Sensomotor Cortex Research Articles

Action of strychine on evoked potentials and postsynaptic responses of cat sensomotor cortical neurons

Acute experiments on immobilized cats lightly anesthetized with pentobarbital showed that application of strychine to the cortical surface inhibits slow negative potentials arising during direct and primary responses of the sensomotor cortex and corresponding IPSPs in pyramidal neurons. Iontophoretic applications of strychine blocks predominantly the early component of the IPSP, during which the input resistance under normal conditions is significantly less than during the late component of the IPSP, indicating that these components differ in their genesis. It is concluded that individual components of cortical evoked potentials have a common genesis, and that the slow negative potential is the dipole reflection of the IPSP in pyramidal neurons; the early component of the IPSP, moreover, is generated as a result of activation of axo-somatic inhibitory synapses, whereas the late component is generated as a result of activation of axo-dendritic synapses. The mediators in these inhibitory synapses may be different.

Ultrastructure of neurons and interneuronal connections in the sensomotor cortex of progeny of alcohol-addicted rats

This paper studies the ultrastructure of neurons and interneuronal connections in the sensomotor cortex of the progeny of alcohol-addicted rats. Experiments were carried out on 12 female and four male albino rats; they were given alcohol solutions for 4 months and then mated. The female rats continued to ingest alcohol until the young rats acquired vision. The sensomotor cortex of experimental young rats aged 21 and 30 days and of intact animals of the same age was investigated; the sections were stained with uranyl acetate and studied. It is shown that alcoholic intoxication of females and males causes significant disturbances of the structural organization of the sensomotor cortex in the progeny.

Changes in neuronal trace responses of the sensomotor cortex and putamen induced by haloperidol

Changes in neuronal trace responses of the sensomotor cortex and putamen induced by haloperidol

Corticofugal influences on postsynaptic processes in rubrospinal neurons in the cat brain

Composite and unitary EPSPs of red nucleus neurons evoked by stimulation of the sensomotor and association parietal cortex and nucleus interpositus of the cerebellum were studied in acute experiments on cats anesthetized with pentobarbital. A monosynaptic connection was shown to exist between not only the sensomotor, but also the association cortex, and rubrospinal neurons, in which unitary EPSPs appeared during stimulation of the association cortex after a latent period of 1.5–2.7 msec, with a peak rise time of 1.1–3.1 msec and an amplitude of 0.22–0.65 mV. Analysis of the temporal characteristics of the unitary EPSP suggested that synapses formed by fibers from the association cortex occupy a position nearer the soma than synapses formed by axons of sensomotor cortical cells.

Effect of a dominant focus in the mesencephalic reticular formation on the functional state of the sensomotor cortex.

1. A dominant state formed in the mesencephalic reticular formation during high-frequency electrical stimulation of that structure had an influence on the functional state of the sensomotor cortex. This was manifested as a simultaneous statistically significant increase in amplitude of the evoked cortical potentials and in the number of motor responses to afferent stimuli used to reveal the dominant state. 2. Repeated stimulation of the retipular formation against the background of increased excitability of the CNS led to the formation of a pathological defensive dominant, expressed as manifestation of characteristic series of limb movements of the same kind, both to application of the stimuli and in the intervals between them. This state persisted for a long time during the work and also after an interval between experiments (lasting one month or more).

Interaction between spontaneously active cortical neurons during defensive conditioning.

1. During defensive conditioning to light in rabbits the level of statistical correlation between discharges of visual and sensomotor cortical neurons rose. The coefficient of cross-correlation, reflecting the degree of dependence of discharge of a visual neuron on the discharge of a sensomotor neuron and vice versa, increased on average to 1.2×10−2 from 7.1×10−3 in control animals. 2. The number of pairs of neurons (about 26%), one of which lay in the zone of the conditioned stimulus, the other in the zone of unconditioned stimulus, and between whose discharges significant functional connection was present, remained unchanged during defensive conditioning. 3. The level of correlation between the spontaneous discharge of neighboring neurons in the two regions of the cortex fell, especially in the visual cortex. In untrained animals the mean coefficients of cross-correlation of spontaneous activity of neighboring cells was 9.0×10−2 in the sensomotor cortex and 8.5×10−2 in the visual cortex. During conditioning they fell to 5.8×10−2 and 1.95×10−2 respectively.

Effect of injury to the neocortical association areas on visuomotor coordination in cats.

1. In a situation of visually controlled behavior a lesion of the projection area of the forelimb in the sensomotor cortex and total extirpation of the parietal cortex leads to a reduction in the number of correct test performances, lengthening of the searching time, and the change in the character of searching. 2. Partial injury to the parietal association cortex does not affect the number of correct test performances, and this is also true of removal of the frontal pole. In both cases changes in the character of searching and lengthening of the time required to achieve a position of the stimuli rewarded by reinforcement are observed. 3. Extirpation of the striate cortex has no effect on the ability of the animal to learn how to perform the test and causes no change in the strategy of searching.

Morphological and functional changes in sensomotor cortical synapses during the summation reflex in rabbits.

1. Electron-microscopic study of synapses in the rabbit sensomotor cortex during the summation reflex reveals structural changes in the pre- and postsynaptic components of axodendritic synapses, possibly as a result of increased functional activity of the synaptic apparatus. 2. The strongest response to a combination of stimuli is observed in the postsynaptic matrix, and it results in marked thickening of the postsynaptic membranes in some axo-dendritic synapses. 3. The character of ultrastructural changes in synapses in the sensomotor cortex during formation of simple forms of temporary connection makes it appear likely that the postsynaptic membrane of axo-dendritic synapses is one of the earliest sites of structural consolidation of traces of incoming information.

Effect of amygdalectomy on sensomotor cortical evoked potentials in cats.

1. Destruction of the amygdaloid body leads to disturbance of the dependence of the amplitude and probability of appearance of EP on the filling frequency of the tonal volley established in intact animals; maximal values of amplitude and probability of appearance of EP at frequencies of O.8 and 1.6 kHz and between 2.0 and 3.0 kHz are not found in amygdalectomized cats. 2. It is postulated that integrity of the amygdaloid body is an essential condition for the normal functioning of the sensomotor cortex, which is a component of the system distinguishing the biological significance of an acoustic stimulus.

Effect of inactivation of sensomotor cortical function by cold on unit activity in the head of the caudate nucleus.

Experiments with extirpation, cold inactivation, and electrical stimulation of the sensomotor cortex have demonstrated the existence of inhibitory influences of this structure on general motor activity and on various behavioral acts in animals [3, 4, 8]. Inhibitory influences of functional cold inactivation of the sensomotor cortex on spontaneous unit activity in the parietal cortex were demonstrated by the writer previously [1]. There is neurophysiological and morphological evidence of connections of this part of the neocortex with the caudate nucleus and, in particular, with its head [2]. It was interesting to study the effect of inactivation of the sensomotor cortex on spontaneous and evoked unit activity in the head of the caudate nucleus.

Structural and functional changes in neurons and glia in the sensomotor cortex in experimental neurosis.

1. In rabbits with experimental neurosis metabolic disturbances are found in the sensomotor cortex, and are reflected in a 26% increase in size of the nuclei of the large pyramidal neurons in layer V, and the appearance of pale and dark cells with stained basophilic substance, and acidophilic cells characteristic of a state of hypoxia. 2. The number of neurons with two, three, and four perineuronal satellites is increased; the number of neurons without satellites or with only one satellite is reduced. The reaction of the perineuronal glia is productive in character: The mean number of perineuronal satellites is increased by 26%; a considerable number of branched oligodendrogliocytes appeared. As a result of hypoxia the amount of total glia is reduced. 3. The development of extensive connections of all types of glia with neurons and blood vessels indicates active involvement of the glial cells in the process of compensation and repair. The distinctive features of response of the perineuronal, free glia, and the microglia confirm the view that the degree of participation of these cells in neuronal metabolism differs. 4. Histological and hypoxic changes found in neurons and neuroglia are evidence of the complex structural and metabolic changes taking place in vascular, neuronal, and neuroglial cells of the sensomotor cortex in this form of experimental pathology. The results can be used to further the study of mechanisms of compensation of disturbances of higher nervous activity and of pathogenetically based treatment.

Analysis of long-latency components of field potentials evoked by stimulation of the cerebral cortex and nerves in the cerebellar paramedian lobule

Field potentials evoked in the graunular layer of the cerebellar paramedian lobule of unanesthetized cats in response to stimulation of the sensomotor cortex and limb nerves contained slow negative waves, appearing after a long latent period, which were generated by granule cells. In the case of nerve stimulation this component was recorded both inside and outside the projection zone of the corresponding limb. Cortical stimulation by single stimuli or series of stimuli not more than 1.8–2.5 times above threshold strength led to the appearance of evoked potentials only inside the corresponding projection zone. The long-latency component of field potentials evoked by cerebral stimulation followed high frequencies of repetitive stimulation and was less sensitive to the action of barbital anesthesia than the analogous component of potentials evoked by nerve stimulation. In the case of combined cerebral and nerve stimulation the long-latency components underwent summation. It is concluded that mossy fibers of slowly-conducting spino- and cerebrocerebellar tracts innervate different granule cells in the cerebellar cortex.

Effect of opioid peptides, morphine, and electroacupuncture on unit activity in the sensomotor cortex and brain-stem reticular formation

Experiments were made on unanesthetized rabbits and cats to examine the neuronal response (the sensomotor cortex, mesencephalic reticular formation, giant cell reticular nucleus of the medulla oblongata) to microapplications of enkephalins, endorphins, morphine, and electroacupuncture. Opiate peptides, morphine, and electroacupuncture produced similar, unidirectional changes in both spontaneous and nociceptive-stimulated neuronal activity. Naloxone removed these reactions. It is assumed that in the brain structures under study, the electroacupuncture effects are mediated by opiate receptors and are linked with enkephalin and endorphin release.

Analysis of interaction between evoked potentials to stimuli of different modalities in the auditory, sensomotor, and visual cortex in cats.

1. By the use of a method of paired stimulation of different modalities (clicks and electrodermal stimulation of the orbicularis muscle), acting in two different orders — “clicks + EDS” and “EDS + clicks” — differences were found in the recovery cycles of global EPs recorded simultaneously in the auditory, sensomotor, and visual areas of the neocortex. In the auditory cortex, in response to stimulation applied in the order “clicks + EDS” and with short intervals between stimuli (20–70 msec) in the pair, a stage of complete blockade of EPs to testing EDS is observed; if stimulation is in the opposite order (“EDS + clicks”) the amplitude of EPs to testing clicks is independent of the previous action of EDS and commensurate with the amplitude of EPs to isolated clicks. In the sensomotor and visual areas of the cortex two EPs are recorded, one to clicks and one to EDS, during application of paired stimuli both in the “clicks + EDS” and “EDS + clicks” order. 2. Changes in EPs to paired stimulation described above characterized the functional organization of inputs to the cortical areas tested for clicks and EDS: In the auditory area functioning of the input for the inadequate nociceptive stimulus is wholly dependent on the presence or absence of previous afferentation from the adequate acoustic stimulus, whereas activation of the input for the adequate stimulus is relatively independent; in the sensomotor and visual areas functioning of the inputs for both stimuli is relatively independent.

Neocortical evoked responses and spike activity during startling in response to stimulation of the mesencephalic reticular formation.

1. Stimulation of the mesencephalic RF by a single pulse of current (of threshold strength for elicitation of the startle response) evoked a reticulocortical response (RCR) in the cortex (LP 2.5–3 msec) with a focus of maximal activity in the sensomotor cortex. The RCR recorded from the surface of the cortex is polyphasic and consists of early (a negative-positive complex) and late (negative and positive waves) components of the evoked response. RCRs from different regions of the cortex had a similar configuration but differed in the absolute and relative amplitude characteristics of the different phases. 2. Among the sensomotor cortical neurons with an initial response of excitation to stimulation of RF which were investigated (248 cells) two groups were distinguished. Neurons of the first group (136, LP 3–50 msec) showed correlation with the appearance of the various phases of the global surface potential: during development of the early and late negative phases of the RCR neurons in the upper level of the cortex (24.1 and 19.3% of neurons respectively) were involved in the response; the response of 25.5% of neurons in the lower layers correlated with the appearance of the early positive wave of the RCR. For neurons of the second group (112, LP > 50 msec) no correlation was found with waves of the cortical surface potential. Neurons with an initial inhibitory response (66 cells) changed their activity during recording of the early negative component of the RCR (lower level, 40.4% of neurons). During recording of the early positive potential, spike activity in neurons of the upper layers was slowed or ceased (19.7% of cells). 3. The results indicate that the flow of nonspecific impulses to the cortex along oligosynaptic pathways is destined mainly for cells in the upper level of the cortex. 4. It is postulated that the motor component of the unconditioned startle response arising to stimulation of RF may be triggered from subcortical structures.

Late components of evoked potentials in cortical projections of paired stimuli during food conditioning to electrical stimulation of the lateral geniculate body.

1. The possibility of formation of a conditioned food reflex to stimulation of the lateral geniculate body (LGB) was demonstrated and its features are described. 2. Formation of a conditioned reflex to stimulation of LGB is accompanied by the appearance of intensification of the late positive-negative component of EP in the visual and sensomotor cortex, with similar configuration. The peak latency of the negative component in the cortical areas studied was 40–80 msec. 3. The amplitude of the late positive-negative complex of the EP in the cortical areas studied differs during periods of isolated and paired action of the conditioned and reinforcing stimuli.

Analysis of cross-correlation functions of cortical unit activity.

1. Analysis of forms of cross-correlograms of activity of adjacent cerebral cortical neurons shows that about 85% of extreme on these graphs are symmetrically arranged relative to the origin of coordinates and that their mean width is about 30 msec. It is suggested that the main factor determining the relatively high and stable level of coordination between discharges of neighboring cortical cells is the effect of a common source, causing parallel changes in the membrane potential levels of these cells. 2. The ratio between the numbers of symmetrical and asymmetrical extreme on cross-eorrelograms of activity of remote neurons in the visual and sensomotor cortex is about 1:1. Repetitive photic stimulation changes the character of temporal relations between the discharges of these cells and the changes last at least i0 min after termination of stimulation. Aftereffects of afferent stimulation~ discovered on analysis of mutual relations between neurons in different cortical areas, indicate that synaptic connections may be present between them (including a number of intermediate cells); the effectiveness of these connections may be determined, moreover, by influences of nonspecific deep brain structures on the neocortex.

Effect of acoustic stress on the morphology of the rat sensomotor cortex

Effect of acoustic stress on the morphology of the rat sensomotor cortex

Effect of serotonin injected into the amygdala on conditioned and unconditioned food reflexes and the EEG in cats.

1. Microinjection of 5-HT into the basolateral region of the amygdala inhibits reproduction of motor conditioned food reflexes but does not affect unconditioned reflexes (the taking of food, the act of eating) or food motivation. 2. Microinjection of 5-HT into the basolateral region of the amygdala reduces spatial synchronization of potentials between the visual and sensomotor cortex and between the neocortex and hippocampus. 3. Under the influence of 5-HT injected into the basolateral region of the amygdala generation of periodic bursts of high-frequency activity (25–35 Hz) is blocked and a slow, irregular rhythm with a frequency of 4–8 Hz is recorded from the amygdala.

Effect of isolated and combined stimulation of thalamic nuclei on the character of functional connections between sensomotor cortical neurons.

1. Investigation of interneuronal relations in the cat sensomotor cortex revealed different types of dependence in the discharge of individual neuron pairs both during their spontaneous activity and in the after-period of thalamic stimulations. 2. Repeated isolated stimulations of the thalamic nuclei (VPL and VL) led to marked transformation of the “excitatory” component of the “inhibitory—excitatory” relationship dur1ing discharge of two neighboring neurons. The transformations differed in cases of stimula tion of the two different nuclei: whereas stimulation of VPL mainly weakened the “excitatory” component of the “inhibitory—excitatory connection,” stimulation of VL usually distinctly enhanced it. 3. The character of interneuronal influences formed during the action of isolated thalamic stimulations underwent further modification in the course of combined stimulations of the same nuclei. 4. Changes in interneuronal dependence arising as a result of prolonged thalamic stimulation could last for several minutes after cessation of the stimulations.