[Rat brain reactions to acute brain stem lesion on dynamics of parameters of cerebral electric activity]. / Reaktsiia mozga krys na ostroe stvolovoe povrezhdenie v dinamike pokazatelei tserebral'noi élektricheskoi aktivnosti.

Despite an old history of a question, adaptive brain reactions that develop after an acute brainstem lesion have not been adequately investigated. With the aim to study the central mechanisms of compensation/decompensation and to specify the character of involvement of orbitofrontal cortex and hippocampus into these processes the spatiotemporal organization of brain electric activity was analyzed in 8 rats before and after electrolytic brainstem lesion at the level of the lateral vestibular nucleus Deiters (VND). The electric activity was recorded from symmetric frontal and somatosensory cortical areas, hippocampal areas CA1, and intact VND. Spectralcoherent analysis showed that adaptive reactions are most clearly manifested by changes in the spatiotemporal organization of the theata activity: 1) early brainstemhippocampal synchronization of the electric activity in the frequency range of 6-7 Hz with subsequent involvement of anterior cortical regions is characteristic of survived animals; 2) independent hippocampal-cortical hemispheric system of excitation in the frequency of 4-5 Hz precedes the fatal outcome. On the day before the fatal outcome the interhemispheric coherence in the orbitofrontal cortex dropped, which suggests the involvement of these brain regions into the processes of visceral regulation.

Long-term ongoing reorganizations of the processes of analysis of kinesthetic afferentation at the level of cat motor cortex neurons after damage to the ventrolateral nucleus of the thalamus.

The changes in the functional characteristics of neurons of field 4 of the motor cortex (MC) of cats before and at various times (from a week up to five months) following an ipsilateral lesion of the ventrolateral nucleus of the thalamus were investigated in semichronic experiments. The reactions of the cells to tactile stimulation of the forelimb and its passive movement at the wrist at an average speed of 170 degrees/sec were studied. It was demonstrated that a correlation between the impulse activity at speed maxima and the acceleration of monoarticular movement is characteristic for a number of cells of the MC of the intact brain. Experimental confirmation was obtained of the hypothesis, formulated on the basis of the results of preceding investigations, regarding a disturbance of the mechanism of detection by MC neurons of the kinematic indicators of movement following damage to the thalamus. It was established that compensation of this disturbance is associated with the facilitation of conduction to MC neurons of somatosensory afferentation. It is concluded that a morphofunctional reorganization of particular intracortical components of sensorimotor coupling underlies the mechanisms of the compensatory plasticity of the MC.

[Long-term rearrangements of the processing of kinesthetic afferentation at the neuronal level of the cat motor cortex after damage to the ventrolateral thalamic nucleus]. / Dlitel'no tekushchie perestroiki protsessov obrabotki kinesteticheskoi afferentatsii na urovne neironov motornoi kory koshek posle povrezhdeniia ventrolateral'nogo iadra talamusa.

Single-unit recordings from motor cortex (area 4) were obtained in cats and under semichronic experimental conditions before and within various periods (from a week to five months) after the lesion in thalamic nucleus ventralis lateralis (n. VL). Neuronal responses to tactile stimulation of the contralateral forelimb and its passive movement in the wrist joint with the mean speed 170 degrees/s were studied. As it had been already reported by others, the magnitude and time course of averaged response histograms for some neurons, which were evoked by imposed displacements of the forelimb, were related to the velocity and/or acceleration components of the movements. Spontaneous firing and kinematic processing capabilities of motor cortical cells were affected by the lesion. The findings are in agreement with a hypothesis that n. VL is essential for encoding specific kinematic features of angular joint movements. Restoration of kinematic processing by cortical neurons in the course of post-traumatic period was characterized by facilitation of activatory reactions of the area 4 cortical cells to peripheral cutaneous stimulation. Some suggestions are made on the nature of plastic changes which develop in neuronal nets of the motor cortex after the lesion of n. VL.

Change in neuronal excitability in hippocampal sections of rats isolated after the destruction of the medial septal area.

The influence of chronic destruction of the medial septal area (MSA) on focal potentials (FP) of field CA1 evoked by stimulation of Schaffer collaterals was studied in experiments on viable sections of the hippocampus of rats. The preparation, incubation, and pickup of FP of the sections of the control and experimental groups were carried out in identical conditions using traditional methods. The amplitude-temporal of population EPSP and population spikes, their interdependence, and their dependence on the strength of the stimulating current were assessed using automated data analysis. It was demonstrated that coagulation of the MSA is accompanied by an increase in the excitability of neuronal complexes of the lateral portion of field CA1 which is manifested by the generation of multiple rhythmic discharges and the development of spike activity of the cells at a lower intensity of the synaptic inflow. It is hypothesized that destruction of the MSA leads to a relative attenuation of inhibitory control in the neuronal systems of field CA1, the elements of which are depolarized with anomalous synchronicity and generate rhythmic impulse trains.

[Compensatory processes in the motor cortex of the cerebral hemispheres in partial damage to the ventrolateral thalamic nucleus in the cat]. / Kompensatornye protessy v motornoi kore polusharii mozga pri chastichnom povrezhdenii ventrolateral'nogo talamicheskogo iadra u koshki.

In cats alimentary instrumental reflex was elaborated of lever transference by the right forepaw in a definite zone--prior to and after the electrolytic damage of the left ventrolateral thalamic nucleus. It was found that even a slight damage led to disturbance of precise movements mostly expressed in the first two weeks; after that gradual normalization of the motor reactions took place. At morphological study of various pyramidal neurones and also satellite and general glia in the zone of presentation of the ventrolateral nucleus in the cerebral cortex a hypertrophy was discovered of the pyramidal cells and their processes in III and V layers, accompanied by active reaction of various glia forms. Morphometric processing and statistic analysis of the obtained data showed the dominance of structural compensatory changes observed in the cortex on the side of VL damage.

Kinematic analysis of the formation of precise instrumental movements in cats.

The kinematic parameters of the manipulatory motor reactions in the dynamics of the formation and consolidation of a precision skill consisting in the displacement and subsequent holding of a lever in a zone of "work" space signalized by a sound were studied in experiments on cats. It was established that the development of the skill passes through a stage of disinhibition of slow movements with a prolonged increase, prior to the appearance of the sound signal, in velocity. The skill which is consolidated in the course of subsequent training sessions is accomplished by uniform movements of the ballistic type, and is characterized by independance from the acoustic indication of the final position. At the same time, the relationship of the duration of the increase in acceleration to the beginning of the inhibition of the movement becomes an invariant parameter of the central program of the precision reactions.

[Epileptiform activity in the rat hippocampal slices isolated after local lesion of the septum by ibotenic acid]. / Epileptiformnaia aktivnost' v srezakh gippokampa krys, izolirovannykh posle lokal'nogo povrezhdeniia septuma ibotenovoi kislotoi.

Extra- and intracellular responses were recorded in the CA3 region of hippocampal slices of rats 1-4 weeks after intraseptal injection of ibotenic acid. Then they were compared with those from unoperated controls. In the slices from operated animals spontaneous and evoked synchronous epileptic field discharges were preserved invariably associated with paroxysmal depolarization shifts (PDSs) and bursts of action potentials of the cells. Both the field discharges and PDSs in the CA3 had an "all-or-nothing" character. There were no consistent effects of septal lesion on the mean resting potential or input resistance of the CA3 pyramidal neurons. Histological examination revealed a cell loss in the dorsal septum, whereas cholinergic neurons of the medial septum were not significantly damaged. The results suggest that intrinsic septal circuitry is critically involved in synchronization of CA3 neurons and control of their excitability.

[Changes in the neuronal excitability of rat hippocampal slices isolated after destruction of the medial septal area]. / Izmenenie neironnoi vozbudimosti v srezakh gippokampa krysy, izolirovannykh posle razrusheniia medial'noi septal'noi oblasti.

To determine if electrophysiological properties of hippocampal pathways are altered after medial septal area (MSA) destruction, extracellular recordings were made from hippocampal slices of rats 30 days following lesion and compared with those from unoperated controls. The preparation of slices, data accumulation and data analyses were done under the same conditions. The electrophysiological parameters of interest were the population spike (PS) and the field EPSP, produced in the CA1 pyramidal layer by stimulation of the Schaffer collaterals. The principal finding of this study was that neuronal excitability in slices from MSA-lesioned rats was altered. The most striking abnormalities were an epileptiform activity, which consisted of multiple PSs, and multiple seizure-like after discharges with a delayed onset to low stimulation intensities. In the CA1 region of the slices collected from lesioned rats the input-output curve of field EPSP versus PS showed a leftward shift as compared with their counterparts in normal slices. These changes may be related to relative reduction of inhibitory processes in interneuronal circuits of CA1 region.

[A kinematic analysis of the formation of precise instrumental movements in cats]. / Kinematicheskii analiz formirovaniia tochnostnykh instrumental'nykh dvizhenii u koshek.

Kinematic parameters of cats local manipulating movements have been studied in the process of formation and stabilization of precise habit of moving and holding the lever in the zone of "working" space signalled by sound. It is shown that change of activity of the motor control system in the course of training is connected with the transfer from current correction of performed reaction to optimization of controlled parameters of pre-paired movements. It has been established that the formed precise coordination is realized owing to rapid movements with monomodal asymmetric profile of speed. During habit stabilization time to peak velocity significantly dropped from 274.6 +/- 84.7 to 211.0 +/- 22.9 ms and its value increased from 119.5 +/- 27.8 to 182.2 +/- 44.4 degrees/s. The stabilized habit is provided by uniform movements of ballistic type and characterized by independence from sound indication of final position, its reaching time becoming a function of amplitude-temporal values of speed maximum. It has been found that in the process of motor learning the relation of the duration of acceleration growth to the beginning of movement inhibition becomes an invariant parameter of the central program of precise reactions.

[Electrophysiological analysis of septum-amygdala interaction at the level of the dorsomedial thalamic nucleus in the rat]. / Elecktrofiziologicheskii analiz septo-amigdaliarnogo vzaimodeistviia na urovne dorzomedial'nogo iadra talamusa krysy.

The characteristics were studied of focal potentials and impulse activity of 102 neurones of the thalamus dorsomedial nucleus (DMN) of anaesthetized rats under stimulation of the anterior periamygdalar cortex (APC) and septal lateral nucleus (SLN). The dominating type of impulse responses to APC and SLN stimulation recorded correspondingly in 31.4 and 12.8% of cells was expressed in a short latency (10-30 ms) phasic activation. It has been found that the convergence of these inputs, revealed in 9.8% of cells, is unidirected according to the genotype of the reaction. Neuronal complexes of DMN, organizing the responses to the stimulation of APC and SLN are characterized by a weak interaction testifying to a definite functional differentiation of the amygdalar and septal components of the lymbic-thalamic projection system.

[Neuronal correlates of the functional reorganization of the dorsomedial thalamic nucleus in the rat after damage to the amygdala]. / Neironnye korreliaty funktsional'noi reorganizatsii dorsomedial'nogo iadra talamusa krysy posle povrezhdeniia amigdaly.

Activity of the thalamic dorso-medial nucleus (DMN) cells evoked by stimulation of the periamygdaloid cortex was recorded in anesthetized rats in various periods of time after the baso-lateral amygdala destruction. It was found that changes in functional characteristics of cells observed at the early postoperative period intensified and reached the highest expression 10-30 days after such a destruction. Both the number of responding cells and percentage rate of neurons with excitatory and inhibitory responses restored along with the prolongation of the postoperative period. The structure of evoked excitation differed from the normal in predominant long-lasting tonic activation. Some peculiar features of functional reorganization of the DMN neuronal network involved in processing of incoming afferentation are discussed.

[Electrophysiologic and behavioral changes after destruction of the basolateral nucleus of the amygdala in the rat]. / Elektrofiziologicheskie i povedencheskie izmeneniia posle razrusheniia bazolateral'nogo iadra mindaliny u krys.

In experiments on rats the influence was studied of unilateral destruction of the basolateral amygdala on heterogeneous conditioned reflexes and focal potentials (FPs) of the dorso-medial thalamic nucleus, elicited by stimulation of the peri-amygdalar cortex. It is shown that reduction during 3-4 postsurgery weeks of the number of goal-directed reactions and increase of their latencies are accompanied by suppression of the evoked activity, testifying to disturbance of functional interaction between the structures of limbic and thalamic levels. Changes of FPs parameters, reflecting the establishment of new functional interrelations between the centres of the lesioned system excelled in duration compensatory restoration of properties of conditioned reflexes.

[Dynamics of recovery of evoked responses of the dorsomedial nucleus of the thalamus of the rat after injuries to the amygdala]. / Dinamika vosstanovleniia vyzvannykh otvetov dorsomedial'nogo iadra talamusa krysy posle povrezhdeniia amigdaly.

Time course of reorganization of patterns of the thalamic dorso-medial nucleus (DMN) focal potentials evoked by periamygdaloid cortex (PC) stimulation before and 2-90 days after the baso-lateral amygdala destruction was studied in semichronic experiments on anesthetized rats. The comparison of amplitudes and latencies to peaks of potential components as well as the analysis of their depth profiles were performed. Different stages of functional reorganization of the relationships between PC and DMN were observed. Latencies to peaks of the major positive-negative component increased within 2 months. Restoration of the potential pattern was found 2.5 months after amygdala destruction. But destruction of the amygdala markedly altered the recovery cycle of the focal potential to testing PC stimulation, especially when the interval between paired shocks was 40-150 ms. The results demonstrate a high degree of functional plasticity of the neural DMN connections which are needed to produce the focal potential after PC stimulation.

[Reorganization of the evoked neuronal activity of the dorsomedial nucleus of the thalamus in the rat shortly after destruction of the basolateral nuclei of the amygdala]. / Perestroika vyzvannoi neironnoi aktivnosti dorsomedial'nogo iadra talamusa krysy v rannie sroki posle razrusheniia bazolateral'nykh iader amigdaly.

Characteristics of the thalamic dorso-medial nucleus neuronal responses evoked by stimulation of the periamygdaloid cortex before and after the baso-lateral amygdala destruction were compared in anesthetized rats. Appearance of a new reaction in the form of a long rhythmic bursts and reliable decrease of phasic-active units and increase in the number of cells with tonic activation were found after such destruction. The number of units with spontaneous discharge increased without affecting the spontaneous discharge frequency. The mean duration of the tonic discharge increased from 142.5 +/- 42.4 ms to 375.4 +/- 53.8 ms but other parameters of the neuronal reactions did not differ significantly.