Evoked potentials and unit activity in the cat somatosensory cortex

Investigation of unit activity of the cat somatosensory cortex has shown that the principal role in the genesis of the primary response, the response to stimulation of the thalamic relay nucleus, the callosal response, and certain other forms of evoked potentials (EPs) of the somatosensory cortex is played by neurons not usually responding by spike generation during EP development. The EPs reflect what the cortical neurons received from the afferent volley, and the level of their polarization, but they are not a reliable indicator of fast nervous processes in the cerebral cortex. The EPs reflect postsynaptic potentials (PSPs) of neurons not directly participating actively in the analysis of information reaching the cortex.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 2, No, 4, pp. 360–367, July–August, 1970.     

Connections between the frontal and parietal areas of the cerebral cortex and the caudate nucleus in the cat]

In 10 cats with aseptically extirpated frontal and parietal areas of the brain cortex, efferent connections of the areas in question with the nucleus caudatus were experimentally studied by means of morphological methods. The preparations were stained according the methods of Nauta, Knuck, Finck-Haimer, and Kawamura-Niimi. The results of the investigations performed demonstrate a perfect topically organized caudal projection of the "associative" cortical areas. The frontal area is projected on the oral ventro-medial parts of the nucleus caudatus head, while the parietal area--on the central and lateral parts at the medial and more caudal levels.     

Response activity of different areas of the associative region of the cerebral cortex in the cat

In cats we have simultaneously (monopolarly) recorded the responses in different parts of the associative cortex (ac) (motor cortex, proreal, orbital, anterior marginal, and mid-part of the suprasylvian gyri) appearing for different peripheral stimulations (stimulation of the skin of the forelimbs, a light flash and a sound click). In all the regions of the ac associative responses (ar) almost identical in configuration appeared to all the peripheral stimulations. The ar of the orbitofrontal and the motor cortex differed from the ar of the suprasylvian gyrus in the shorter latent period and greater stability. In each part of the ac we found the same focus of maximum activity for all the peripheral stimulations. For paired stimulations of the same and different modalities the greatest stability in relation to the blocking influence due to the conditioning stimulation characterized the ar which appeared in response to skin stimulation in the orbitofrontal cortex and the ar which appeared in the suprasylvian gyrus on exposure to a light flash. It is assumed that in the orbitofrontal cortex an efferent discharge is formed in response to pulses of different sensory modality whereas in the suprasylvian gyrus there is only sensory integration. Some aspects of afferent convergence are discussed.Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 2, No. 2, pp. 126–139, March–April, 1970.     

Rhythmic after-discharge in the cat cerebral cortex and deep brain structures during stimulation of the claustrum

Effects of stimulation of the claustrum and caudate nucleus in the neocortex and various deep brain structures were studied in acute experiments on unanesthetized cats immobilized with tubocurarine. A rhythmic after discharge appeared in neocortical areas 4–7 and 18 (according to Reinoso-Suarez' atlas), and also in the caudate nucleus and various parts of the thalamus. A similar discharge also was observed in the claustrum itself. Diencephalic brain section at the level of the ventral anterior nucleus weakened but did not completely abolish the cortical rhythmic after-discharge in the anterior regions of the neocortex evoked by stimulation of the claustrum. This discharge was completely blocked after sagittal brain section between the claustrum and the rest of the thalamus.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 15, No. 2, pp. 121–127, March–April, 1983.     

Evoked potentials of the cerebral cortex during the comparison of visual stimuli

Visual evoked potentials (EP) were recorded when the test subjects accomplished the tasks of a comparison of a current stimulus with the previous one, the stimuli being presented in a continuous sequence. In the first task, rare repetition of two stimuli (Russian letters) in the continuously changing flow of stimuli was relevant, and the test subject had to press the button when it happened; in the second task, the relevant stimulus was a rare change in the flow of stimuli. The influence of the stimulus repetition/change factor on EP was analyzed. The processes related to the comparison of the current and previous stimuli were most manifest in four time intervals: 120–140, 180–210, 260–280, and 350–370 ms. The occipito-temporal component of EP revealed in the interval of 180–210 ms, which we denoted as the negative component of visual mismatch (NCVM), proved a special component, differing in its functional and temporal characteristics from theN _2b component. WhereasN _2b is modulated by the factor of stimulus probability, the NCVM by that of stimulus repetition/change.     

Postsynaptic neuronal response of a cat sensorimotor cortex during evoked and self-sustained rhythmic "spike and wave" activity

Intracellular correlates of complex sets of rhythmic cortical "spike and wave" potentials evoked in sensorimotor cortex and of self-sustained rhythmic "spike and wave" activity were examined during acute experiments on cats immobilized by myorelaxants. Rhythmic spike-wave activity was produced by stimulating the thalamic relay (ventroposterolateral) nucleus (VPLN) at the rate of 3 Hz; self-sustained afterdischarges were recorded following 8–14 Hz stimulation of the same nucleus. Components of the spike and wave afterdischarge mainly correspond to the paroxysmal depolarizing shifts of the membrane potential of cortical neurons in length. After cessation of self-sustained spike and wave activity, prolonged hyperpolarization accompanied by inhibition of spike discharges and subsequent reinstatement of background activity was observed in cortical neurons. It is postulated that the negative slow wave of induced spike and wave activity as well as slow negative potentials of direct cortical and primary response reflect IPSP in more deep-lying areas of the cell bodies, while the wave of self-sustained rhythmic activity is due to paroxysmal depolarizing shifts in the membrane potential of cortical neurons.I. S. Beritashvili Institute of Physiology, Academy of Sciences of the Georgian SSR, Tbilisi. Translated from Neirofiziologiya, Vol. 18, No. 3, pp. 298–306, May–June, 1986.