[Features of the spatial organization of EEG manifestations in different variants of anxiety symptoms in patients with depression]

Investigations were carried out on 36 patients with reactive depressive states and repeating depressive episodes with severe manifestation of anxiety syndrome. The spatial organization of brain activity by cross-correlation analysis was studied. Shown, that clinical depression and anxiety syndrome is reflected in the structure of the spatial organization of EEG depending on options manifestation of anxiety disorder.

[Features of the organization of biopotentials of a cerebral cortex and visceral status at the person at neurotic depression]

Researches are spent on 20 patients with various clinical variants of neurotic depression. The regional organization of bioelectric activity of a brain by a method cross-correlation and coherent analysises was studied. Vegetovisceral status was studied by auricular criotest (measuring of cold sensibility of auricular points). It is shown, that the clinical picture of neurotic depression finds reflectance in frame of regional organization EEG. Regional organization EEG is modified depending on a degree of manifestation of the most neurotic depression and concomitant syndromes of alarm and an asthenia. In bunch with a depressive syndrome without concomitant asthenic and disturbing exhibitings the maximum changes are taped in the right frontotemporal range--left posttemporal ranges. In bunch where along with depression the alarm--depression cross-correlation and coherent communications frontotemporal ranges of both hemispheres was taped, strongly pronounced rising cross-correlation attitudes in right occipital ranges. In bunch where depressive and disturbing syndromes were combined with the expressed asthenic exhibitings, depression cross-correlation and coherent communications in frontotemporal ranges of both hemispheres was observed. The clinic of neurotic infringements finds reflection in a specific picture of variations of the spatial organization of electric activity of a brain and in variations of parameters of the vegetovisceral status. Realization of negative emotional conditions at the person is accompanied by variations visceral functions. Thus variations in the central brain structures cover zones of representation of emotional reactions and the zones connected with cortical representation visceral functions. The minimal central regulation, even insignificant central variations can cause vegetovisceral dysfunctions.

[Modification of evoked potentials by increasing visual search difficulty in humans]

Monopolar evoked potentials on increasing difficulty of the task of visual search in frontal, parietal, temporal and occipital regions was studied in 16 young healthy subjects. Search complication and adding noise in the form of visual stimulus hindered recognition of images that affected search time and errors amount. Correlation between evoked potential magnitude and parameters of the search generally observed in frontal region: a significant positive one between N2, P4 components; between SN-SP difference waves and task difficulty: a negative one between P3 and N2 components. Amplitudes of N2 and P4 components were mostly expressed in frontal lobe. It was supposed that the data obtained indicated dominance of the frontal structures in the attention system during increasing the difficulty of the task.

[On using EEG autointerval-grams for analysing reactions to periodical light stimulation]

We have analyzed autointerval-grams of the extremums of human electroencephalograms, registered during periodical light stimulation. We have compared them with the visual analysis of EEG and EEG's testing by sinusoids. We have shown that in most cases building interval-grams is as good or even better than two other methods, as it allows us to discover reactions and obtain additional information.

[Characteristics of the EEG spatial organization of the brain neocortex biopotentials in various clinical neurotic depression]

In 20 patients with various clinical variants of neurotic depression, regional organization of the brain bioelectric activity was studied with the aid of cross-correlation, factorial and coherent analyses. Clinical picture of neurotic depression was reflected within the frame of regional organization of the EEG. Regional organization EEG is modified depending on the degree of neurotic depression manifestation and concomitant syndromes of alarm and asthenia. In depressive syndrome without concomitant asthenic and disturbing, the maximum changes are registered in the right fronto-temporal range--left post-temporal areas. In depression and the alarm, depression cross-correlation and coherent communications in fronto-temporal areas of both hemispheres were recorded. In depressive and disturbing syndromes with the asthenic manifestations, depression cross-correlation and coherent communications in fronto-temporal areas of both hemispheres were observed.

Characteristics of activation in the parietal areas of the cortex in humans in different types of visual attention

The state of cortical activation in the parietal and temporal areas was assessed using evoked potentials (EP) during the tasks of selection of lateralized visual stimuli requiring three different types of attention: to stimulus shape, to stimulus position, and to both. Studies in 15 young, healthy subjects involved recording of EP in six cortical leads: P3, P4, T3, T4, T5, and T6, with analysis of the endogenous EP components CNV, N1, P3, and the EP complex [N1-P3] (according to standard terminology). Changes in EP components in response to the attended and non-attended stimulus features were compared. Differences between them were assessed using the index of selectivity of attention to one or another feature of the visual stimuli. In the parietal area, selectivity was seen in conditions of attention to stimulus position and attention to stimulus shape. In conditions of simultaneous attention, the indexes of selectivity were essentially equal to the sum of the indexes of selectivity of attention to shape and position. The most marked endogenous EP components (CNV, N1, and P3) in visual selection were seen in the parietal areas, with a greater gradient of increased activation of the parietal areas of the cortex as the need for attention increased, along with a lower threshold for the action of attention, and anticipatory development of the P3 wave in the parietal area as compared with the temporal area. These results suggest that the parietal cortex has priority in the visual attention system and that the magnocellular (M) pathway forms the most important visual input to the dorsal parietal area of the neocortex.

Cross-interval histograms for analysis of brain electrical activity

A method for constructing cross-interval histograms for time-localized EEG fragments of particular types is described. The basic principles of the method are presented. Examples of cross-interval histograms constructed for EEG extrema and their derivatives are presented. Cross-interval histograms were shown to include peaks, troughs, and other features. Cross-interval histogram and cross-correlation histograms are compared. The method yields qualitatively new data on interactions between changes in biopotentials in different areas of the brain and allows rapid processes to be studied.

[Interhemisphere differences of extrastriate cortical activation during attention and selection of lateralized visual stimuli in humans]

The cortical activation was estimated by event-related potentials (ERPs) methods during selection tasks of lateralized visual stimuli in right and left hemi-fields requiring different forms of attention: 1. Attention of a stimuli form, 2. Attention of a stimuli position, 3. Combined attention of form and position. ERPs were recorded in 15 young healthy adults in 6 leads: P3, P4, T3, T4, T5, T6 and endogenous ERPs components: CNV (contingent negative variation), N1, P3 and complex [N1--P3]. The differences between ERPs at contra- and ipsilateral stimuli in the right and left hemispheres were considered as indices of asymmetry. The asymmetry was revealed in right hemisphere in all kinds of attention forms. The level (amplitude) of right-side asymmetry was depended on the level of attention: The significant relation between the right-side asymmetry and subjects' reaction time was also revealed. It is proposed that such an asymmetry is the evidence of better spatial differentiation of visual stimuli in right hemisphere in humans.

[Characteristics of the parietal cortex activation in humans during different attention tasks]

The cortical activation was estimated by the event-related potential (ERPs) methods during selection tasks of lateralized visual stimuli requiring different forms of attention: 1) form of stimuli, 2) stimuli position, 3) combined attention of form and position. The ERPs were recorded in 15 young healthy adults in 6 leads P3, P4, T3, T4, T5, T6, and endogenous ERPs components: CNV (contingent negative variation), N1, P3 and the complex [N1-P3]. Differences between the ERPs at "attended" and "non-attended" stimuli were considered as indices of selection attention of particular feature of visual stimuli. Such indices of form and position were revealed selectivity in parietal leads. The most eminent ERPs components, the pronounced activation gradient during increase of attention demands were revealed in parietal regions (vs. temporal ones). In our opinion, parietal cortex has a high priority in selection attention system.

[Crossintervalograms for analysis of electrical activity of the brain]

A method of construction of crossintervalograms for electroencephalograms is proposed. Particular points or EEG fragments of particular shape are used as time-locked events, and the intervals between these reference points are analyzed. The method is theoretically substantiated. Examples of crossintervalograms constructed for EEG extrema and derivative EEGextrema are given. The information validity of these crossintervalograms is demonstrated and their features are indicated. Comparison crossintervalograms with crosscorrelograms is performed. The possibilities of further development and applications of a method are specified. It is suggested that the method will be useful for investigation of operative interaction of brain subsystems.

Effects of selective visual attention in the parietal and temporal areas of the human cortex using evoked potential data

Studies of 11 young subjects addressed the analysis of evoked potentials in the parietal and temporal areas to sequential presentation of visual symbols on the left and right sides; symbols were squares and circles and were observed passively and in conditions of selective attention to target stimuli presented to the subjects in random order and requiring rapid and precise motor responses. Comparison of monopolar evoked potentials in leads P3, P4, T3, T4, T5, and T6 with bipolar potentials in leads P3-T3, P3-T5, P4-T4, and P4-T6 in conditions of passive and selective attention showed that voluntary attention was accompanied by significant rearrangements in evoked activity in the parietal and temporal areas. This was evident as: 1) an increase in correlations between evoked potentials in the parietal and temporal areas; 2) stabilization of monopolar evoked potentials over time, i.e., increases in the correlations of sequential evoked potentials, in both associative visual areas; 3) stabilization of bipolar parietal-temporal evoked potentials in terms of increases in their sequential correlations. It is suggested that selective attention facilitates linked activity of the two associative areas, which is needed for performance of visual selection.

Genetic determination of neurophysiological mechanisms of cortical-subcortical integration of bioelectrical brain activity

The contribution of genetic factors to the formation of the neurophysiological mechanisms of cortical-subcortical integration was studied in 12 pairs of monozygotic and five pairs of dizygotic twins (aged 18-25 years). Intrapair similarity of the nature of spatial interactions between bioelectrical activity in the cerebral cortex, assessed from different combinations of statistical interactions of EEG from 16 monopolar recordings, was assessed in each pair of twins (and among 544 non-related pairs of subjects in both groups). The results suggest a high level of general population invariance and relatively small inherited and phenotypic variability in the morphofunctional systems making up the major neurophysiological mechanisms of brain integration as a whole. The ontogenetic formation of stem and subcortical regulatory structures, which have a leading role in the systems combination of different parts of the brain into a single formation, appears to occur in all individuals by the same principle, as disturbance can apparently affect the fundamental monomorphic features of the species. In turn, we might expect to find large interindividual variability in the establishment of interregional connections of the neocortex, the role of inherited and environmental factors being different in the processes forming long and relatively short intercortical interactions.

[Construction in chimpanzees]

Chimpanzees with the help of reconstruction and the "step-by-step" analysis of a figure--sample can plan a circuit of actions, forming an image of an end result. Ability to such actions proves at them an opportunity of cogitative operations, allowing to collect multielement figures on a sample. Generalization of concrete operations with concrete elements creates the precondition for the generalized understanding of a principle of actions--knowledge--in general to collect separate elements in complex designs. In it the powerful conceptual potential chimpanzees is covered. It allows to use chimpanzees as model preverbal a level of thinking.

[Manifestations of selective visual attention in human parietal and temporal cortex according to evoked potentials]

The event-related potentials (ERPs) in visual discrimination task in parietal and temporal cortical areas were recorded in 11 young adults during passive observation (involuntary attention) and target selection (voluntary attention). The voluntary selective attention resulted in: 1) increased ERP correlation between the parietal; and temporal cortical areas; 2) increased correlation of sequential ERPs in monopolar leads (P3, P4, T3, T4, T5, T6); and 3) increased correlation of sequential ERPs in bipolar leads (P3-T3, P3-T5, P4-T4, P4-T6). The findings suggest that voluntary attention maintains a concordant activity of the parietal and temporal cortical areas in execution of visual selection tasks.

Assessment of the state of activation of the cortical zones in humans during visual attention and selection

The state of cortical activation during visual symbol shape and position selection tasks was assessed in humans in terms of the magnitude of prestimulus negativity (contingent negative variation, CNV) and the amplitude of the N1-P3 complex in evoked potentials (EP). Evoked potentials in the frontal parietal, occipital, and temporal leads were recorded in 18 young healthy subjects in two sets of experimental conditions: in a screened chamber and in an "open field" beside the experimenter, who communicated the results to the subjects and guided them towards quicker and more precise responses to the target stimuli. The maximum magnitudes of CNV and evoked potentials during selective attention were seen in the parietal areas, and additional increases of activation indexes were observed in the "open field," where subjects' motivation was enhanced. The state of readiness (CNV) was an informative measure of cortical activation, as it determined the parameters of subsequent evoked potentials; the more marked the readiness, themore marked and stable were EP. Comparison of the situations of passive observation and selective reactions to stimuli revealed a reciprocal relationship between CNV in these conditions: the greater the magnitude of CNV in "passive" conditions, the smaller the difference between CNV in "passive" conditions and during selective attention and vice versa. We termed this "additivity of involuntary and voluntary attention." The fact that activation indexes were greatest in the parietal areas suggests that the occipital-parietal system is dominant in visual selection tasks in humans.

[Genetic determination of the neurophysiological mechanisms of the cortico-subcortical integration of bioelectrical activity of the brain]

Contribution of genetical factors to neurophysiological mechanisms of cortico-subcortical integration was investigated in 12 pairs of the monozygotic and 5 pairs of dizygotic twins (aged from 18 to 25). In each pair of twins as well as in all 544 unrelated pairs of subjects from both groups, interpairs similarity of the character of the spatial interaction of bioelectrical activity of the neocortex for different combinations of statistical correlations of EEG (from 16 monopolar electrodes) was estimated. The data obtained allow to suggest a higher common population invariance and a relatively small hereditary and phenotypic variability of morphofunctional systems, which underlie neurophysiological mechanisms of the brain integration in general. Apparently, the formation of the brain stem and subcortical regulatory structures in the ontogenesis, the structures that play the main role in the realization of system combination of different parts of the brain into united formation, occurs to all individuals according to a single principle since its disturbance can probably affect the fundamental monomorphal features of the species. In turn, one can expect a great interindividual variability of establishing of the intraregional connections of neocortex, the role of genetic and environmental factors in the formation of short and relatively long interactions being complex.

[Neurophysiological mechanisms of acquisition of fear-resistance habit controlled by biological feedback displayed by skin galvanic response]

The aim of the study was to reveal a probable structural-functional basis of emotional self-regulation processes within the framework of cortex--basal ganglia interaction using on-line computer analysis of the EEG. The tested subjects were unable to overcome the emotional stress increasing in the process of decision making under conditions of high responsibility for the results of task solving. Striving to hold their social positions these subjects created a stable psychological set to keep their high responsibility and resist the relaxation tendency. Such a set facilitated the acceptance of the task for volitional effort to resist fear controlled by a biofeedback displayed in skin galvanic reaction.

[Activation of the human cortex during visual attention and selection]

Cortical activation in visual discrimination tasks was estimated by measurement of the CNV (contingent negative variation) and N1-P3 components of visual ERPs in frontal, parietal, occipital and temporal leads recorded in 18 young healthy adults. In all investigated tasks, the maximal values of CNV and ERPa were observed in parietal regions. The estimation of cortical readiness state (CNV) is quite a useful procedure in the attention tasks because amplitude and stability of ERPs depend on preceding cortical excitability. The prevalence of parietal activation in visual attention tasks may be considered as the dominance of occipito-parietal way (stream) in human visual attention system.

[Basal ganglia and behavior]

A comparative analysis of the most well known hypotheses of basal ganglia participation in organisation and control of behavioural functions, is presented.

Functional rearrangements in the human brain during emotional self-regulation with biological feedback

The concept that functional psychopathology producing phobic syndromes is mediated by a specific deficiency in the integrative activity of the brain as a loss or partial limitation of the ability to recognize subjective experiences was used to develop a special method for mobilizing the selective attention of patients to the time course of subjective states. The fact of recognition of a state was demonstrated by the patient's ability to reproduce it by achieving specific parameters in a biological feedback test based on skin electrical responses. Success was positively reinforced by avoidance of an anxiously expected electrical stimulus. After successful training, patients could spontaneously adaptively correct their general daily behavior. Computer analysis of EEG traces revealed the specific structural-functional features of various states provoked during training.

Corticostriatal mechanisms of behavior

This article presents the results of three series of experiments on cats, dogs, and lower primates, performed to investigate the structural, neurophysiological, and mediator mechanisms of the corticostriatal systems involved in the organization of behavior. Morphological studies of corticostriatal connections showed that along with the diffuse distribution of afferent terminals within the striatum, there were also elements of topical organization defined by anteroposterior and mediolateral gradients. Neurophysiological experiments on dogs and lower primates were used to study the spike activity of the prefrontal region of the cortex and the head of the caudate nucleus during training to conditioned first- and second-order reflexes and during the solution of complex problems involving delayed spatial selection. Studies demonstrated that while in dogs, most of the neurons recorded showed a transition to responses to the conditioned signal at a particular stage of carrying out a conditioned response, in monkeys all cells recorded showed specific responses at different periods of solving the task at all stages of the study. Neuropharmacological experiments on dogs showed that agents blocking glutamine receptors in the caudate nucleus had more pronounced effects at the phase of developing conditioned movement reflexes. Administration of these agents during the reflex reinforcement phase affected only the differentiation of inhibition. These results lead to the conclusion that the prefrontal area of the cortex and, to some extent, the caudate nuclei, act on incoming information specifying the current dominant need and the states of the external and internal environments, to carry out programmed actions and assess the results of these actions.

Neurophysiological mechanisms of cortical-subcortical interactions in the organization of behavior

Experimental data are discussed within the framework of the fundamental areas of studies of the neurophysiological mechanisms of behavior. The first of these is the study of the activity of individual neurons, which is characterized by plastic rearrangements based on synaptic, molecular (neurochemical), and submolecular (genetic) processes. The second area is the study of the activity of neuron systems, which unite the cells of different microgroups, and of systems including neural elements of different brain structures. Data on plastic rearrangements of neuronal activity in different structures during different types of behavior lead to the conclusion that the brain has special systems of relationships which characterize the interactions of blocks of neurons, in which the plasticity of a single neuron can maintain the integration processes of the whole system. Our own data, along with results of Russian and foreign physiological and clinical investigations, suggest that neurons unite into different functional blocks at different phases of conditioned reflex behavior, thus determining the dominance status of different centers and the vector of a purposive behavioral act in a given situation at a given time. Possible directions for further basic studies of the interactions between innate and phylogenetically acquired functionally specific neuron units are discussed on the basis of hypotheses which have been advanced to explain the neurophysiological organizational mechanisms of higher brain functions.

Participation cholinergic systems of the dorsal and ventral striatum in the training of rats to avoidance in a T-maze

Influence of activation of cholinergic systems of the dorsal (Caudate- Putamen) and ventral (Accumbens) striatum on the process of the training of rats to active avoidance in a T-maze was investigated in experiments on 60 male Sprague-Dawley rats. The results, obtained on one and the same behavioral model (active avoidance in a T-maze), suggest the presence of particular features of the participation of the cholinergic systems of the dorsal and ventral striatum in the regulation of motor behavior. Thus, a one-time administration of carbacholine (Cbch, 0.03 microgram) increases the level of correct responses on the first and succeeding days of the training of the rats to active avoidance, when microinjections are made into the right Accumbens, and also induces a significant increase in the level of correct realizations on the second and third days of training when microinjections are made in the left Accumbens, and at the same time, similar influences on the Caudate-Putamen do not induce any significant changes in the behavior of the animals during training in a T-maze. The changes in the locomotor activity according to collective data in the various groups of rats exhibited a generally complex character from experiment to experiment, the level of the locomotor activity of the animals decreased in the majority of cases, but microinjections of the substances did not alter the locomotor activity of the animals in any of the groups. However, the degree of change in the level of locomotor activity in the group of rats with microinjections into the Accumbens (in this investigation, the degree of increase) very markedly depended on the localization of the cannula. The greatest effect was obtained in the lateral segment of this nucleus; this confirms the functional heterogeneity of this fairly small nuclear structure.

[Functional transformations of the human brain during emotional self-regulation with biofeedback]

By means of a special technique, mobilising of a subject's selective attention upon the dynamics of the subjective sphere states, was reached. An involved biofeedback was positively reinforced by avoidance of an expected electric stimulus. The subjects revealed occurrence of an adaptive correction of their general behaviour. The EEG computer analysis manifested a specifics of structural-functional maintenance of different states evoked in the training process.

[The corticostriatal mechanisms of behavior]

Experiments in dogs, cats and monkeys revealed that, along with the diffuse principle of afferent terminal arrangement within the striatum, there exist some features of terminal organisation by the anterior-posterior and medio-lateral gradients. The data obtained suggest that the prefrontal cortex and the caudate nucleus head maintain programming of intentions and the evaluation of performed actions.

[Neurophysiological mechanisms of the cortical-subcortical interrelationships in the organization of behavior]

Specific intersystem relationships seem to exist characterising interrelationships among neurons within pools of which plasticity of a single neuron is able to maintain integration processes of the whole system. The neurons under study seem to become united into various functional blocks during different phases of conditioned behaviour which determines a formation of a dominant condition of the centres and vectors of a specific behavioural action in a given situation and at a given time.

[The participation of the cholinergic systems of the dorsal and ventral striatum in the active avoidance learning of rats in a T maze]

Influence of cholinergic activation of dorsal (caudo-putamen) and ventral (accumbens) striatum on active avoidance learning was studied in chronic experiments in Sprague-Dawley male rats. The results obtained on the same behavioural model testify to specific roles of dorsal and ventral cholinergic systems in the control of motor behaviour. Single carbacholine microinjection into the right Accumbens increased the level of correct responses on the first and subsequent learning days. Similar microinjection into the left accumbens on the first training day improved the level of correct responses on the second and the third learning days. Microinjections into the dorsal striatum did not change active avoidance learning in T maze. Changes in locomotor activity of the animals of different experimental groups were principally of the same nature, i.e., the level of locomotor activity in the open field decreased from trial to trial in all the groups. Carbacholine microinjection did not change spontaneous locomotion in rats. However, there were variations in modifications of locomotor activity induced by microinjections into accumbens depending on localization of the cannula. Injection into the lateral accumbens induced the most pronounced changes. This fact testifies to the functional heterogeneity of this small nucleus.

Structure of neuronal activity of the caudate nucleus of monkeys during decision-making and the realization of the motor program in different variants of a delayed spatial choice task

In this paper the results of investigations of the participation of caudate nucleus neurons in the decision-making process and the process of organization of the program of a future motor response during the performance by Macaca mulatta monkeys of a delayed spatial choice tasks of varying degrees of complexity are presented. The presence in the caudate nucleus of spatially selective neurons, which are subdivided into two groups, was established: the position of conditional signals is reflected in the activity of one of the groups, and the direction of the future motor response is reflected in the activity of the other. The decision-making process is reflected in the impulse activity of neurons of the head of the caudate nucleus in two of its aspects: as the formation or choice of a specific motor program (spatially selective activity) and as a transitional factor from the instructive to the executive phase of the behavior.

[The structure of the neuronal activity of the caudate nucleus in monkeys making a decision and realizing the motor program in different variants of a task of delayed spatial choice]

Spatial-selective neurons were found in the monkey caudate nucleus, the neurons being divided into two groups: one of them reflects the location of conditioned signals, the other--the direction of future motor response. The decision-making process is reflected in the unit activity in two aspects: as formation or choice of a concrete motor program, and as a transitory moment from instructive to executive phase of the behaviour.

[The amygdala-caudate system and behavior]

Discussion of the cortical-subcortical interactions in organization of the behavioral reaction of various biological significance. Analysis of vast original experimental data on the morphology of the amygdala-caudate relations, on the neuron reconstructions in the cortical-subcortical systems under the positive and inhibitory conditioned reflexes, on the role of individual nuclei of the amygdaloid body in the trophic and defensive reactions, in organization of internal inhibition.

The participation of mediator and peptidergic systems of the brain in conditioned reflex mechanisms

New data on the significance of mediator and peptidergic systems of the striatal level in the organization of alimentary conditioned reflexes are presented in this report. The role of acetylcholine-, dopamine-, GABA-and P-ergic systems of the caudate nucleus and the amygdala in the realization of positive and negative conditioned reflexes was investigated. The experiments were carried out on dogs with chemotrodes and microelectrodes implanted in subcortical structures. The results of the experiments with microinjections of the relevant substances into individual subcortical structures showed that activation of the same mediator system in various structures may lead to both unidirectional and multidirectional behavioral effects. On the other hand, the activation of various subcortical mediator systems can lead to identical changes in conditioned reflex activity. The effect of the administration of activators or blockers of a subcortical mediator system depends in many ways on the functional state of the nervous system at the moment of administration and on the localization of the microinjection. It is difficult to predict beforehand the role of various subcortical structures in the organization of integrated behavioral acts. The question of the necessity of studying mediator and peptidergic systems of each subcortical structure in order to understand their significance in the mechanisms of the conditioned reflex is raised.

[The participation of brain mediator and peptidergic systems in the mechanisms of the conditioned reflex]

In dogs with implanted chemotrodes and microelectrodes, the role of acetylcholine-, dopamine-, GABA- and P-ergic systems of the caudate nucleus and amygdala in positive and inhibitory conditioning, was studied. Activation of the same transmitter system in different structures could exert different behavioral effects, whereas activation of different transmitter subcortical systems could induce the same behavioral responses. The effects of activating or blocking agents upon the mediator subcortical system depended on the functional state of the nervous-system at the moment of administration as well as on the site of administration. It seems difficult to predict a contribution of one or another subcortical structure in organization of behavioral acts.

Reorganization of activity of neurons of orbital cortex during formation of classical second-order conditioned reflexes

The reorganizations of the activity of neurons in the orbital cortex during the formation and realization of classical first- and second- order conditioned reflexes were studied in chronic experiments with eight dogs. An analysis of the histograms of the distribution of between-impulse intervals, poststimulus histograms, and the changes in the average discharge frequency showed that the responses of neurons to the presentation of a first-order or second-order conditioned signal (for a second-order reflex) undergo dynamic changes with the development and strengthening of conditioned connections. The pattern of impulse activity during the action of a conditioned signal approximates in form the pattern of discharges during the action of reinforcement. The data are discussed in light of E. A. Asratvan's concepts of the mechanism of formation of complex forms of conditioned reflexes.

Involvement of the amygdala in evaluating the biological significance of conditioned stimuli

The destruction of the amygdala in cats and dogs causes the animals to stop responding adequately to signals of various biological significance; the curves of change in the amplitude and probability of appearance of EPs in the sensorimotor cortex lose the maxima characteristic of intact animals at frequencies of 0.8, 1.6, and in the band from 2.0 to 3.0 kHz, which are the format frequencies of certain communicational signals in cats. The assumption of a signal (food) significance by an indifferent stimulus, earlier without any biological meaning, finds reflection in the neuronal activity of the amygdala, which begins to respond to this signal as if to an unconditioned stimulus. On the basis of the above factors, the role of the amygdala is discussed in the evolution of the biological significance of conditioned stimuli and the differentiation of the afferent influences that reach it.

[Rearrangement of the activity of orbital cortex neurons during second-order classical conditioning]

In chronic experiments on 8 dogs, rearrangements of unit activity were studied in the orbital cortex in the course of classic conditioning of the I and the II order. Histograms of the interspike intervals distribution changes of the mean firing rate revealed that, in the course of conditioning, the neuronal responses to presentation of conditioned stimuli of the I and II order (for the II order reflexes) underwent dynamic changes. The unit activity pattern under the effect of a conditioned stimulus approximates the form of the pattern in reinforcement. The data are discussed in the light of E.A. Asratian's ideas of the mechanism for formation of complex forms of conditioned reflexes.

[Role of the amygdala in the evaluation of the biological significance of conditioned stimuli]

Lesions of the amygdala in cats and dogs prevent some animals to respond adequately to signals of different biological significance; the amplitudes and probabilities of EPs appearance in the sensomotor cortex lose their maximums at 0.8 and 1.6 frequencies within the range of 2.0 to 3.0 kHz which are formant ones of some communication signals in cats. Rendering an indifferent stimulus a signal, i. e. food significance, becomes reflected in the amygdala neuronal activity, the amygdala starting to respond to the signal as if it were an unconditioned stimulus. The data obtained are used to discuss the role of amygdala in assessment of conditioned stimuli biological significance as well as in differentiation of incoming afferent influences.

[Effect of electric stimulation of the amygdala on orbital cortex neurons during learning and performance of a conditioned alimentary reflex]

The influence of stimulation of the amygdala nuclei complex on the orbital cortex neurones during the formation and realization of the alimentary conditioned reflex was studied in chronic experiments on three dogs. In the course of alimentary conditioning, a qualitative change of the histograms of distribution of interimpulse intervals (III) took place. Other parameters of spike activity, also underwent changes: the mean frequency of discharges and the degree of regularity of the spike flow. Single stimulation of the amygdala decreased the mean frequency of discharges of the orbital cortex neurones, diminished the secretory conditioned reflex, reduced the regularity of the spike flow and qualitatively changed the III distribution histogram. An attempt has been made to explain the mechanism of action of the amygdala nuclei stimulation on the conditioned reaction.