damage in primates is more robust after early damage as has been shown to be the case for primary somatosensory, motor, and association cortex.
Effects of Adaptation on Neural Coding by Primary Sensory Interneurons in the Cricket Cercal System
Authors: Clague Heather , Theunissen Frédéric , Miller John P.
Published: December 2017

Clague, Heather, Frédéric Theunissen, and John P. Miller. Effects of adaptation on neural coding by primary sensory interneurons in the cricket cercal system. J. Neurophysiol. 77: 207–220, 1997. Methods of stochastic systems analysis were applied to examine the effect of adaptation on frequency encoding by two functionally identical primary interneurons of the cricket cercal system. Stimulus reconstructions were obtained from a linear filtering transformation of spike trains elicited in response to bursts of broadband white noise air current stimuli (5–400 Hz). Each linear reconstruction was compared with the actual stimulus in the frequency domain to obtain a measure of waveform coding accuracy as a function of frequency. The term adaptation in this paper refers to the decrease in firing rate of a cell after the onset or increase in power of a white noise stimulus. The increase in firing rate after stimulus offset or decrease in stimulus power is assumed to be a complementary aspect of the same phenomenon. As the spike rate decreased during the course of adaptation, the total amount of information carried about the velocity waveform of the stimulus also decreased. The quality of coding of frequencies between 70 and 400 Hz decreased dramatically. The quality of coding of frequencies between 5 and 70 Hz decreased only slightly or even increased in some cases. The disproportionate loss of information about the higher frequencies could be attributed in part to the more rapid loss of spikes correlated with high-frequency stimulus components than of spikes correlated with low-frequency components. An increase in the responsiveness of a cell to frequencies >70 Hz was correlated with a decrease in the ability of that cell to encode frequencies in the 5–70 Hz range. This nonlinear property could explain the improvement seen in some cases in the coding accuracy of frequencies between 5 and 70 Hz during the course of adaptation. Waveform coding properties also were characterized for fully adapted neurons at several stimulus intensities. The changes in coding observed through the course of adaptiation were similar in nature to those found across stimulus powers. These changes could be accounted for largely by a change in neural sensitivity. The effect of adaptation on the coding of stimulus power was examined by measuring the response curves to steps in stimulus power before and after exposure to an adapting stimulus. Adaptation caused a loss of information about the mean stimulus power but did not cause any improvement in the coding of changes in stimulus power. The unadapted response of the cells did not show any saturation even at the highest powers used in these experiments.
Primary Afferent Neurons Innervating Guinea Pig Dura
Authors: Bove Geoffrey M. , Moskowitz Michael A.
Published: December 2017

Bove, Geoffrey M. and Michael A. Moskowitz. Primary Afferent Neurons Innervating Guinea Pig Dura. J. Neurophysiol. 77: 299–308, 1997. We made recordings from filaments of guinea pig nasociliary nerve to study response properties of afferent axons innervating the anterior superior sagittal sinus and surrounding dura mater. We analyzed 38 units in 14 experiments. Units were initially located with the use of mechanical stimuli, and were then characterized by their conduction velocity and sensitivities to mechanical, thermal, and chemical stimuli. Single-unit recordings revealed innervation of dura and superior sagittal sinus by slowly conducting axons, mostly in the unmyelinated range. The receptive fields were 1–30 mm2, and typically had one to three punctate spots of highest sensitivity. All units tested responded to topical application of chemical agents. Ninety-seven percent of units responded to 10−5 M capsaicin, 79% responded to a mixture of inflammatory mediators, and 37% responded to an acidic buffer (pH 5). These data underline the importance of chemical sensitivity in intracranial sensation. Heat and cold stimuli evoked responses in 56 and 41% of units tested, respectively. Although the response patterns during heating were typical of polymodal nociceptors innervating other tissues, the thresholds were lower than for other tissues (32.3–42°C). Cooling led to a phasic discharge, with thresholds between 25 and 32°C. Although units had different combinations of responses to mechanical, chemical, and thermal stimuli, when grouped by their sensitivities the groups did not differ regarding mechanical thresholds or presence of ongoing activity. This suggests that meningeal primary afferents are relatively homogeneous. Sensitivities of these units are in general consistent with nociceptors, although the thermal thresholds differ. These data provide the first detailed report of response properties of intracranial primary afferent units, likely to be involved in transmission of nociception and possibly mediation of intracranial pain.
Function of the Hyperpolarization-Activated Inward Rectification in Nonmyelinated Peripheral Rat and Human Axons
Authors: Grafe Peter , Quasthoff Stefan , Grosskreutz Julian , Alzheimer Christian
Published: December 2017

Grafe, Peter, Stefan Quasthoff, Julian Grosskreutz, and Christian Alzheimer. Function of the hyperpolarization-activated inward rectification in nonmyelinated peripheral rat and human axons. J. Neurophysiol. 77: 421–426, 1997. The function of time-dependent, hyperpolarization-activated inward rectification was analyzed on compound potentials of nonmyelinated axons in the mammalian peripheral nervous system. Isolated rat vagus nerves and fascicles of biopsied human sural nerve were tested in a three-chambered, Vaseline-gap organ bath at 37°C. Inward rectification was assessed by recording the effects of long-lasting hyperpolarizing currents on electrical excitability with the use of the method of threshold electrotonus (program QTRAC, copyright Institute of Neurology, London, UK) and by measuring activity-dependent changes in conduction velocity and membrane potential. Prominent time-dependent, cesium-sensitive inward rectification was revealed in rat vagus and human sural nerve by recording threshold electrotonus to 200-ms hyperpolarizing current pulses. A slowing of compound action potential conduction was observed during a gradual increase in the stimulation frequency from 0.1 to 3 Hz. Above a stimulation frequency of 0.3 Hz, this slowing of conduction was enhanced during bath application of 1 mM cesium. Cesium did not alter action potential waveforms during stimulation at frequencies <1 Hz. Cesium-induced slowing in action potential conduction was correlated with membrane hyperpolarization. The hyperpolarization by cesium was stronger during higher stimulation frequencies and small in unstimulated nerves. These data show that a cesium-sensitive, time-dependent inward rectification in peripheral rat and human nonmyelinated nerve fibers limits the slowing in conduction seen in such axons at action potential frequencies higher than ∼0.3 Hz.
Low-Threshold Mechanoreceptive Afferents in the Human Lingual Nerve
Authors: Trulsson Mats , Essick Gregory K.
Published: December 2017

Trulsson, Mats and Gregory K. Essick. Low-threshold mechanoreceptive afferents in the human lingual nerve. J. Neurophysiol. 77: 737–748, 1997. Intrafascicular multiunit activity and impulses in single mechanoreceptive afferents were recorded from the human lingual nerve with permucosally inserted tungsten microelectrodes. Nylon filaments and blunt glass probes were used for mechanical stimulation of the mucosa of the dorsal surface of the tongue. The innervation territories of nine nerve fascicles were mapped during multiunit recordings. All fascicle fields included the tip of the tongue, suggesting a particularly high innervation density for this area. Thirty-three single mechanoreceptive afferents were isolated and studied. Of these afferents, 22 were characterized by very small mucosal receptive fields (range: 1–19.6 mm2; geometric mean: 2.4 mm2) and responded to extremely low mechanical forces (force threshold range: 0.03–2 mN; geometric mean: 0.15 mN). As such, it was concluded that these “superficial” units terminated near the surface of the tongue. The remaining 11 units responded to probing of large areas of the tongue (>200 mm2) and exhibited high force thresholds (≥4 mN). It was concluded that these “deep” units terminated in the muscle mass of the tongue. Fourteen of the superficial units were classified as rapidly adapting and resembled the fast-adapting type I afferents described for the glabrous skin of the human hand. The rapidly adapting units responded both during the application and removal of, but not during maintenance of, the mechanical stimuli on the receptive field. Two types of slowly adapting responses were observed. One type (characteristic of only 2 units) was characterized by a pronounced sensitivity to force change during the application and removal of the mechanical stimuli and an irregular static discharge during maintenance of the stimulus on the receptive field. In contrast, the other six units exhibited a weak sensitivity to force change, a highly regular static discharge, and spontaneous activity. As such, these two types of slowly adapting units resembled the slowly adapting I and II afferents, respectively, described for the hand. All 11 deep units were slowly adapting, and 7 were, in addition, spontaneously active. The units were not equally sensitive to the application and removal of the mechanical stimuli, suggesting at least two different modes of termination in tongue muscle. The deep units reliably encoded information about tongue movements in the absence of direct contact with the receptive field. In contrast, the superficial units responded vigorously when the tongue was moved to bring the receptive field into physical contact with other intraoral structures.
Coincident Stimulation With Pheromone Components Improves Temporal Pattern Resolution in Central Olfactory Neurons
Authors: Christensen Thomas A. , Hildebrand John G.
Published: December 2017

Christensen, Thomas A. and John G. Hildebrand. Coincident stimulation with pheromone components improves temporal pattern resolution in central olfactory neurons. J. Neurophysiol. 77: 775–781, 1997. Male moths must detect and resolve temporal discontinuities in the sex pheromonal odor signal emitted by a conspecific female moth to orient to and locate the odor source. We asked how sensory information about two key components of the pheromone influences the ability of certain sexually dimorphic projection (output) neurons in the primary olfactory center of the male moth's brain to encode the frequency and duration of discrete pulses of pheromone blends. Most of the male-specific projection neurons examined gave mixed postsynaptic responses, consisting of an early suppressive phase followed by activation of firing, to stimulation of the ipsilateral antenna with a blend of the two behaviorally essential pheromone components. Of 39 neurons tested, 33 were excited by the principal (most abundant) pheromone component but inhibited by another, less abundant but nevertheless essential component of the blend. We tested the ability of each neuron to encode intermittent pheromonal stimuli by delivering trains of 50-ms pulses of the two-component blend at progressively higher rates from 1 to 10 per second. There was a strong correlation between 1) the amplitude of the early inhibitory postsynaptic potential evoked by the second pheromone component and 2) the maximal rate of odor pulses that neuron could resolve ( r = 0.92). Projection neurons receiving stronger inhibitory input encoded the temporal pattern of the stimulus with higher fidelity. With the principal, excitatory component of the pheromone alone as the stimulus, the dynamic range for encoding stimulus intermittency was reduced in nearly 60% of the neurons tested. The greatest reductions were observed in those neurons that could be shown to receive the strongest inhibitory input from the second behaviorally essential component of the blend. We also tested the ability of these neurons to encode stimulus duration. Again there was a strong correlation between the strength of the inhibitory input to a neuron mediated by the second pheromone component and that neuron's ability to encode stimulus duration. Neurons that were strongly inhibited by the second component could accurately encode pulses of the blend from 50 to 500 ms in duration ( r = 0.94), but that ability was reduced in neurons receiving little or no inhibitory input ( r = 0.23). This study confirms that certain olfactory projection neurons respond optimally to a particular odor blend rather than to the individual components of the blend. The key components activate opposing synaptic inputs that enable this subset of central neurons to copy the duration and frequency of intermittent odor pulses that are a fundamental feature of airborne olfactory stimuli.
Reaching Movements With Similar Hand Paths But Different Arm Orientations. I. Activity of Individual Cells in Motor Cortex
Authors: Scott Stephen H. , Kalaska John F.
Published: December 2017

Scott, Stephen H. and John F. Kalaska. Reaching movements with similar hand paths but different arm orientations. I. Activity of individual cells in motor cortex. J. Neurophysiol. 77: 826–852, 1997. This study shows that the discharge of many motor cortical cells is strongly influenced by attributes of movement related to the geometry and mechanics of the arm and not only by spatial attributes of the hand trajectory. The activity of 619 directionally tuned cells was recorded from the motor cortex of two monkeys during reaching movements with the use of similar hand paths but two different arm orientations, in the natural parasagittal plane and abducted into the horizontal plane. Nearly all cells (588 of 619, 95%) showed statistically significant changes in activity between the two arm orientations [analysis of variance (ANOVA), P < 0.01]. A majority of cells showed a significant change in their overall level of activity (ANOVA, main effect of task, P < 0.01) between arm orientations before, during, and after movement. Many cells (433 of 619, 70%) also showed a significant change in the relation of their discharge with movement direction(ANOVA, task × direction interaction term, P < 0.01) during movement, including changes in the dynamic range of discharge with movement and changes in the directional preference of cells that were directionally tuned in both arm orientations. Similar effects were seen for the discharge of cells while the monkey maintained constant arm postures over the different peripheral targets with the use of different arm orientations. Repeated data files from the same cell with the use of the same arm orientation showed only small changes in the level of discharge or in directional tuning, suggesting that changes in cell discharge between arm orientations cannot be explained by random temporal variations in cell activity. The distribution of movement-related preferred directions of the whole sample differed between arm orientations, and also differed strongly between cells receiving passive input predominantly from the shoulder or elbow. The electromyographic activity of most prime mover muscles at the shoulder and elbow was also strongly affected by arm orientation, resulting in changes in overall level of activity and/or directional tuning that often resembled those of the proximal arm-related motor cortical cells. A mathematical model that represented movements in terms of movement direction centered on the hand could not account for any of the arm-orientation-related response changes seen in this task, whereas models in intrinsic parameter spaces of joint kinematics and joint torques predicted many of the effects.
Infrequent Events Transiently Activate Human Prefrontal and Parietal Cortex as Measured by Functional MRI
Authors: McCarthy Gregory , Luby Marie , Gore John , Goldman-Rakic Patricia
Published: December 2017

McCarthy, Gregory, Marie Luby, John Gore, and Patricia Goldman-Rakic. Infrequent events transiently activate human prefrontal and parietal cortex as measured by functional MRI. J. Neurophysiol. 77: 1630–1634, 1997. P300 is an event-related potential elicited by infrequent target events whose amplitude is dependent on the context provided by the immediately preceding sequence of stimuli, suggesting its dependence on working memory. We employed magnetic resonance imaging sequences sensitive to blood oxygenation level to identify regional changes evoked by infrequent visual target stimuli presented in a task typically used to elicit P300. Targets evoked transient event-related activation bilaterally in the middle frontal gyrus, in the inferior parietal lobe, and near the inferior aspect of the posterior cingulate gyrus beginning within 1.5 s of target onset and peaking between 4.5 and 6 s. These regions have been identified in previous neuroimaging studies in humans, and in single-unit recordings in monkeys, as components of a neural system mediating working memory, which suggests that this system may be activated by the same events that evoke P300.
Functional Properties of Neurons in Macaque Area V3
Authors: Gegenfurtner Karl R. , Kiper Daniel C. , Levitt Jonathan B.
Published: December 2017

Gegenfurtner, Karl R., Daniel C. Kiper, and Jonathan B. Levitt. Functional properties of neurons in macaque area V3. J. Neurophysiol. 77: 1906–1923, 1997. We investigated the functional properties of neurons in extrastriate area V3. V3 receives inputs from both magno- and parvocellular pathways and has prominent projections to both the middle temporal area (area MT) and V4. It may therefore represent an important site for integration and transformation of visual signals. We recorded the activity of single units representing the central 10° in anesthetized, paralyzed macaque monkeys. We measured each cell's spatial, temporal, chromatic, and motion properties with the use of a variety of stimuli. Results were compared with measurements made in V2 neurons at similar eccentricities. Similar to area V2, most of the neurons in our sample (80%) were orientation selective, and the distribution of orientation bandwidths was similar to that found in V2. Neurons in V3 preferred lower spatial and higher temporal frequencies than V2 neurons. Contrast thresholds of V3 neurons were extremely low. Achromatic contrast sensitivity was much higher than in V2, and similar to that found in MT. About 40% of all neurons showed strong directional selectivity. We did not find strongly directional cells in layer 4 of V3, the layer in which the bulk of V1 and V2 inputs terminate. This property seems to be developed within area V3. An analysis of the responses of directionally selective cells to plaid patterns showed that in area V3, as in MT and unlike in V1 and V2, there exist cells sensitive to the motion of the plaid pattern rather than to that of the components. The exact proportion of cells classified as being selective to color depended to a large degree on the experiment and on the criteria used for classification. With the use of the same conditions as in a previous study of V2 cells, we found as many (54%) color-selective cells as in V2 (50%). Furthermore, the responses of V3 cells to colored sinusoidal gratings were well described by a linear combination of cone inputs. The two subpopulations of cells responsive to color and to motion overlapped to a large extent, and we found a significant proportion of cells that gave reliable and directional responses to drifting isoluminant gratings. Our results show that there is a significant interaction between color and motion processing in area V3, and that V3 cells exhibit the more complex motion properties typically observed at later stages of visual processing.
Form Processing Modules in Primate Area V4
Authors: Ghose Geoffrey M. , Ts'O Daniel Y.
Published: December 2017

Ghose, Geoffrey M. and Daniel Y. Ts'o. Form processing modules in primate area V4. J. Neurophysiol. 77: 2191–2196, 1997. Area V4 occupies a central position among the areas of the primate cerebral cortex involved with object recognition and analysis. Consistent with this role, neurons in V4 are selective for many visual attributes including color, orientation, and binocular disparity. However, it is uncertain whether cells within V4 are organized with respect to these properties. In this study we used in vivo optical imaging and electrophysiology in macaque visual cortex to show that cells that share certain physiological properties are indeed grouped together in V4. Our results revealed regions containing cells with common orientation selectivity. These regions were similar in size to those seen in V2 and much larger than those seen in V1 and were confirmed by appropriately targeted single-unit recording. Surprisingly, orientation organization visible through imaging was limited to the portion of V4 representing the central visual fields. Optical imaging also revealed a functional organization related to stimulus size. Size-sensitive regions (S regions) contained cells that were strongly suppressed by large stimuli. In contrast to V2, S regions in V4 contain orientation domains. These results suggest that V4 contains modular assemblies of cells related to particular aspects of form analysis. Such organization may contribute to the construction of object-based representations.
Neural Tuning to Sound Duration in the Inferior Colliculus of the Big Brown Bat, Eptesicus fuscus
Authors: Ehrlich Daphna , Casseday John H. , Covey Ellen
Published: December 2017

Ehrlich, Daphna, John H. Casseday, and Ellen Covey. Neural tuning to sound duration in the inferior colliculus of the big brown bat, Eptesicus fuscus. J. Neurophysiol. 77: 2360–2372, 1997. Neural tuning to different sound durations may be a useful filter for identification of certain sounds, especially those that are biologically important. The auditory midbrains of mammals and amphibians contain neurons that appear to be tuned to sound duration. In amphibians, neurons are tuned to durations of sound that are biologically important. The purpose of this study was to characterize responses of neurons in the inferior colliculus (IC) of the big brown bat, Eptesicus fuscus, to sounds of different durations. Our aims were to determine what percent of neurons are duration tuned and how best durations are correlated to durations of echolocation calls, and to examine response properties that may be relevant to the mechanism for duration tuning, such as latency and temporal firing pattern; we also examined frequency tuning and rate-level functions. We recorded from 136 single units in the central nucleus of the IC of unanesthetized bats. The stimuli were pure tones, frequency-modulated sweeps, and broadband noise. The criterion for duration tuning was an increase in spike count of ≥50% at some durations compared with others. Of the total units sampled, 36% were tuned to stimulus duration. All of these units were located in the caudal half of the IC. Best duration for most units ranged from <1 to 10 ms, but a few had best durations up to ≥20 ms. This range is similar to the range of durations of echolocation calls used by Eptesicus. All duration-tuned neurons responded transiently. The minimum latency was always longer than the best duration. Duration-tuned units have best durations and best frequencies that match the temporal structure and frequency range of the echolocation calls. Thus the results raise the hypothesis that neurons in the IC of Eptesicus, and probably the auditory midbrain of other vertebrates, are tuned to biologically important sound durations. We suggest a model for duration tuning consisting of three components: 1) inhibitory input that is correlated with the onset of the stimulus and is sustained for the stimulus duration; 2) transient excitation that is correlated with the offset of the stimulus; and 3) transient excitation that is correlated with the onset of the stimulus but is delayed in time relative to the onset of inhibition. For the neuron to fire, the two excitatory events must coincide in time; noncoincident excitatory events are not sufficient.
Bidirectional Associative Plasticity of Unitary CA3-CA1 EPSPs in the Rat Hippocampus In Vitro
Authors: Debanne Dominique , Gähwiler Beat H. , Thompson Scott M.
Published: December 2017

Debanne, Dominique, Beat H. Gähwiler, and Scott M. Thompson. Bidirectional associative plasticity of unitary CA3-CA1 EPSPs in the rat hippocampus in vitro. J. Neurophysiol. 77: 2851–2855, 1997. Associative long-term potentiation (LTP) and depression of compound and unitary CA3-CA1 excitatory postsynaptic potentials (EPSPs) were investigated in rat hippocampal slice cultures. The induction of LTP with synchronous pairing of synaptic activation and postsynaptic depolarization resulted in an increase in the amplitude of EPSPs to the same absolute level, regardless of whether the input was naive or had been previously depressed by asynchronous pairing of pre- and postsynaptic activity. Saturated LTP of compound and unitary EPSPs was reversed by asynchronous pairing and could be reinduced by synchronous pairing. The likelihood that an action potential in a presynaptic CA3 cell failed to trigger an unitary EPSP in a postsynaptic CA1 cell decreased after induction of associative potentiation and increased after induction of associative depotentiation. These changes in the rate of transmission failures were accompanied by large changes in the amplitude of nonfailure EPSPs. We conclude that the same CA3-CA1 synapses can alternatively undergo associative potentiation and depression, perhaps through opposite changes in a single expression mechanism.
Recordings From Brain Stem Neurons Responding to Chemical Stimulation of the Subarachnoid Space
Authors: Ebersberger A. , Ringkamp M. , Reeh P. W. , Handwerker H. O.
Published: December 2017

Ebersberger, A., M. Ringkamp, P. W. Reeh, and H. O. Handwerker. Recordings from brain stem neurons responding to chemical stimulation of the subarachnoid space. J. Neurophysiol. 77: 3122–3133, 1997. The subarachnoid space at the base of the skull was perfused continuously with artificial cerebrospinal fluid in anesthetized rats. A combination of inflammatory mediators consisting of histamine, bradykinin, serotonin, and prostaglandin E2 (10−5 M) at pH of 6.1 was introduced into the flow for defined periods to stimulate meningeal primary afferents. Secondary neurons in the caudal nucleus of the trigeminal brain stem were searched by electrical stimulation of the cornea. Of the units receiving oligosynaptic input from the cornea, 44% were excited by stimulation of the meninges with inflammatory mediators. Most of these units had small receptive fields including cornea and the periorbital region, and their responsiveness was restricted to stimuli of noxiuos intensity. Three types of responses to stimulation of the meninges with algogenic agents were encountered: responses that did not outlast the stimulus period, responses outlasting the stimulus period for several minutes, and oscillating response patterns containing periods of enhanced and suppressed activity. The response pattern of a unit was reproducible, however, upon repetitive stimulation at 20-min intervals; the response magnitude showed tachyphylaxis upon stimulus repetition. The preparation presented mimics pathophysiolocial states normally accompanied by headache, e.g., subarachnoidal bleeding. Responsiveness of neurons in the caudal nucleus of the trigeminal brain stem to inflammatory mediators may play a role in the generation and maintenance of headache, e.g., migraine.
Synchronized Oscillations in the Inferior Olive Are Controlled by the Hyperpolarization-Activated Cation Current I h
Authors: Bal Thierry , McCormick David A.
Published: December 2017

Bal, Thierry and David A. McCormick. Synchronized oscillations in the inferior olive are controlled by the hyperpolarization-activated cation current I h. J. Neurophysiol. 77: 3145–3156, 1997. The participation of a hyperpolarization-activated cationic current in the generation of oscillations in single inferior olive neurons and in the generation of ensemble oscillations in the inferior olive nucleus (IO) of the guinea pig and ferret was investigated in slices maintained in vitro. Intracellular recordings in guinea pig or ferret IO neurons revealed that these cells could generate sustained endogenous oscillations (4–10 Hz) at hyperpolarized membrane potentials (−60 to −67 mV) after the intracellular injection of a brief hyperpolarizing current pulse. These oscillations appeared as the rhythmic generation of a low-threshold Ca2+ spike that typically initiated one or two fast Na+-dependent action potentials. Between low-threshold Ca2+ spikes was an afterhyperpolarization that formed a “pacemaker” potential. Local application of apamin resulted in a large reduction in the amplitude of the afterhyperpolarization, indicating that a Ca2+-activated K+ current makes a strong contribution to its generation. However, even in the presence of apamin, hyperpolarization of IO neurons results in a “depolarizing sag” of the membrane potential that was blocked by local application of Cs+ or partial replacement of extracellular Na+ with choline+ or N-methyl-d-glucamine+, suggesting that I h also contributes to the generation of the afterhyperpolarization. Extracellular application of low concentrations of cesium resulted in hyperpolarization of the membrane potential of IO neurons and spontaneous 5- to 6-Hz oscillations in single, as well as networks, of IO neurons. Application of larger concentrations of cesium reduced the frequency of oscillation to 2–3 Hz or blocked the oscillation entirely. On the basis of these results, we propose that I h contributes to single and ensemble oscillations in the IO in two ways: 1) I h contributes to the determination of the resting membrane potential such that reduction of I h results in hyperpolarization of the membrane potential and an increased propensity of oscillation through removal of inactivation of the low-threshold Ca2+ current; and 2) I h contributes to the generation of the afterhyperpolarization and the pacemaker potential between low-threshold Ca2+ spikes.
Synaptic Physiology and Mitochondrial Function in Crayfish Tonic and Phasic Motor Neurons
Authors: Nguyen Peter V. , Marin Leo , Atwood Harold L.
Published: December 2017

Nguyen, Peter V., Leo Marin, and Harold L. Atwood. Synaptic physiology and mitochondrial function in crayfish tonic and phasic motor neurons. J. Neurophysiol. 78: 281–294, 1997. Phasic and tonic motor neurons of crustaceans differ strikingly in their junctional synaptic physiology. Tonic neurons generally produce small excitatory postsynaptic potentials (EPSPs) that facilitate strongly as stimulation frequency is increased, and normally show no synaptic depression. In contrast, phasic neurons produce relatively large EPSPs with weak frequency facilitation and pronounced depression. We addressed the hypothesis that mitochondrial function is an important determinant of the features of synaptic transmission in these neurons. Mitochondrial fluorescence was measured with confocal microscopy in phasic and tonic axons and terminals of abdominal and leg muscles after exposure to supravital mitochondrial fluorochromes, rhodamine-123 (Rh123) and 4-diethylaminostyryl-N-methylpyridinium iodide (4-Di-2-Asp). Mitochondria of tonic axons and neuromuscular junctions had significantly higher mean Rh123 and 4-Di-2-Asp fluorescence than in phasic neurons, indicating more accumulation of the fluorochromes. Mitochondrial membrane potential, which is responsible for Rh123 uptake and is related to mitochondrial oxidative activity (the production of ATP by oxidation of metabolic substrates), is likely higher in tonic axons. Electron microscopy showed that tonic axons contain approximately fivefold more mitochondria per μm2cross-sectional area than phasic axons. Neuromuscular junctions of tonic axons also have a much higher mitochondrial content than those of phasic axons. We tested the hypothesis that synaptic fatigue resistance is dependent on mitochondrial function in crayfish motor axons. Impairment of mitochondrial function by uncouplers of oxidative phosphorylation, dinitrophenol or carbonyl cyanide m-chlorophenylhydrazone, or by the electron transport inhibitor sodium azide, led to marked synaptic depression of a tonic axon and accelerated depression of a phasic axon during maintained stimulation. Iodoacetate, an inhibitor of glycolysis, and chloramphenicol, a mitochondrial protein synthesis inhibitor, had no significant effects on either mitochondrial fluorescence or synaptic depression in tonic or phasic axons. Collectively, the results provide evidence that mitochondrial oxidative metabolism is important for sustaining synaptic transmission during maintained stimulation of tonic and phasic motor neurons. Tonic neurons have a higher mitochondrial content and greater oxidative activity; these features are correlated with their greater resistance to synaptic depression. Conversely, phasic neurons have a lower mitochondrial content, less oxidative activity, and greater synaptic fatigability.
Intracellular and Computational Characterization of the Intracortical Inhibitory Control of Synchronized Thalamic Inputs In Vivo
Authors: Contreras Diego , Destexhe Alain , Steriade Mircea
Published: December 2017

Contreras, Diego, Alain Destexhe, and Mircea Steriade. Intracellular and computational characterization of the intracortical inhibitory control of synchronized thalamic inputs in vivo. J. Neurophysiol. 78: 335–350, 1997. We investigated the presence and role of local inhibitory cortical control over synchronized thalamic inputs during spindle oscillations (7–14 Hz) by combining intracellular recordings of pyramidal cells in barbiturate-anesthetized cats and computational models. The recordings showed that 1) similar excitatory postsynaptic potential (EPSP)/inhibitory postsynaptic potential (IPSP) sequences occurred either during spindles or following thalamic stimulation; 2) reversed IPSPs with chloride-filled pipettes transformed spindle-related EPSP/IPSP sequences into robust bursts with spike inactivation, resembling paroxysmal depolarizing shifts during seizures; and 3) dual simultaneous impalements showed that inhibition associated with synchronized thalamic inputs is local. Computational models were based on reconstructed pyramidal cells constrained by recordings from the same cells. These models showed that the transformation of EPSP/IPSP sequences into fully developed spike bursts critically needs a relatively high density of inhibitory currents in the soma and proximal dendrites. In addition, models predict significant Ca2+transients in dendrites due to synchronized thalamic inputs. We conclude that synchronized thalamic inputs are subject to strong inhibitory control within the cortex and propose that 1) local impairment of inhibition contributes to the transformation of spindles into spike-wave-type discharges, and 2) spindle-related inputs trigger Ca2+events in cortical dendrites that may subserve plasticity phenomena during sleep.
The Motor System Does Not Learn the Dynamics of the Arm by Rote Memorization of Past Experience
Authors: Conditt Michael A. , Gandolfo Francesca , Mussa-Ivaldi Ferdinando A.
Published: December 2017

Conditt, Michael A., Francesca Gandolfo, and Ferdinando A. Mussa-Ivaldi. The motor system does not learn the dynamics of the arm by rote memorization of past experience. J. Neurophysiol. 78: 554–560, 1997. The purpose of this study was to investigate the learning mechanisms underlying motor adaptation of arm movements to externally applied perturbing forces. We considered two alternative hypotheses. According to one, adaptation occurs through the learning of a mapping between the states (positions and velocities) visited by the arm and the forces experienced at those states. The alternative hypothesis is that adaptation occurs through the memorization of the temporal sequence of forces experienced along specific trajectories. The first mechanism corresponds to developing a model of the dynamics of the environment, whereas the second is a form of “rote learning.” Both types of learning would lead to the recovery of the unperturbed performance. We have tested these hypotheses by examining how adaptation is transferred across different types of movements. Our results indicate that 1) adaptation to an externally applied force field occurs with different classes of movements including but not limited to reaching movements and 2) adaptation generalizes across different movements that visit the same regions of the external field. These findings are not compatible with the hypothesis of rote learning. Instead, they are consistent with the hypothesis that adaptation to changes in movement dynamics is achieved by a module that learns to reproduce the structure of the environmental field as an association between visited states and experienced forces, independent of the kinematics of the movements made during adaptation.
Neuronal Activity in the Ventral Part of Premotor Cortex During Target-Reach Movement is Modulated by Direction of Gaze
Authors: Mushiake Hajime , Tanatsugu Yasuyuki , Tanji Jun
Published: December 2017

Mushiake, Hajime, Yasuyuki Tanatsugu, and Jun Tanji. Neuronal activity in the ventral part of premotor cortex during target-reach movement is modulated by direction of gaze. J. Neurophysiol. 78: 567–571, 1997. We recorded 200 neurons from the ventral part of the premotor cortex (PMv) and 110 neurons from the primary motor cortex (MI) of a monkey performing a visually cued arm-reaching task with a delay. We compared neuronal activity in the premovement period while the monkey reached the target with the eyes fixating on either a left or right fixation target. Our data demonstrate that about half of the movement-related activity in the PMv was modulated by the direction of gaze. In contrast, a vast majority of the activity of MI neurons and about half of PMv neurons were not influenced by the direction of gaze. We further analyzed the movement-related activity during the reaching movement to targets at the top, bottom, left, and right of each fixation point. The magnitude of activity of neurons showing the gaze-direction selectivity was primarily determined by the position of the reaching target relative to the eye-fixation target, and not by the position of the target relative to the animal's body. These data suggest that a part of the coordinate transformation of the motor command signals concerning the direction of reaching from the retinotopic to body-centered frame of reference may occur at the level of premotor cortex but not in MI.
Residual Binocular Interactions in the Striate Cortex of Monkeys Reared With Abnormal Binocular Vision
Authors: Smith Earl L. , Chino Yuzo M. , Ni Jinren , Cheng Han , Crawford M.L.J. , Harwerth Ronald S.
Published: December 2017

Smith, Earl L., III, Yuzo M. Chino, Jinren Ni, Han Cheng, M.L.J. Crawford, and Ronald S. Harwerth. Residual binocular interactions in the striate cortex of monkeys reared with abnormal binocular vision. J. Neurophysiol. 78: 1353–1362, 1997. We investigated the nature of residual binocular interactions in the striate cortex (V1) of monkey models for the two most common causes of visual dysfunction in young children, specifically anisometropia and strabismus. Infant rhesus monkeys were raised wearing either anisometropic spectacle lenses that optically defocused one eye or ophthalmic prisms that optically produced diplopia and binocular confusion. Earlier psychophysical investigations had demonstrated that all subjects exhibited permanent binocular vision deficits and, in some cases, amblyopia. When the monkeys were adults, the responses of individual V1 neurons were studied with the use of microelectrode recording techniques while the animals were anesthetized and paralyzed. The manner in which the signals from the two eyes were combined in individual cells was investigated by dichoptically stimulating both eyes simultaneously with drifting sine wave gratings. In both lens- and prism-reared monkeys, fewer neurons had balanced ocular dominances and greater numbers of neurons were excited by only one eye. However, many neurons that appeared to be monocular exhibited clear binocular interactions during dichoptic stimulation. For the surviving binocular neurons, the maximum binocular response amplitudes were lower than normal; fewer neurons, particularly complex cells, were sensitive to relative interocular spatial phase disparities; and the remaining disparity-sensitive neurons exhibited lower degrees of binocular interaction. In prism-reared monkeys, an unusually high proportion of complex cells exhibited binocular suppression during dichoptic stimulation. Binocular contrast summation experiments showed that for both cooperative and antagonistic binocular interactions, contrast signals from the two eyes were combined by individual neurons in a normal linear fashion in both lens- and prism-reared monkeys. The observed binocular deficits appear to reflect a reduction in functional inputs from one eye and/or spatial imprecision in the monocular receptive fields rather than an aberrant form of binocular interaction. In the prism-reared monkeys, the predominance of suppression suggests that inhibitory connections were, however, less susceptible to diplopia and confusion than excitatory connections. Overall, there were many parallels between V1 physiology in our monkey models and the residual vision of humans with anisometropia or strabismus.
Regulation of Muscle Stiffness During Periodic Length Changes in the Isolated Abdomen of the Hermit Crab
Authors: Chapple William D.
Published: December 2017

Chapple, William. Regulation of muscle stiffness during periodic length changes in the isolated abdomen of the hermit crab. J. Neurophysiol. 78: 1491–1503, 1997. Reflex activation of the ventral superficial muscles (VSM) in the abdomen of the hermit crab, Pagurus pollicarus, was studied using sinusoidal and stochastic longitudinal vibration of the muscle while recording the length and force of the muscle and the spike times of three exciter motoneurons. In the absence of vibration, the interspike interval histograms of the two larger motoneurons were bimodal; cutting sensory nerves containing most of the mechanoreceptor input removed the short interval peak in the histogram, indicating that the receptors are important in maintaining tonic firing. Vibration of the muscle evoked a reflex increase in motoneuron frequency that habituated after an initial peak but remained above control levels for the duration of stimulation. Motoneuron frequency increased with root mean square (rms) stimulus amplitude. Average stiffness during stimulation was about two times the stiffness of passive muscle. The reflex did not alter muscle dynamics. Estimated transfer functions were calculated from the fast Fourier transform of length and force signals. Coherence was >0.9 for the frequency range of 3–35 Hz. Stiffness magnitude gradually increased over this range in both reflex activated and passive muscle; phase was between 10 and 20°. Reflex stiffness decreased with increasing stimulus amplitudes, but at larger amplitudes, this decrease was much less pronounced; in this range stiffness was regulated by the reflex. The sinusoidal frequency at which reflex bursts were elicited was ∼6 Hz, consistent with previous measurements using ramp stretch. During reflex excitation, there was an increase in amplitude of the short interval peak in the interspike interval histogram; this was reduced when the majority of afferent pathways was removed. A phase histogram of motoneuron firing during sinusoidal vibration had a peak at ∼110 ms, also suggesting that an important component of the reflex is via direct projections from the mechanoreceptors. These results are consistent with the hypothesis that a robust feedforward regulation of abdominal stiffness during continuous disturbances is achieved by mechanoreceptors signalling the absolute value of changing forces; habituation of the reflex, its high-threshold for low frequency disturbances and the activation kinetics of the muscle further modify reflex dynamics.