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J K Chapin

Publications and source records attributed to J K Chapin.

At least 55 records · Page 3Linked to original sources
PubMed1990

A region in the dorsolateral striatum of the rat exhibiting single-unit correlations with specific locomotor limb movements.

1. To examine the activity of single units in the lateral striatum of the awake rat with respect to sensorimotor function, 788 units were recorded during locomotion and passive testing. The focus of this report is on 138 units (18%) that fired in relation to sensorimotor activity of a single limb. The remaining units were related to other body parts (16%), to general body movement (38%), or were unresponsive (28%). 2. Firing rates of limb-related units were near zero during resting behavior but increased markedly during treadmill locomotion. Each of the 138 units exhibited a rhythmic pattern of discharge in phase with the locomotor step cycle. Passive testing revealed that 86/97 units tested (89%) responded to passive manipulation of a single limb, exhibiting increased firing rates. Of these, 77 (90%) were related to contralateral and 9 (10%) to ipsilateral limbs. Sixty-one units (71%) were related to a forelimb and 25 (29%) to a hindlimb. Of the 86 units responding to passive manipulation. 34/48 units tested (71%) also responded to cutaneous stimulation of the same limb but no other part of the body. 3. To study in greater detail the rhythmic unit discharges in phase with the locomotor step cycle, computer-synchronized videotape recordings were used to generate perimovement time histograms constructed around discrete locomotor movements of each limb (n = 17 units). Activity of each unit was shown to be restricted to a specific portion of a particular limb's step cycle. The majority of units discharged throughout (8 units) or during a portion of (3 units) the swing phase, whereas other units fired during a portion of stance (3 units), footfall (2 units), or foot off (1 unit). 1. The specificity of unit firing was further demonstrated by the finding that rhythmic discharges, related to discrete locomotor limb movements in the forward direction, were completely absent during spontaneous deviations such as backward or disrupted locomotion. 5. Units related to limb movement were located in the far lateral, especially the dorsolateral, subregion of the striatum. This subregion extend rostrocaudally from A-P +1.6 to -1.0 mm relative to bregma. No clear somatotopic organization was observed, but this issue requires further study. 6. These results show that functional representations of individual limbs can be demonstrated in the lateral striatum of the rat, within a subregion containing terminals of projections from somatic sensorimotor cortex.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1990

Ketamine effects on somatosensory cortical single neurons and on behavior in rats.

The neurophysiological effects of ketamine were studied at the single-neuron level in the somatosensory cortex of unanesthetized rats behaving in a treadmill movement paradigm. Chronically implanted 25-microns microwire electrodes were used to record spontaneous discharge, sensory responses, and sensorimotor-correlated activity of single neurons before and after ketamine administration. Extracellular action potentials of up to six single neurons were simultaneously recorded for several days, allowing ketamine effects to be tested repeatedly on the same neurons. Videotaped recordings obtained during each experiment were used to measure both the sensorimotor properties of the neurons and the changes in these measures caused by different doses of ketamine. Behaviorally, ketamine produced restless-hyperactive behavior at subanesthetic doses from 5 to 20 mg/kg (intramuscularly). At higher doses (30-50 mg/kg) the rats became cataleptic and immobile after the initial hyperactive period. Whereas the spontaneous rates of most neurons were reduced or unchanged after subanesthetic doses, a subgroup (27% of the total) exhibited markedly increased firing rates. This excitation was of a tonic nature, persisting for a dose-dependent duration in a manner that was not correlated with any of the behavioral effects of the drug. In further analyses, ketamine suppressed the sensory responses of virtually all of the recorded neurons. In particular, low doses of ketamine suppressed "sensorimotor" firing (mainly proprioceptive responses) of neurons in relation to active limb movement. It also suppressed virtually all neuronal sensory responses to the sudden onset of treadmill movement, although the time-course of this effect varied from neuron to neuron. These results reveal two separable effects of ketamine: (a) a strong inhibition of all somatosensory responsiveness in this area and (b) a tonic excitatory influence expressed heterogeneously on a subgroup of neurons. This coexistence of cortical neuronal excitation and sensory suppression in the same cortical region may explain in part the mechanism of dissociative anesthesia and hallucinatory side effects observed in humans during emergence from ketamine anesthesia.

Action Potentials↗
PubMed1990

Mapping the effects of SI cortex stimulation on somatosensory relay neurons in the rat thalamus: direct responses and afferent modulation.

We have used single-unit recording techniques to map the spatial distribution of the primary somatosensory (SI) cortical influences on thalamic somatosensory relay nuclei in the rat. A total of 193 microelectrode penetrations were made to record single neurons in tracks through the medial and lateral ventroposterior (VPL and VPM), ventrolateral (VL), posterior (Po), and reticular (nRt) thalamic nuclei. Single units were classified according to their (1) location within the nuclei, (2) receptive fields, and (3) response to standardized microstimulation in deep layers of the SI cortical forepaw areas. The SI stimulation produced short-latency (1- to 7-msec) excitatory responses in different percentages of neurons recorded in the following thalamic nuclei: VPL, 42.0%; Po, 25.0%; nRt, 16.4%; VL, 13.6%; and VPM, 9.9%. Within the VPL, the highest proportion of responsive neurons was found in the anterior region. Although most of the VL region was unresponsive, the caudal subregion bordering the rostral VPL showed some responsiveness (13.6% of neurons). In general, the spatial pattern of corticothalamic influences appeared to reciprocate the known thalamocortical connection patterns, but with a heterogeneity that was unpredicted. The same parameters of SI cortical stimulation were used in studies of corticofugal modulation of afferent transmission through the VPL thalamus. A condition-test (C-T) paradigm was implemented in which the cortical stimulation (C) was delivered at a range of time intervals before test (T) mechanical vibratory stimulation was applied to digit 4 of the contralateral forepaw. The time course of cortical effects was analyzed by measuring the averaged evoked unit responses of thalamic neurons to the T stimuli, and plotting them as a function of C-T intervals from 5 to 50 msec. Of the 20 VPL neurons tested during SI stimulation, the average response to T stimulation was decreased a mean of 36%, with the suppression peaking (at 49% inhibition of the afferent response) about 15 msec after the C stimulus. Considerable rostrocaudal variation was observed, however. Whereas neurons in the rostral VPL (near VL) were strongly inhibited (-69%), neurons in the middle and caudal VPL exhibited facilitations at long and short C-T intervals, respectively. This study establishes a specific projection system from the forepaw region of SI cortex to different subregions of the VPL thalamus, producing specific temporal patterns of sensory modulation.

Afferent Pathways↗
PubMed1989

Sex steroids modulate motor-correlated increases in cerebellar discharge.

Adult female rats implanted with a microelectrode drive unit were trained to walk on a computer-controlled treadmill apparatus (10 s on every 20 s for 2 h) during recording of single Purkinje neurons in the paravermal area of the anterior cerebellum. Vigorous increases in the firing rate of individual units were found to be correlated with movement of specific limbs in particular stages of the step cycle during treadmill locomotion. Both spontaneous and motor-evoked discharge of individual Purkinje neurons were monitored before and after s.c. injection of either 17 beta estradiol (E2, 100 ng/kg) or progesterone (P, 50 micrograms). The percent increase in firing rate during locomotion versus rest was determined as a measure of the evoked:spontaneous discharge ratio. Drug-induced changes in this ratio indicate differential effects on the individual parameters, rather than simple excitatory or inhibitory effects. For all neurons tested, E2 augmented the movement-evoked discharge over pre-E2 control levels. The onset for this effect occurred at 15 min post-steroid, with a peak response noted at 30-35 min post-steroid. By 60-90 min, a partial recovery of the evoked:spontaneous ratio was noted, although absolute increases in both parameters were still observed, indicating long-term effects on neuronal activity. These effects were independent of the stage of the estrous cycle. In contrast, P decreased absolute firing rates of Purkinje cells during stationary and locomotor phases. However, the evoked:spontaneous ratio was decreased to an even greater degree. The latency for this effect was 9-12 min, with recovery to control levels of response seen at 30 min post-steroid. This response was typical of cells tested on estrus and diestrus 1. Cells tested on proestrus or diestrus 2, when E2 levels are increasing, were not modulated by P using the above paradigm.

Action Potentials↗
PubMed1989

Mapping the effects of motor cortex stimulation on single neurons in the dorsal column nuclei in the rat: direct responses and afferent modulation.

The major aim of this study was to define the topography of descending motor cortical influences on the dorsal column nuclei of the rat. A total of 1442 single neurons were recorded throughout the rat cuneate (Cu) or external cuneate (ECu) nuclei and classified according to their: 1) location within the nuclei, 2) receptive fields, and 3) response to standardized deep layer microstimulation in the forelimb area of the motor (MI) cortex. Excitatory neuronal responses to this MI cortical stimulation ranged in latency from 2-28 msec, with 80% of responses in the 4-12 msec range. Overall, the rostral extremity of the Cu (0.5-1.0 mm rostral to the obex), and the ECu contained the highest percentage of recorded neurons responding to the MI cortical stimulation (61%). By contrast, only 11% responded in the middle subregion of the Cu (+0.4 to -0.9 mm relative to the obex), and 28% responded in the caudal-most subregion (1.0-2.0 mm caudal to obex). A similar paradigm was used to investigate the topography of MI corticofugal modulation of afferent transmission through the Cu and ECu. The MI cortical stimulation was used as a conditioning (C) stimulus in a condition-test (C-T) paradigm in which the test (T) stimulus was standardized mechanical vibration of digit No. 4 of the contralateral forepaw. A total of 30 cells from different subregions were analyzed by measuring the averaged evoked unit responses to the T-stimuli, and plotting them as a function of C-T intervals from 0-50 msec.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1989

Ethanol withdrawal increases sensory responsiveness of single somatosensory cortical neurons in the awake, behaving rat.

This study investigated the effects of ethanol withdrawal on sensory responses of single neurons recorded in the somatosensory (SI) cortex of awake, behaving, ethanol-dependent rats. Eleven rats were fed an ethanol-containing liquid diet for 90-120 days, while 11 weight-matched controls were pair-fed an equivalent sucrose containing diet to equalize caloric intake. Single SI cortical neurons in the chronically treated rats were recorded continuously over several hours after withdrawal from ethanol, and after reintoxication induced by intraperitoneal injection of 10% (v/v) ethanol solution. Intoxication and withdrawal related changes in sensory responsiveness of these neurons were quantitatively measured by stimulating through electrodes chronically implanted under the skin of the forepaw. Sensory response histograms constructed from these stimuli showed a characteristic pattern, typically consisting of two early excitatory peaks (E1a and E1b), followed by an inhibition (I1), and in some neurons, a late excitatory response (E2). As withdrawal advanced, the sensory response histograms exhibited marked increases in the magnitudes of the E1a, I1, and E2 responses, coupled with a reduced spontaneous discharge rate. These changes are similar to, but quantitatively greater than, those which have previously been observed in normal and control rats during "immobile arousal" behaviors, which can be evoked when an experimenter holds the animals still, producing an immobile "aversive arousal." In withdrawing animals this same "holding" manipulation tended to markedly exacerbate and accelerate behavioral and neurophysiological signs of withdrawal. By contrast, the same manipulations had little effect when carried out during light intoxication or early stages of withdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcohol Withdrawal Delirium↗
PubMed1988

Electrophysiological actions of norepinephrine in rat lateral hypothalamus. II. An in vitro study of the effects of iontophoretically applied norepinephrine on LH neuronal responses to gamma-aminobutyric acid (GABA).

The preceding studies demonstrated that norepinephrine (NE) can consistently augment synaptically mediated (70%) and gamma-aminobutyric acid (GABA)-induced (69%) inhibitory responses of lateral hypothalamic (LH) neurons in vivo. The present experiments further characterized the interactions of NE with LH neuronal responses to GABA in terms of alpha- and beta-receptor mechanisms and demonstrated the utility of the in vitro LH tissue slice preparation as a model for future extra- and intracellular studies of NE modulatory phenomena. Extracellular activity of LH cells was recorded from diencephalic slices (450 microns) incubated in artificial cerebrospinal fluid at 33 degrees C. Interactions between iontophoretically applied NE, isoproterenol (ISO) or phenylephrine (PE) and responses of LH neurons (n = 64) to GABA microiontophoresis were quantitated and characterized using computer-generated ratemeter and histogram records. This analysis revealed two distinct actions of NE on GABA-induced responses of LH neurons. In 8 of 32 cells tested (25%), locally applied NE markedly enhanced inhibitory responses to GABA iontophoresis in a manner identical to that observed in vivo. However, in 20 cells (62.5%), iontophoretic application of NE produced a clear antagonism of GABA responses. NE also exerted dual effects on the background firing rate of LH neurons, causing both inhibition and excitation. Overall, in those cells where NE administration increased spontaneous discharge, it either antagonized or had no effect on GABA-mediated inhibition. In contrast, spontaneous firing rate was never elevated above control levels in those cases where NE potentiated GABA responses. Additional experiments demonstrated that the GABA potentiating actions of the benzodiazepine, flurazepam, were preserved in LH tissue slice preparations. In addition, iontophoretic application of the beta-agonist, ISO, routinely suppressed the spontaneous activity of LH neurons and mimicked the facilitating action of NE on GABA. Likewise, microiontophoretic application of 8-bromo cyclic adenosine monophosphate (AMP) enhanced GABA-induced inhibition of LH firing rate in each of 11 cells tested. On the other hand, local administration of the alpha agonist, PE, routinely produced NE-like antagonism of GABA inhibition along with increases in spontaneous firing rate. Taken together these findings indicate that the commonly observed in vivo phenomena of NE augmentation of GABA and suppression of LH neuron spontaneous firing can be demonstrated in vitro, and most likely result from activation of beta adrenoceptors and subsequent elevation of cyclic AMP levels.(ABSTRACT TRUNCATED AT 400 WORDS)

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1987

Corticocortical connections within the primary somatosensory cortex of the rat.

Corticocortical connections within the primary somatosensory (SI) cortex of rat were investigated by using discrete injections of retro- and orthogradely transported neuroanatomical tracers (including HRP, WGA, PHA-L, and 3H-leucine). Tangential and vertical connections were defined with respect to the cytoarchitectonic divisions within the rat SI, specifically: (1) the "granular zones" (GZs), characterized by their dense layer IV granular aggregates, which receive the majority of direct ventroposterior (VP) thalamocortical terminations, (2) the "perigranular zones" (PGZs), the less-granular cortical matrix just surrounding the GZs, and (3) the "dysgranular zones" (DZs), the larger dysgranular regions lying centrally within and just lateral to the SI. Receptive fields recorded in the granular zones are small and discrete, whereas in the perigranular zones and especially in dysgranular zones they exhibit complex sensory convergence. A major aim of this study was to determine whether the pattern of intracortical connectivity within the SI is compatible with these observed physiological differences. In general, the perigranular and dysgranular zones contained more profuse systems of corticocortical connections than did the granular zones. For example, discrete tracer injections in the perigranular zones produced "walls" of labelling throughout the adjacent perigranular zones, while adjacent granular zones were relatively empty. Nevertheless, the granular zones were filled with dendritic branches of neurons in adjacent perigranular zones. Since these dendrites could presumably receive direct VP thalamocortical contacts, they represent one path through which this thalamic sensory information might be transmitted to the perigranular zones. Further transmission to the dysgranular zones might be subserved by a topographically organized system of reciprocal interconnections that was found between the perigranular zones and dysgranular zones. In coronal sections, labelling produced by relatively distant injections of either retro or orthograde tracers generally appeared in a columnar distribution, and was localized in perigranular zones and dysgranular zones. Within these zones, orthograde labelling consisted of vertically oriented axons emitting collateral sprays of terminals in all layers. Retrograde neuronal labelling (composed almost exclusively of pyramidal cells) was greatest in supragranular layers. Proximal to the injection site, labelling tended to spread out from these columns into supra- and infragranular layers in adjacent granular zones.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1987

Progesterone alters GABA and glutamate responsiveness: a possible mechanism for its anxiolytic action.

In this study, the neuromodulatory effects of progesterone were tested in an intact neuronal circuit of a model extrahypothalamic CNS area. Spontaneous discharge and responses of single cerebellar Purkinje neurons to microiontophoretically applied gamma-aminobutyric acid (GABA) and glutamate were monitored before, during and after either systemic injection, at physiologic doses, or local application of the steroid. By both means of administration, progesterone significantly enhanced inhibitory responses of Purkinje cells to GABA and suppressed glutamate excitation within 3-10 min post-steroid. These results are consistent with the anxiolytic actions of the steroid.

Animals↗
PubMed1987

A paradigm for determination of direct drug-induced modulatory alterations in Purkinje cell activity during treadmill locomotion.

This paper describes a paradigm employing chronic single unit recording techniques and videotape analysis of treadmill locomotion in order to determine drug-induced modulation of sensorimotor neuronal activity. Animals implanted with a chronic headstage microdrive unit and an indwelling jugular cannula are trained to walk on a treadmill (10 s on, 10 s off). Characteristically, cerebellar Purkinje cells recorded 1-1.5 mm from midline, exhibit increased rates of discharge in phase with movement of specific limbs during a particular stage of the step-swing cycle, as assessed by video analysis of locomotor patterns. Drug-induced alterations in this movement-correlated discharge relative to changes in the spontaneous firing rate can then be determined to assess drug-induced neuromodulatory effects beyond general non-specific excitatory or inhibitory actions.

Action Potentials↗
PubMed1986

Laminar differences in sizes, shapes, and response profiles of cutaneous receptive fields in the rat SI cortex.

Quantitative techniques were used to demonstrate cortical layer differences in cutaneous receptive fields (RF's) in the rat SI cortex. Two- and three-dimensional (2-D and 3-D) RF maps were constructed showing the responsiveness of single neurons to standardized punctate stimulation of each of a matrix of points on the skin or the mystacial vibrissa pad. These allowed a visualization not only of the overall sizes of such RF's, but also their shape and "response profile". Initial experiments showed that the sizes and response profiles of such RF's were similar whether they were mapped by sinusoidal mechanical vibration of skin, punctate touch, or direct intracutaneous electrical stimulation. This method was used to quantitatively determine distoproximal lengths of RF's of single units recorded at different depths in the forepaw area of the SI cortex. Plots of these RF lengths as a function of cortical depth showed that the smallest RF's were found in the granular layers (IV and deep III). RF's up to double that size were found in supragranular layers, and up to triple that size in infragranular layers. 3-D maps of RF's in the granular layers showed sharp central response peaks surrounded by very steep dropoffs to the RF boundaries. In the whisker areas, granular layer RF's were typically circular in shape and contained from 1-4 whiskers. By contrast, in supragranular layers they were often elongated in shape, and were oriented along rows or columns of whiskers. RF's in layer V resembled large, high plateaus, often supporting clearly separated peaks. RF's mapped in the fore- and hindpaw areas were similar, but, even in the granular layers, were often slightly elongated along the limb axis. In all regions of the SI, both the locations and shapes of the granular layer RF's appeared to be conserved as subsets of other more topographically heterogeneous RF's encountered elsewhere in the column. These findings may correlate with patterns of axonal connectivity in the rat SI.

Afferent Pathways↗
PubMed1986

Distribution of somatic sensory and active-movement neuronal discharge properties in the MI-SI cortical border area in the rat.

The rat somatosensory (SI) cortex contains a precise map of the cutaneous periphery, yet its rostromedial edge, which includes part of the fore- and hind paw representation, has been reported to functionally overlap with the electrically excitable primary motor (MI) cortex. Thus, the MI cortex in the rat contains two subregions: (i) rostrally, the "MI-agranular" cortex (i.e., "typical" MI cortex), and (ii) caudally, the "MI-SI-granular" cortex (i.e., the MI-SI overlap). The aim of this study was to assess the degree of overlap in the physiologic properties of single neurons recorded across the MI-SI boundary zone in awake, freely moving rats. Computer techniques were used to characterize both somatosensory receptive fields (cutaneous or "passive joint-manipulation") and discharge correlates of active limb movement in these MI-agranular and MI-SI-granular subregions of the MI. "Active-movement" units were defined as those which discharged strongly in correlation with specific limb movements, but in a manner which could not be predicted by their observable somatosensory properties. Of 92 completely analyzed cells in the MI-SI-granular forepaw region, 86 exhibited specific cutaneous receptive fields on the palmar surface of the forepaw. By contrast with the similarity of these neurons' responses to passive stimulation, they varied markedly in their discharge during active limb movements. For example, many did not respond when their forepaw receptive fields touched the ground during stepping. Furthermore, 31 (of 92) neurons in this region were identified as active-movement, firing in correlation with reaching movements of the forelimb. Seven of these were completely unresponsive to any sensory stimuli, but 24 exhibited an apparent convergence of cutaneous and active-movement properties. Of 86 units recorded in the MI-agranular subregion, 46 responded strongly to passive joint manipulation, but only three responded exclusively to cutaneous stimulation. Twenty-eight (of 86) cells were defined as active-movement, discharging mainly in correlation with forelimb reaching movements. Thus, the active-movement properties of neurons in these two subregions were quite similar, whereas the somatosensory properties were markedly different.

Animals↗
PubMed1986

Acute ethanol effects on sensory responses of single units in the somatosensory cortex of rats during different behavioral states.

We have investigated the dose-dependence and time-course of ethanol effects on the activity of single neurons in the somatosensory (SI) cortex of behaving, unanesthetized rats. Sensory responses of neurons recorded in the forepaw area of the SI cortex were quantitatively measured by constructing post-stimulus histograms to repetitive stimulation through electrodes chronically implanted in the forepaw. Single units were isolated and held throughout a protocol involving: (1) a control period, (2) intoxication produced by a single dose of ethanol administered IP or IV and (3) recovery for 60 minutes or more. Post-stimulus histograms were generated during three standard behaviors: (1) REST, (2) IMMOBILE AROUSAL (produced by holding the animal), and (3) MOVEMENT (running on a treadmill). In pre-ethanol controls, the immobile arousal condition slightly increased both excitatory and inhibitory components of the sensory response, while the movement condition strongly inhibited them. Ethanol reduced both of these types of behavioral modulation of sensory responses by abolishing the facilitation normally seen during immobile arousal, as well as the inhibitory gating normally seen during movement. Different latency response epochs of post-stimulus histograms were also used to compare the effect of ethanol on fast vs. slow conducting pathways to the SI cortex. Ethanol at low doses (0.3 g/kg bw, IP) was found to selectively reduce the longer latency excitatory response peaks, while sparing the shortest latency response peak. At moderate doses (1.0 g/kg), however, the shortest latency response peak was also reduced. This contrasted with the effects of halothane which, at anesthetic doses, exerted a much more selective reduction of the longer latency responses.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1984

Mapping the body representation in the SI cortex of anesthetized and awake rats.

We have used single unit recording techniques to map the representation of cutaneous and joint somatosensory modalities in the primary somatosensory (SI) cortex of both anesthetized and awake rats. The cytoarchitectonic zones within the rat SI were divided into the following main categories: (1) granular zones (GZs)--areas exhibiting koniocortical cytoarchitecture (i.e., containing dense aggregates of layer IV granule cells), (2) perigranular zones (PGZs)--narrow strips of less granular cortex surrounding the GZs, and (3) dysgranular zones (DZs)--large areas of dysgranular cortex enclosed within the SI. The narrow strip between the SI and the rostrally adjacent frontal agranular cortex was termed the "transitional zone" (TZ). Initial computer-based studies of the properties of cutaneous receptive fields (RFs) in SI showed that, although there were differences in response threshold, adaptability, frequency response, and overall RF size and shape of adjacent neurons, the size and location of the "centers" of the RFs were quite constant and were similar to those seen in multiple unit recordings. The same was true of RFs of single neurons recorded through different anesthetic states. The body representation in SI was first mapped by determining single unit and unit cluster RFs within a total of 2,170 microelectrode penetrations in barbiturate-anesthetized rats. Cutaneous RFs in the GZs were quite discrete. Thus, a single, finely detailed, continuous map of the cutaneous periphery was definable within the GZs themselves. Only the forepaw had a double representation. RFs in the PGZs were larger and more diffuse, but since they covered roughly the same skin areas as the RFs in the most closely adjacent GZs, they fit into the same body map. Neurons in the DZs were unresponsive to any sensory stimuli in the anesthetized animal. In chronically implanted, freely moving, awake animals cutaneous RFs were larger and more volatile than in the anesthetized, but the accuracy of the map was clearly preserved by the fact that the locations of the RF centers (which often must be defined quantitatively) were unchanged. The PGZs and DZs in the awake animals exhibited a multimodal convergence of cutaneous and joint movement RFs within single vertical penetrations, or even on single neurons. Directionally specific and bilateral cutaneous RFs were also observed in the DZs. It was concluded the DZs are more associational or integrative areas within the SI, but they could not be shown to comprise a distinct and separate body representation.(ABSTRACT TRUNCATED AT 400 WORDS)

Anesthesia, General↗
PubMed1983

Ethanol's effect on selective gating of somatic sensory inputs to single cortical neurons.

The effect of alcohol intoxication was tested on sensory responses of single units in the somatosensory (SI) cortex of awake, freely moving rats. We have previously shown that transmission of cutaneous sensory information from the paw to the cortex during movement is subject to a time varying pattern of sensory suppression which selectively "gates in" sensory information to particular categories of cortical neurons during certain phases of the locomotor step cycle. In the period of 5-20 minutes after alcohol administration (when the rats became hyperactive) the afferent inhibition producing this selective gating was reduced or abolished, depending on the ethanol dose (between 0.75 and 1.5 g/kg). This indicates that the selective suppression of "irrelevant" inputs to certain cortical cells, which is normally seen during movement, is absent during alcohol intoxication. This paradigm may provide a model for study of the neurophysiologic mechanism by which alcohol disturbs higher cognitive functions involving cortical management of sensorimotor tasks.

Animals↗