Synaptic reactions of sensomotor cortex neurons to stimulation of emotionally significant brain structures

The study deals with synaptic and spike responses of neurones in the rat sensorimotor cortex to stimulation of the lateral and medial hypothalamus, locus coeruleus and raphe nuclei. The activity of 57 neurones was recorded, 41 of them intracellularly and quasi-intracellularly, in response to the stimulation of sites in these structures, which were previously identified as "emotionally/ significant. No considerable differences in the effects of the stimulation of different "emotiogenic" zones were found. The stimulation parameters, differing from the "behavioural" ones by a greater strength, elicited in the majority of neurones clear post-synaptic responses, often in the form of EPSP-IPSP. Latencies of the responses varied from 3 to 80 msec. The most stable and pronounced responses were obtained to the stimulation of the lateral hypothalamus. No significant correlations of the latencies of the responses to the stimulation of different "emotiogenic" structures were found.     

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.     

Unit responses of the sensomotor cortex to paired electrical stimuli

Unit responses of the sensomotor cortex to paired electrical stimulation and visual cortex, applied either simultaneously or after various delays (from 0 to 200 msec) depend on the order of application of the stimuli and on the interval between them. If stimulation of the sensomotor cortex was used in a conditioning role the response continued unchanged when the intervals between stimuli were increased to 200 msec. If, however, stimulation of the sensomotor cortex had a testing role interaction was observed between the stimuli so that responses to both first and second stimuli were blocked; this was exhibited most clearly for intervals of 40–80 msec between stimuli. The blocking effect persisted on some neurons with delays of up to 200 msec between stimuli, while the response of others to both the first and the second stimulus was restored.Institute of Higher Nervous Activity and Neurophysiology, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 5, No. 6, pp. 628–635, November–December, 1973.     

Post-tetanic strengthening of evoked electrical responses of the sensomotor cortex]

A study has been made of the posttetanic potentiation of evoked potentials (PTP EP) in the sensorimotor cortex, appearing in response to VPL stimulation. A distinct PTP EP of the cortical surface has been found as well as considerable differences in its intensity recorded at different portions of deep cortical layers (700 to 1600 mu). Suggestions were made regarding the origin of the phenomena observed.     

Inhibitory influence of supplementary extraneous stimulation upon neuronal responses in the sensorimotor cortex of the cat during a conditioned reflex

Using alert rabbits trained to perform placing movements in response to a sound click, we investigated impulse responses (IR) of neurons of the somatosensory cortex preceding realization of the reflex by 50–150 msec. When a brief extraneous stimulation (light flashes, audible tone, electrical stimulation of a limb) was applied after initiation of the reflex, learned movements with the earlier behavioral parameters (latent periods and duration) were maintained. However, the IR of neurons to the presentation of a conditioned stimulus (CS) was of lesser intensity and arose 50–250 msec later. A constant extraneous stimulation (an audible tone, a forced stream of air upon the muzzle) or a decrease in the intensity of the CS administered to the threshold of hearing resulted in similar changes in the neuronal responses upon the application of the CS, but the parameters of the learned movements were maintained. We suggest that the cause of these changes in neuronal responses is increased exteroceptive attention to extraneous stimulation to additional extraneous stimulation.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziologiya, Vol. 23, No. 2, pp. 174–181, March–April, 1991.     

Electrical activity of the limbic structures of the dog brain during simultaneous stimulation of the cingulate gyrus and hypothalamus]

Simultaneous electrical stimulation of the anterior part of the cingulate gyrus and the anterior-lateral part of the hypothalamus in the dog brought about EEG synchronization in the limbic system structures and increased correlation coefficients between them. The animal's behaviour exhibited positive emotionally reactions (licking, sniffing, wagging the tail), attended with slowing of the heart rate. The indicated changes directly depend on the degree of emotional stress (the changes are more pronounced in hungry than in sated animals). Simultaneous stimulation of the anterior part of the cingulate gyrus and the anterior-lateral part of the hypothalamus apparently activates a system which reduces the level of emotional stress.     

Auditory brain stem responses to monoaural stimulation registered in symmetrical areas of cat's brain cortex

In five anaesthetized cats (Nembutal 35 mg/kg) with 14 chronically implanted recording epidural electrodes the auditory brain stem responses (ABR) to monoaural stimulation (click) in symmetrical areas of the brain cortex were recorded. Each ABR to acoustic stimulus of sufficient intensity is formed by a complex of alternating five positive (P1-P5) and four negative (N1-N4) peaks; two further small peaks often follow on this complex. The amplitude of ABR peaks N3, P4, N4 and P5 to monoaural stimulation in symmetrical areas of cat's cortex was always higher in records from the hemisphere contralateral to the stimulated ear than in records from the ipsilateral one. The amplitude of P3 ABR peak behaved to the contrary--it was higher on ipsilateral hemisphere. On the other hand the amplitude of ABR peaks P1, N1, P2 and N2 to monoaural stimulation in symmetrical areas of the brain cortex showed no degree of lateralization in our experimental animals. The present findings support indirectly the presumption that each peak of the ABR is generated by a particular acoustic brain stem structure.     

Changes in pyramidal tract response to direct stimulation of the sensomotor cortex of the rabbit during formation of a conditioned reflex

Changes of pyramidal tract (PT) response were analyzed, reflecting the final result of cortical interaction in the process of combinations of direct stimulations of cortical surface in nonimmobilized and unanaesthetized rabbits. It has been shown that in a situation, modelling conditioning, changes take place of the first direct component--the D-component--of the PT response (reflecting the excitability of the PT neurones), as well as changes of the successive indirect synaptic component--I-component (reflecting the excitability of presynaptic cortical elements and of intracortical synaptic connections). I-component changes were significantly more expressed. In most cases the I-component of the response was increased. The obtained data testify to an increase of synaptic efficiency in the process of temporary connection formation and to possible change (increase or reduction) of excitability of PT neurones.     

Formation of "caudate spindles" in the rabbit sensomotor cortex during ontogeny

Electrical activity of the sensomotor and visual areas of the neocortex during stimulation of the caudate nucleus was recorded in young rabbits aged 3–60 days and in adults. Single stimulation of the caudate nucleus was found to cause the appearance of characteristic bursts of spindle-like rhythmic activity ("caudate spindles"), described previously in cats and monkeys, in the adult rabbit cortex. The latent period of the caudate spindle was about 200 msec, its duration 1–3 sec, and the frequency of its oscillations of the order of 12 Hz. Caudate spindles were most marked in the sensomotor cortex of the ipsilateral hemisphere. In rabbits under 10 days old caudate spindles were not found even if the intensity of stimulation was increased many times. Starting from the age of 15 days bursts of rhythmic activity resembling caudate spindles, but with lower frequency (about 8 Hz), longer latent period (up to 350 msec), and also with a higher threshold, appeared in the sensomotor cortex. The definitive type of caudate spindles was established toward the end of the first month of postnatal life, corresponding to the time of formation and complication of conditioned-reflex activity in developing animals.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 17, No. 1, pp. 11–15, March, 1985.     

Inhibitory effects of external stimulation on neuronal spike response in the cat association cortex during conditioning

The effects of external stimulus presentation on neuronal spike response induced in area 7 by conditioned and unconditioned stimuli were investigated in waking cats. Pointing reaction arising in response to the action of external stimuli led to the phasing out of spike response to unconditioned cutaneous stimulation, as well as depression or complete suppression of response in area 7 neurons to conditioned stimulus presentation, despite occurrence of conditioned reflex motion. External stimuli no longer exerted an inhibitory effect on the neuronal spike response induced by protracted use of conditioned and unconditioned stimuli. The fact that the conditioned lever-pressing reflex could occur either following or without neuronal spike response in area 7 would raise the question of whether neurons belonging to this area always participate directly in the triggering and occurrence of conditioned reflex motion.A. A. Bogomolets Institute of Physiology, Academy of Sciences of the Ukrainian SSR, Kiev. Translated from Neirofiziogiya, Vol. 22, No. 2, pp. 147–155, March–April, 1990.     

Primary neuronal inhibitory responses of a chronically isolated slab of auditory cortex to intracortical stimulation in cats

Responses of 579 neurons in a slab of cerebral cortex (3 weeks after its isolation) to intracortical stimulation, with a distance of 0.5, 1.0, and 2.0 mm between recording and stimulating electrodes, were tested intercellularly and histological changes in a similar slab were studied in experiments on cats. Primary IPSPs were shown to develop in the chronically isolated slab in a much larger number of neurons than in the acutely isolated slab. Latent periods of IPSPs in all series of experiments did not exceed 10 msec, and most IPSPs were mono- and disynaptic. The amplitude and duration of the IPSPs were similar to those observed in the acutely isolated slab and intact auditory cortex in cats. It is concluded that local intracortical neuronal chains along which impulses evoking an inhibitory effect in the terminal neuron of the chain are transmitted are of relatively short length. Such chains may participate in local processing of incoming information. Analysis of the distribution of neurons responding by primary IPSPs by duration of their latent periods and depth in the slab in each series of experiments revealed a spatial and temporal mosaic of inhibitory responses in the chronically isolated slab of auditory cortex and showed that this mosaic is due to intracortical mechanisms.I. I. Mechnikov Odessa State University. Translated from Neirofiziologiya, Vol. 16, No. 2, pp. 152–161, March–April 1984.