Changes in the electrical activity of the hippocampus during elaboration of an inhibitory reaction in the dog

A conditioned alimentary instrumental reflex was elaborated in three dogs with chronically implanted electrodes to a consecutive complex conditioned stimulus consisting of two equal acoustic stimuli separated by a pause. At first, the animals reacted with motor reactions during the whole action of the complex signal. Then inhibition of reaction was elaborated at first in pause and then in response to the preparatory stimulus. In the process of stabilization of inhibition, there was an increase of similarity of spectral composition of hippocampal theta-rhythm with the values obtained in the inter-signal period. Conclusion is made that the hippocampus is not a structure necessary for the elaboration of internal inhibition. The frequency of hippocampal theta-rhythm may serve as a characteristic of the property called in Pavlov's school mobility of the nervous system.     

Dissociation of reproduction of conditioned vegetative and motor reactions during retrograde electroconvulsive amnesia]

It has been shown in chronic experiments on rats that electro-convulsive action applied in five to ten seconds after one-session conditioning completely precludes the reproduction of conditioned motor reactions, while conditioned bradycardiac reactions are clearly reproduced in tests one hour and 24 hours after elaboration. Unconditioned stimulus presented in another experimental situation six to seven days after elaboration and amnesic action, leads to a stable reproduction of the previously non-achieved conditioned motor reactions. The results obtained suggest that electrical seizures influence the reproduction of motor reactions, rather than fixation of temporary connection.     

Reproduction of the electrophysiologic correlates of a conditioned defense reflex following electroconvulsive activity]

Acute and chronic experiments on cats have shown the possibility of obtaining in one session conditioned EEG-responses and vegetative changes as well as conditioned motor reactions time-locked to the moment of the unconditioned pain stimulation omitted during testing. Electro-convulsive stimulation directly after elaboration prevents the appearance of conditioned motor reactions, while conditioned EEG and vegetative changes are retained after electric seizures. A conclusion has been drawn that the emotional component of conditioned reactions is not subjected to the amnestic effect of electro-convulsive action.     

Conditioned reactions to time of hypothalamic neurons. The perifornical nucleus]

In 40% of the 52 neurones of the hypothalamic perifornical nucleus in alert rabbits conditioned trace reactions of the activational (52%) and inhibitory (48%) type were recorded in the course of elaboration of a conditioned motor reflex to time. The sign and pattern of the trace responses were determined by the nature of cell reactions to actual paired stimuli. After 50 to 70 pairings, the unit trace conditioned reaction to time persisted for a period of 10 to 15 successive omissions. Trace responses were observed most frequently in the 5th of 8th omissions. In some cases conditioned enhancement of cell activity coincided with the conditioned motor response to time. This fact together with the maximal development of a summery trace cellular response at the moment of formation of conditioned motor reactions attests the participation of neurones of the perifornical nucleus in maintaining conditioned motor activity.     

The dependence of the neuronal reactions of the sensorimotor cortex to a simultaneous complex stimulus on the level of the differentiation of its components]

On alert animals the change was studied of the neuronal activity of the sensorimotor cortical area of cats brain in dependence on the level of differentiation of the components of simultaneous heteromodal complex stimulus. According to the character of this dependence and a number of other parameters two groups of neurones were singled out in the sensorimotor cortex. It was shown that parameters of reactions of all recorded neurones of the sensorimotor cortex to the positive conditioned signal were the first established after consolidation of the animal conditioned motor activity. In the course of elaboration following parameters changed: expressiveness, intensity, duration and value of latency. Reactions of neurones of both groups to the inhibitory stimuli were stabilized only after consolidation of the habit of differentiation. Responses of the first group neurones changed only by the pattern of discharge, while the responses of the second group neurones could change by expressiveness of response, its sign, duration and value of latency. Oscillations of the differentiation level after finishing of the elaboration of inhibitory conditioned reactions affected only the responses of the second group neurones to complex components.     

Effect of cadmium chloride on the processes of learning and memory in rats

Intraperitoneal injection of cadmium chloride (4 mg/kg) to rats before elaboration or reproduction of two-way avoidance conditioned reflex (TACR) disturbs both these processes. Deterioration of elaboration does not affect connections fixation and their subsequent reproduction. Injection of the substance before the elaboration of passive avoidance conditioned reflex (PACR) depresses elaboration and consolidation. Injection of cadmium chloride before testing of PACR preservation does not influence the processes of engrams reproduction. The observed disturbances cannot be connected with changes of animals motor activity.     

Characteristics of cortical responses to electrostimulation of the internal geniculate body during formation of a defensive conditioned reflex]

During elaboration of a classical defensive conditioned reflex the dogs exhibited a dependence of the changes in amplitude and configuration of evoked potentials (EP) to electrical stimulation of the medial geniculate body (MGB), a conditioned stimulus, on the nature of effector manifestation of the conditioned reflex: the late components were the most depressed at multiple phasic reactions and not infrequently increased and became complicated at single and short motor reactions as well as at their incidental absence. The primary oscillations, while mostly remaining unchanged, were depressed in the case of conditioned reactions attended with a general motor restlessness. A difference has been revealed during conditioning in the EP changes to electrical stimulation of MGB and to an adequate peripheral stimulation. It has been assumed that EP changes during conditioned activity are determined by the relationship between the levels of tonic and phasic cortical activation.     

Effect of fenamin and haloperidol on conditioned activity of neurons of the motor cortex and striopallidal system

The activity of neurones in the motor cortex, caudate nucleus, putamen and globus pallidus was studied during elaboration of motor conditioned reflexes to time in rabbits, treated with 1-amphetamine and haloperidol. Mechanisms of reproduction of cells trace activity in the reflex to time at the omission of trials, reacted to 1-amphetamine by increasing the intensity of reactions in the motor cortex and inactivation in putamen cells. The curve of dynamics of intensity changes of trace discharges in the course of a series of trials omissions remained unaltered only in motor cortex; in the other structures it significantly differed from the norm of intact animals. Haloperidol depressed the mechanisms of reproduction of trace reactions of the globus pallidus cells, and made them almost fully inactive in the motor cortex; the putamen neurones reacted to haloperidol by an increase of trace reactions intensity. Against the background of the animal chronic 1-amphetamine intoxication, haloperidol normalized the dynamics and intensity of trace activity. "Therapeutic" effect of haloperidol was most distinctly expressed in the motor cortex and putamen cells, less--in the caudate nucleus and was completely absent in the globus pallidus.     

Dynamics of elaboration of a conditioned reflex and differentiations in the snail

It is shown that dynamics of percentage of conditioned food refusals by snails Helix pomatia and Helix lucorum is satisfactorily approximated by regression equation of exponential type with included coefficient reflecting the animals state before the beginning of learning. The ability is established of the snails to practically completely differentiate various alimentary conditioned stimuli. The introduction of differentiation always improved the reflex consolidation. Conditioned reactions to differentiation stimulus appeared at the elaboration stage and were absent at the stage of conditioned reflex consolidation.     

Disruption of situational reflexes in experimental neurosis brought on by changes in the space factor

Motor activity elaborated in dogs and consisting of delayed choice reactions in a stochastic system (methods developed by Beritashvili, Hunter) and of rhythmic stereotypes of motor situational reflexes (Kupalov method) was not impaired by changes in spatial parameters of unconditioned stimulus in the stochastic system of choosing one feeding trough out of five. The changes in the spatial arrangement of conditioned and unconditioned stimuli in stable stereotypes led to changes in the behaviour of the animals and experimental neurosis with long-lasting disturbances in the situational conditioned reflexes and the short-term memory.     

Conditioned reactions of hippocampal neurons during amphetamine poisoning and its counteraction with haloperidol

Activity of 144 neurones of the dorsal part of the rabbits hippocamp was recorded during elaboration of motor conditioned reflex to time. Chronic amphetamine intoxication lowered the ability of hippocampal neurones to form conditioned reactions in response to pairings of sound stimuli with electrocutaneous reinforcement and fully suppressed mechanisms of reproduction by cells of engrams of previous pairings in series of their omissions Single administration of haloperidol to intact animals somewhat increased the number of neurones reacting to the pairing and their omissions in conditioned reflex to time without significantly influencing the intensity and dynamics of reproduction of endogenous cellular reactions in the series of consecutive omissions of pairing. Haloperidol administration during amphetamine intoxication elicited shifts towards normalization of conditioned activity of neurones, eliminating the suppressing action of amphetamine on mechanisms of reproduction of engrams of combined stimuli. Such "therapeutic" effect of haloperidol in many cases did not depend on the character of its psychotropic action. The properties of amphetamine and haloperidol action on the cells of the hippocamp are discussed as compared to their action on the neurones of other brain structures, previously studied in an analogous experimental situation.     

The role of the lateral and medial hypothalamus in reproducing a motor reaction as the signal during the acquisition of classical conditioned reflexes]

In experiments on three dogs there was shown that testing electrostimulation of the lateral hypothalamus reproduced the motor reaction which is a signal stimulus at elaboration of classic alimentary conditioned reflexes (CRs) and did not reproduce it at elaboration of classic defensive CR. Testing electrostimulation of medial parts of the hypothalamus reproduced, as LH electrostimulation the "signal" motor reaction, but in less percentage of cases, during elaboration of classic alimentary CRs and did not reproduce it at elaboration of classic defensive CRs. The reproduction of the signal motor reaction at LH electrostimulation is connected with activation of backward conditioned connection from motivation structures of the hypothalamus to representation of the signal stimulus in the motor cortex.     

Effect of electric stimulation of the somatosensory cortex and caudate nucleus on extinctive inhibition of a conditioned alimentary reflex to sound]

In experiments performed on 9 dogs with alimentary method, extinctive inhibition was deepened and its elaboration was aceelerated by electrical stimulation of somatosensory and motor cortical areas and ventral segment of the caudate nucleus head. The extinction of the conditioned reflex was slowed down by stimulation of the anterolateral gyrus and the central segment of the caudate nucleus head. General motor excitation of animals during stimulation of the dorsal zone of caudate nucleus head impaired the elaboration of extinctive inhibition.     

A comparative neuropsychological approach to the analysis of hippocampal functions

Formation of conditioned switching-over of heterogeneous instrumental reflexes in dogs was more successful than in rats, which testifies about significant differences of the functional organization of analytical-synthetic brain activity in rodents and predatory animals. Experiments with lesion of the hippocampus (in rats) and the records of its electrical activity (in dogs) allowed to conclude that the hippocampus of the both types of animals belongs to the system of structures, participating in the formation of conditioned switching-over. The data, obtained in the process of elaboration of the switching-over and probabilistic reinforcement of the alimentary conditioned stimulus, testify that providing for the reactions to signals with low probability of reinforcement in different species of animals is one of the functions of the hippocampus.     

The long-term effect of acute hypoxic hypoxia on shuttlebox avoidance learning in rats

Long-term influence was studied of the acute hypoxic hypoxia seance on rats behaviour in situation of elaboration of the conditioned reaction of active avoidance of electric shocks in shuttle chamber. It was found that in 2.5-3 months after the hypoxia seance, the experimental animals significantly differed from the intact controls by dynamics of CR elaboration (rats which had hypoxia were ahead of the control ones) and by distribution of the conditioned reactions latencies (for experimental animals this distribution was shifted to minor values). The character of these behavioural shifts coincided with that observed in the group of rats with local unilateral hippocampus lesion. The obtained results and numerous data presented in literature on the influence of the hippocampus lesion on animals shuttle avoidance learning, allow to conclude that the seance of hypoxic hypoxia leads to the disturbance of the hippocampus function. This conclusion conforms to the data on diffusive death of the hippocampal and neocortical neurones as a result of hypoxia action.     

Spatial characteristics and the dynamics of the activation foci in the cortex during the elaboration of a conditioned reflex (thermographic research)

In acute experiments on immobilized white rats, by thermovision methods and digital image processing, spatial distribution and dynamics of local heating and cooling of dorsal surface of the cerebral cortex was studied through intact skull during elaboration of a conditioned reflex. Distant and noninvasive thermovision methods allowed to reveal and quantitatively study local cortical thermal reactions in the somatosensory and motor cortex and in the cerebellum in the process of elaboration and testing of conditioned connection. Under discussion are mechanisms, properties and significance of these effects for investigation of learning.     

Features of the formation of conditioned secretory reflexes in response to the stimulation of different areas of the caudate nucleus of the dog

Properties were studied of elaboration of conditioned alimentary secretory reflexes to threshold electric stimulation of the caudate nucleus in dogs. The rate of formation of such a reflex and its magnitude were considerably lower than in reflexes elaborated to distant stimuli. Latencies were longer; dynamics of conditioned and unconditioned secretory reactions was similar to that of reflexes to a weak stimulus--light. The motor component of the conditioned alimentary reaction, as a rule, was absent. Characteristics were revealed of formation of alimentary reflexes to stimulation of the dorsal and ventral parts of the head and body of the caudate nucleus.     

Effect of vasopressin on changes in the behavioral reactions of rats induced by psychotropic substances

The effect was studied of arginyl-8-vasopressin (AVP) on changes in rats behavioural reactions, elicited by reserpine, haloperidol, aminazine, amitriptyline or nialamide. It has been shown that AVP administered intraperitoneally in a dose of 0.001 mg/kg, eliminates the deficit of elaboration of conditioned reaction of active avoidance produced by psychotropic drugs, without influencing the motor activity reduction developed after administration of these substances.     

Recovery of instrumental conditioned reflexes in rats after pyramidotomy and action of bacterial melanin

Unilateral pyramidotomy at the bulbar level performed after preliminary elaboration of instrumental conditioned reflex (ICR) and without its elaboration caused hemiparesis of extremities in rats. Next day after this operation a half of the operated animals both with elaborated ICE and without its elaboration was injected intramuscularly with bacterial melanin solution (170 mg/kg). Comparison of terms of recovery of ICR and of a balancing movement of the paralyzed hindlimb in the operated rats without administration of melanin and with its injection showed that in the “melanin” animals the time of posttraumatic rehabilitation was much shorter and recovery of movement occurred faster and more completely. It has been found that the difference in terms of recovery of rat motor functions in this case is due to the protective action of bacterial melanin.     

Correlations among cortical potentials in the dog during the elaboration of motor alimentary conditioned reflexes

Background electrocortical activity in a frequency band of 1-100 Hz of dogs with electrodes implanted in different neocortical areas was studied before and after elaboration of motor (lever pressing) alimentary conditioned responses. Conditioning led to a significant change of the distribution histograms of cross-correlation coefficients (CC) between the cortical potentials, i. e. the dispersion of CC values decreased and the level of correlation changed as well. In more tranquil animals (with lower CC values before conditioning) the level of correlation significantly increased, in excitable ones (with higher CC values before conditioning) it decreased. CC distributions after the conditioned response elaboration became similar in both cases apparently indicating the formation of a uniform state characteristic for the type of a conditioned response under study.