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This work was carried out on the model of cognitive set to facial expression under conditions of high load on working memory by lengthening interval between the facial and triggering stimuli to 8 seconds. The aim of this work was to try to reveal, there is the phenomenon of correspondence between the dynamics of gamma- responses (21-60 Hz) to the facial-stimuli and the real "success" of the job (number of mistakes in performing a task): To do this, we used a different method of estimating the power compared to the wavelet transform, as if it is applied in a previous worksuch a dependending was not revealed. In this paper we analyzed the index of the average amplitude, built in a similar method specific variation to estimate the power of gamma responses (range: gamma1-21-40 and gamma2-41-60 -Hz), which revealed correspondence between patterns of gamma responses and the number of subjects admitted mistakes. The obtained results allow us to consider gamma2-responses to facial stimuli as electrographic correlate of states (the so-called their gamma code) corresponding to the adequacy of real actions of the subject at the test under the same conditions of 8-second interval between the facial and trigger stimuli.

Power EEG gamma-band (21-60 Hz) in the process of forming and testing the cognitive set on the face expression is seen in conditions of the model, which provides a higher load on working memory by lengthening the intervals between the target and trigger stimuli to 8 s. The results are compared with data from previous experiments with increased load in the form of additional cognitive tasks, when there was an increase of gamma responses by "success" of the job subjects. In this study, the responses to set-stimuli were observed significant lower (relative to prestimulus period) in all groups of subjects that were treated as inhibition of gamma activity. Significant differences in the levels of power gamma-band between the groups were identified by comparing the set up steps (forming and testing), and frequency-bands. The second important difference is the absence of differences in the dynamics of power patterns gamma2 (41-60 Hz) between groups of subjects depending on the "success" of the job. We present arguments to substantiate the "paradoxical" results in the conditions of use of the plant model.

In the context of understanding of the mechanisms of cognitive human accounting functional role in these processes of neocortical gamma activity, the science progress of the 21st century at least three new logically related directions are outstanding to: 1) combination with intracranial recordings by functional magnetic resonance imaging (fMRI) has indicated a closely correlation between the level of power of high gamma-band (90-150 Hz) at corresponding localization and the level of blood oxygenation (responses BOLD; blood oxygenation level dependent), which provides an estimate of the dynamics of power in aspect of metabolic resources; 2) results parallel evaluation of parameters gamma activity (frequency, bandwidth, amplitude) in combination with the size of BOLD responses and the GABA concentration as measured by magnetic resonance spectroscopy, formed the basis of hypothesis about the individual peculiarities (specific features) of the subject (trait); 3) new methods of measuring the phase synchrony of gamma frequencies has created the phenomenon of cross-frequency interaction (cross-frequency coupling, CFC) between phases of gamma oscillations with theta, alpha waves. This phenomenon is considered by some authors as the basis of interrelations of different separated networks, possibly providing approach to understanding of various aspects of defining the mechanisms of cognitive processes.

A review. Studies in the period of 2009-2011 are discussed, in which a new phenomenon in human EEG was found out, i.e., personal (individual) features ofneocortical gamma activity in parameters such as amplitude, frequency and width of the gamma band. This phenomenon was revealed in induced responses to visual stimuli in people under conditions of repeated research (after different time intervals - hours, weeks, months). The findings suggest the necessity of development of the metric system for assessment of this phenomenon and corresponding estimation of personal features of the gamma band and their stability (reliability), which would allow interindividual differences to be revealed.

A review. The problem of the functional significance of gamma-band EEG in different cognitive paradigms, including the aspect of the gamma-band heterogeneity (different origin and functional significance of "low gamma" and "high gamma").

The dynamics of power of short-term (0.8 s) induced responses to facial stimuli (wavelet transform in the 15-60 Hz band) were assessed in the study of the visual cognitive set under conditions of different loads on working memory in two groups of subjects. Subjects of the first group had to react only to facial stimuli (n = 29), whereas the second group solved an additional task loading the working memory (they had to find a target stimulus in a matrix of letters, n = 35). We estimated wavelet spectra in the occipital, temporal, central and frontal areas of both hemispheres. In both groups of subjects with the plastic form of set, the power level in the gamma2 band (41-60 Hz) was significantly higher than in subject with the rigid form. In group A at the set-testing stage, the largest increase in the gamma2 band was related to the central areas of the left hemisphere. In more complex situation (group ), the increase in power in the gamma2 and gamma1 (21-40 Hz) bands was observed in the occipital and temporal areas of both hemispheres. At the same time, the EEG power of the central areas in these gamma bands was significantly lower. In the frontal areas there were no significant differences in the dynamics of power between the subjects of both groups.

Power spectra of cortical potentials of baseline activity during interstimuli intervals (4 s; Fourier transform in the frequency band of 1-60 Hz) and short-term (0.8 s) induced responses to facial stimuli (wavelet transform in the 15-60 Hz band) were assessed in the study of the visual cognitive set to facial expression. Significant differences between groups of subjects with different set rigidity were observed only at the set-testing stage. Estimation of the short-term (0.8 s) induced responses of the wavelet spectra in the group with plastic set revealed an increase in the power (in comparison with the power of background activity) of the gamma2 band (41-60 Hz) in the left hemisphere of the temporal, central and occipital areas, whereas in the group with rigid set these power spectra decreased. At the same time the power in the gamma1 band (21-40 Hz) was significantly lower (at the same level with the rigid form), indicating a discrete nature and functional selectivity in the gamma frequency band.

Interhemispheric relations of the EEG power in the 1-60 frequency band were studied at the stages of formation and testing of the cognitive set to facial expression. Different topographic asymmetry patterns were revealed in subjects with different set plasticity. In subjects without behavioral actualization (n = 11) of the set at the stage of set formation, EEG power in the gamma band (21-40 and 41-60 Hz) prevailed in the frontal areas of the right hemisphere, whereas the power of electrical oscillations in the bands of 2-7 and 8-13 Hz was higher also in the frontal areas but of the left hemisphere. At the stage of set testing, this basic topographical asymmetry pattern persisted. Formation of the set in subjects with pronounced actualization (n = 18) was characterized by another topographical asymmetry pattern: a significant excess of the power of gamma oscillations was observed in the posterotemporal and occipital areas of the left hemisphere, whereas the power of oscillations in the bands 2-7, 8-13, and 14-20 Hz was higher also in the posterior areas but of the right hemisphere. No asymmetry in the EEG power was observed in these subjects at the stage of set testing.

Power spectra of cortical potentials in the frequency band of 1-60 Hz were estimated in 29 healthy subjects in the states of rest with the open eyes, after listening to instruction, and in prestimulus periods at the stages of forming and testing of the visual cognitive set to facial expression. Comparative assessment of the power spectra in five frequency bands 2-7, 8-13, 14-20, 21-40 and 41-60 Hz revealed a significant decrease in the power for the frequencies of 1-20 Hz and its parallel increase in the band of 21-60 Hz in all the states under study as compared to the state of rest. At all the set stages, interregional differences in the EEG power were the highest in the bands of 1-20 and 41-60 Hz and the lowest in the band of 14-20 Hz. Significant differences between the "plastic" and "rigid" groups in the power dynamics were observed only at the set-testing stage. Thus, in subjects with the plastic set, the power of the gamma-frequency band was more frequently higher than in subjects with the rigid set.

Prestimulus EEG power spectra from different cortical areas in frequency band 1-60 Hz were studied at a stage of formation of the cognitive set to facial expression. Diversity of individual power spectra of baseline EEGs, especially in gamma frequency band 41-60 Hz makes averaging individual spectra impossible. The authors pioneered in finding that, in prestimulus periods, EEG frequencies 41-60 Hz were of higher information value than frequencies 1-20 and 21-40 Hz. The highest power of the gamma frequencies was revealed in the frontal areas of the right hemisphere in subjects with a plastic set. In the group with a rigid set, gamma frequencies of high power prevailed in the posterotemporal and occipital areas of the left hemisphere.

A review. The article dedicated to the centenary of academician Mikhail Nikolaevich Livanov briefly outlines the history of development of his original concept of the functional significance of the brain potential's spatial synchronization phenomenon as a possible way of studying systemic organization of the brain electrical activity. The new parameter of "space" introduced into neurophysiology by M. N. Livanov made it possible to research the earlier unknown aspect of the brain activity. Livanov's ideas have been developed in many studies of the late decades of the XX century. In the review, much attention is given to specific functional significance of this phenomenon in a broad frequency band 1-250 Hz, especially, during instrumental learning. Energy (power spectra) and coherent-phase characteristics of cortical potentials in traditional (1-30 Hz), gamma-(30-80 Hz) and high-frequency (80-250 Hz) bands are compared. The problem of linear and nonlinear processes in the organization of the brain potentials is mentioned.

Power spectra of short-term (less than 1 s) EEG-reactions (in the frequency band of 1-225 Hz) were studied in dogs in the course of instrumental food conditioning. These reactions were observed in different areas of the cortex in response to positive and differentiated conditioned stimuli. Regional features between the spectra were found both in the power level and frequency structure. The power of the reactions in the visual and parietal areas of the left hemisphere was higher than in the motor areas. Power spectra of reactions to differentiated stimuli were significantly lower than the spectra of reactions to positive stimuli mainly owing to the high-frequency components (80-225 Hz). In these both cases, prestimulus power spectra did not differ. The frequency structure of corresponding EEG-reactions consisted of individual spectral peaks, mainly both gamma (30-80 Hz) and higher-frequency (80-225 Hz) bands.

Power spectral (in the broad frequency band of 1-225 Hz) of short-term (less than 1 s) EEG reactions were studied in dogs in the course of instrumental food conditioning. These reactions appeared in different cortical areas in response to differentiating signals under conditions of both adequate and erroneous responses. The EEG power of such reactions was several times lower as compared to responses to positive signals, mainly, at the expense of the frequencies in the band of 90-225 Hz (the power of which was higher than that of the traditional band of 1-30 Hz and the gamma band of 30-80 Hz). The frequency composition of EEG reactions accompanying adequate responses was defined, mainly, by discrete subgroups of high-frequency components. During erroneous responses, the discrete structure of the corresponding EEG reactions was broken.

A review. Current views of the so-called binding problem, which considers hypothetical mechanisms of perception of sensory stimuli and formation of their corresponding Gestalts (internal images) are discussed. The mechanism of intensification of synchronized reactions of cortical electrical activity in the gamma band frequency (30-80 Hz) is the basis of the most popular point of view of "binding". The article considers the evidence for the functional significance of the high-frequency components exceeding the gamma-range (to 200 Hz) obtained by the author, the origin of these oscillations, and conditions of their focal derivation. The problem of "binding" and stages of instrumental conditioning (a stimulus, perception of the stimulus, and its transformation into a signal) as well as significance of the context in learning and formation of tonic states ensuring the realization of phasic reactions is discussed. Forms of "binding" at the final stage of conditioning (selective attention) are considered. The question is posed as to whether "binding" is exhausted only by the mechanisms of synchronization of activities of large neuronal populations and only in the frequencies of the gamma range.

Coherent-phase characteristics of cortical potentials (1-220 Hz) derived from different cortical point of both brain hemispheres of dogs were analyzed in the state of selective attention developed in the course of instrumental food conditioning. Among the compared cortical points, functional groups were found that were probably of priority for the state of selective attention. Values of coherence function between these derivations (an assessment of temporal relations) were at a certain optimal level (about 0.7), predominantly, in the frequency ranges of 1-15 and 40-200 Hz. Under such conditions, if the average phase shifts between the potentials were near zero, phenomenon of potential synchronism was formed. In case of significant phase shifts, phenomenon of asynchronous temporal relations with a certain spatial direction developed.

The state of selective attention was studied in dogs in the course of instrumental conditioning. During interstimuli intervals, this state was manifested in the state of strained waiting for conditioned stimuli. Electrical activity of different areas in both hemispheres was analyzed using the Fast Fourier Transformation. It was shown that in the process of development of selective attention, the high-frequency EEG components (40-200 Hz) in the motor area of the right hemisphere and the visual and parietal areas of the left hemisphere had a predominant significance over the traditional EEG frequencies of 1-30 Hz. The state of selective attention was characterized by another functional mosaic organization of the neocortical potentials.

The study was aimed to reveal the subbands of correlated changes in power spectral density of brain electrical activity (EA), including the low-voltage (up to 10 microV) high-frequency (HF) components (40-200 Hz) in dogs during instrumental conditioning by means of factor analysis. The values of the EA spectral density in interstimulus intervals calculated with a resolution of 1 Hz were used for subsequent factor analysis (the standard principle component technique with varimax rotation). Twenty factors could explain about 80% of total variance. The groups of frequencies which were presented by comparatively narrow peaks (2-3 points) of high loads (more than 0.6) of single factors ("stable" factors) were taken into consideration. In the process of conditioning the factor organization of the EA became substantially complicated, the number of the "stable" factors increased. It was originally shown that the high loads of these factors divided the HF band in comparatively narrow frequency subbands, which appear to reflect the functional mosaics in the neocortex.

The EEG phenomenon was studied of high-frequency bursts (60-70 Hz, 70-80 mcV) in electrical activity of dog's neocortex (EA, 1-200 Hz) in the process of instrumental conditioning. These bursts of high-frequency oscillations appeared at the generalization state of the conditioned reflex during interstimulus intervals at the background of dominant EA of the lower frequency and voltage (10-40 mcV). Application of the developed by us novel strategy of the primary analysis of EA realizations (in particular, inhomogeneity coefficient) enabled estimation of the amplitude-frequency EA inhomogeneity, namely, high-frequency bursts. The regional peculiarities of the high-frequency bursts were revealed by means of the original technique based on the expansion of EA oscillation into a system of half-waves and construction of distribution maps on the basis of their parameters. The presented data verified our earlier findings obtained using other techniques (FFT analysis and factor analysis). These data testify to differential participation of cortical areas (even those which are close to each other within a distance of 3-5 mm) in the spatio-temporal organization of potentials characteristic for a given learning paradigm.

At present, the significance of high-frequency (HF) components in brain electrical activity (EA) is widely discussed in literature. In particular, the gamma range of human EEG is considered as one of the indices of cognitive activity. In the paper a review is presented of the author's own data concerning the functional estimation of low-voltage HF components of the neocortical EA recorded in the broad band (1-100, 1-256 Hz) in the course of instrumental conditioning in dogs. Three different techniques of EA analysis were used in the study: 1) fast Fourier transformation (FFT) of EA in a broad band, 2) developed by us alternative method of non-harmonic expansion of the EEG curves taking into account their shape, 3) factor analysis of the EA spectral densities. Combination of these techniques allowed us to obtain some novel evidence indicative of high informativity of the HF fluctuations. Spatial cortical localization of the HF components of the EA is much more expressed in comparison with the traditional 1-30 Hz range. Results of factor analysis suggest functional heterogeneity of the HF band. Obtained data open new ways for researches concerning the phenomena of the functional mosaics in the neocortex as one of fundamental mechanisms in brain activity organization.

The qualitative techniques are considered of mathematical description of curve inhomogeneity which adequately reveal non-stationary fragments in EEG samples with a pseudorandom process. The introduced inhomogeneity coefficient turned to be a sufficiently adequate indicator of the presence of short-term high-frequency bursts in the electrical activity of dog's brain and a sensitive index for discrimination of quasihomogeneous fragments by the level of "general activation". It is shown that the values of this coefficient reflect the individual features of the brain electrical activity of the animals and its dynamics in the process of alimentary motor conditioning. At the same time, this index is ineffective in revealing the regional differences. A novel approach is developed for signal inhomogeneity description which is based on the traditional harmonic analysis (Fourier transform).

The study was aimed to reveal frequency ranges of correlated changes of power spectral densities of the brain electrical activity (EA) including the high-frequency components (HFC) in dogs (4 animals) by means of factor analysis technique. Spectral densities of EA in different cortical areas and olfactory bulb were factored. Relationships between the structure of the selected factors both by the parts of the total variance determined by them and their frequency loads suggest the regional and individual EA differences. In the process of learning (elaboration of motor skill of pressing the food-dispenser pedal with a forepaw) the factor organization of the EA became substantially more complicated, mainly, in the HFC-range (40-170 Hz). This was manifested in formation of narrower frequency subbands of the HFC each of which being highly loaded (0.7-0.8) by one of the factors. The evidence obtained by means of the FA was completely verified using original version of cluster analysis.

Dynamics of parameters of low-voltage high-frequency components (HFC; 40 Hz and higher) of electrical activity (EA) of the brain in a broad frequency range (1-256 Hz) was studied in dogs in the process of conditioning using correlation and spectral analysis. Motor skill of pressing the pedal of the food dispenser in response to presentation of sound stimuli was elaborated. Spectra of power, coherence and phase of EA were studied in interstimulus intervals (2-3 minutes) and intervals (1 sec) of EEG reaction to conditioned stimuli preceding the motor response. It follows from the distinctions between the parameters of EA at these states that underlying them mechanisms are different. It is assumed that the dynamics of HFC (40-170 Hz) in interstimulus intervals (intensification of HFC and dominance of small phase shifts) is an expression of cognitive activity (forming of the internal integral image of forthcoming activity). Characteristics of EEG reactions to the conditioned stimuli (increase of phase shifts between potentials) are regarded as a "motor program" which ensure direct realization of multicomponent motor reaction.

The work was aimed to reveal the functional significance of separate narrow-frequency bands in the high-frequency range (40-200 Hz) of brain electrical activity of dogs in the process of lever-pressing instrumental conditioning. In order to divide this range into separate bands we applied one of the methods of multivariate statistics, factor analysis (FA) with varimax rotation. Values of function of spectral density in the wide range (1-200 Hz) were factorized. The structure of factors reflected both regional cortical characteristics of electrical activity and individual features. Conditioning induced changes in factor description of brain electrical activity mainly in the high-frequency part of the spectra. A number of new factors appeared which divided high-frequency band of the brain activity into narrower parts with definite functional significance.

Parameters of EEG recorded from some areas of the cortex and olfactory bulbs were studied during lever-pressing alimentary conditioning in dogs and analysed using FFT in a wide frequency range (1-100 Hz). Parameters of electrical activity in the cortex ans olfactory bulbs were shown to have different dynamics. Power level of cortical potentials increased in the high frequency band (40 Hz and upwards) and that of the olfactory bulbs increased in both high frequency and alpha bands. Coherent-phase characteristics of the cortical potentials give evidence that in the process of conditioning more stable relations establish between activities of different cortical areas in both high frequency and alpha bands than in the state of quiet wakefulness. At the same time relations between potentials in the cortex and in the bulbs were characterized by the larger phase shifts, increase of coherence attributed only to the high frequency but not traditional bands. Possible role of the alpha frequencies along with the high frequency band in the process of information processing is discussed.

EEG reactions to positive and differentiated signals were compared during lever-pressing alimentary conditioning in dogs by means of described by us earlier non-standard forms of EEG analysis in a wide frequency band (1-256 Hz). Findings concerning EEG reactions to positive stimuli, confirmed the earlier obtained data on a high representativeness of the high-frequency components of dog's EEG. EEG reactions to differentiated stimuli were also excitatory. Developed by us techniques allowed us to show some quantitative characteristics of these reactions. Diversity of expression of high-frequency components in different dogs, accompanied by similarity of their effector reactions (absence of movement), was considered as a reflection of individual features of their CNS.

A new method of EEG coding (alternative to classical FFT) was worked up. It allowed to compensate for limitations of FFT and to obtain new information on the shape of EEG curve reflecting peculiarities of oscillations of potentials. Proposed technique of EEG coding seems to be adequate for revealing individual and regional features of EEG and their estimation at different stages of instrumental conditioning. Data obtained using this method confirm the reality of high frequency EEG components of small power. In addition, by the method used the intensification of slow wave EEG components was demonstrated in some cortical regions which could not be revealed by FFT.

Coherence-phase characteristics of cortical and bulbus olfactorius (BO) potentials were studied during the lever-pressing alimentary conditioning in dogs. These parameters were considered as the basic ones for forming the interareal functional relations in the process of conditioning. Variety of distributions of phase shifts between potentials in a wide frequency band (1-100, 1-256 Hz) at wakefulness permits to think about the spatial-successive processes participating in organization of the brain electrical activity. Values of phase shifts between cortical potentials were significantly less then those between the cortex and BO. At stable conditioned responses phase shifts between the cortical potentials diminished considerably due to intensification of the spatial synchronization processes while those between the cortex and BO increased to a higher degree.

Background electric activity was studied of different neocortex areas in interstimulus intervals at the stage of generalization during elaboration of motor alimentary conditioned reflexes in dogs. For this stage the appearance is typical of short-term (0.1-0.3 s) packs of high frequencies (above 40 osc./s) significantly exceeding the adjacent initial background by frequency and amplitude (along side with motor interstimulus reactions). The index of specific variation, elaborated by us, allowed to single out this EEG pattern in the initial realizations of the background activity during their input in the computer. With the purpose of further evaluation of the above phenomenon parameters non-standard approaches of computer analyses were used, directed to decomposition of the EEG curve into the system of oscillations and receipt of corresponding amplitudes frequencies distributions (maps). It was shown, the described high frequencies packs were localized on these maps in definite sufficiently compact places.

Electrical activity was studied of five different regions of dogs neocortex in inter-stimuli periods in the process of learning of motor habit of pressing the feeder pedal. Epidural electrodes were used. The processing was performed by means of correlation-spectral analysis in a wide band of 1-256 Hz. Values of cross-correlation coefficients, spectra of power, coherence and phase shifts were obtained. In the process of the habit consolidation the high frequencies power increased significantly (within the limits from 60 to 150-170 osc/sec), as well as the part of high coherence (over 0.75), falling on these limits, with low phase shifts. Relatively slow-wave oscillations (1-20 osc/sec) underwent changes of considerably lesser degree. A greater locality of high frequencies (in comparison with the traditional range of 1-20 Hz) was shown. The question of the nature of high frequency EEG components is discussed.

With the purpose of levelling the restrictions appearing at the EEG correlative-spectral analysis, particularly of short (1-2 sec) realizations, as a result of Fourier transform, a new algorithm is elaborated of decomposition and analysis of bioelectrical activity. The created algorithm of complete EEG reduction to the list of oscillations singled out has been tested by a corresponding program. It provides for the measurement of parameters of concrete characteristics of the curve, and the adequacy of decomposition is ascertained by the exact restoration from the list of oscillations of the initial EEG. The method shows good sensitivity to the revealing of transient EEG phenomena and also regional specificity of the cortical bioelectrical activity.

Phase-coherent characteristics of neocortex background electrical activity were studied in a wide frequency range (1-100 Hz) during interstimulus periods in the process of elaboration of motor alimentary conditioned reflexes in dogs. It was shown that the process of learning led to a considerable increase of the part of high (greater than 0.75) and significant (0.5-0.75) coherences, and also of small (0 +/- 15 degrees) and accounted (+/- 16 - +/- 30 degrees) phasic shifts as compared with the state of calm wakefulness. This increase lay mainly in the high-frequency range (40-100 Hz). The analysis of the interregional relations showed that they differed not only by values of phase-coherent characteristics, but also by distributions of the latter. The obtained data testify that the state of activation is manifested both in the rise of frequency of potentials oscillations and in the increase of their synchronization.

During elaboration of a stereotype system of defensive conditioned reflexes in dogs (Pavlov dynamic stereotype), a correlation spectral analysis was made of electrical activity in the neocortex. With a stable dynamic stereotype, substantial changes of background electrical activity were observed in the interstimuli periods, manifested in a significant growth of linear relations of cortical potentials at certain frequencies. This was expressed in separation from the wide-band random process (involving background activity before the formation of the dynamic stereotype) of definite, relatively narrow ranges of frequencies which formed the high coherence of the processes. No such changes of electrical activity were observed in conditioning without a stereotype; this points to special mechanisms of the dynamic stereotype, which differ from those of ordinary conditioned reflexes.

The responses of 288 neurons with background activity in the first auditory cortex were investigated using glass microelectrodes in chronic experiments on cats at rest (123 neurons) and during elaboration of a defensive conditioned reflex to sound stimulation (165 neurons). At rest 43% of recorded neurons did not respond to the sound stimulus. Pronounced inhibition of background activity prevailed among responding neurons (about 60%). The conditioning caused an increase (to 72%) in proportion of neurons responsive to the sound stimulus, appearance of tonic reactions, as well as an increase in frequency of bursts and in proportion of activation type responses. It is suggested that these changes indicate the enhancement of neurons excitability in the zone under study during conditioning.

Using glass microelectrodes, the impulse activity of auditory cortex neurons was studied in chronic experiments on cats. It was shown that an increase in frequency of the background activity occurring in many neurons during conditioning was often observed prior to the appearance of conditioned motor reactions. Comparison of mean frequencies of the background activity and corresponding evoked activity shows, on the one hand, the nonlinear dependence between them and, on the other hand, the prevalence of activation reactions as compared with inhibitory ones. Some levels of background activity were distinguished corresponding to mean evoked activity frequency ranges. Background activity analysis performed prior to the presentation of the conditioned stimulus and after its cessation (aftereffect) shows that at stable conditioned reflex mean frequencies in these periods are close to each other.

The work is a logical continuation of previous studies (analysis of the background electrical activity in the band 1-100 Hz in interstimulus intervals in the process of lever pressing alimentary conditioning in dogs) and it is dedicated to correlation-spectral analysis of prestimulus periods and EEG-reactions to conditioned stimuli, previous to conditioned lever pressing. Visually the EEG reactions present discharges of high-frequency (40-100 Hz) synchronized activity preceding for 40-300 ms the beginning of the changes in EMG of the "working" limb. It is shown that EEG reactions are characterized (in comparison with the background activity) by a higher energetic level and a greater expression of the high coherence (I greater than 0.75) and also by greater phase shifts, in counterbalance to the domination of little phase shifts in the background activity. It is assumed that the patterns of EEG reactions may participate in trigger mechanisms either eliciting conditioned motor reactions (to positive conditioned stimuli) or preventing them (to inhibitory conditioned stimuli).

A system of food-procuring conditioned reflexes (dynamic stereotype after I.P. Pavlov) was elaborated in dogs. In the interstimuli periods, 0.6 to 0.8 sec. prior the action of the conditioned stimulus, they exhibited a "state of expectancy" characterized by an increase of frequency (up to 80 per sec.) of potential oscillations of a small amplitude (20 to 30 mcv) and their pronounced sychroneity, predominantly in the anterior parts of the neocortex. The conditioned signal acting against such background produced specific reactions in the form of a limited number of bursts (3 to 4 in 0.5 sec.) of highfrequency (up to 100 per sec.) synchronized activity (HSA) of considerable amplitude (50 to 60 mcv) which always preceded conditioned reactions, being in certain temporal relations with them. A correlation-spectral analysis has shown that in the HSA period, electrical activity became considerably more regular; in the intensity spectra the extreme frequencies of the analyzed band (5 to 7 c/s and 90 to 100 c/s) became prominent, and in most cases high values of the coherence function were due to them. HSA reactions are regarded as a major link in the trigger mechanism of conditioned food-procuring reactions.

Autospectral characteristics (ASC) of potentials of different neocortical areas of dogs in a state of quiet wakefulness were studied in a wide frequency band (1-100 Hz) by means of correlation-spectral analysis. A transition from evaluation of the mean power tendencies to a construction of distributions of different power levels for each of five arbitrarily chosen frequency bands permitted to reveal regional differences in ASC of each animal as well as interindividual EEG distinctions. The regional differences observed in all frequency bands (though not equally expressed) including the higher ones indicate not only the informativity of high-frequency components of electrical neocortical activity but also their neuronal origin.

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.

Background electrical activity of different areas of the neocortex was studied at interstimuli periods during elaboration of food-procuring (instrumental) conditioned reflexes in dogs. By using the complex of EEG parameters obtained after a correlation-spectral analysis, it was possible to provide differentiated EEG characteristics of such externally similar conditions as rest in a situation of food-procuring and in an indifferent situation. Further, it has been found that the background activity parameters significantly differ in one and the same situation of food-procuring, depending on the functional state (passive rest and activation of attention). The data obtained point to the informative nature of background electrical activity of the neocortex, whose parameters reflect the peculiarities of specific functional conditions.

Alimentary conditioned reflexes in the form of pressing (with an effort not less than 600 g) with a fore-leg on the pedal of a nearby feeding-trough, were elaborated by means of classical secretory technique in 15 dogs with defined typological characteristics of the higher nervous activity. The motor habit was formed in about a half of the animals. The ability to instrumental learning was assessed on a five-points scale in accordance with four stages of habit formation. The study revealed an absence of direct dependance between the obtained typological characteristics of the animals and their ability to instrumental conditioning.

In chronic experiments on cats the neuronal responses (recording by means of glass microelectrodes) of auditory cortex I were studied during elaboration of a defensive conditioned reflex to a sound stimulus. During conditioning the biphasic reactions with a rather short-latent (50-100 ms) and more long-latent (400-500 and 800-900 ms) activation were predominant. The neighbouring neurons whose responses were recorded by the same microelectrode were involved into the activity more intensively. A differentiating stimulus in 70% of applications caused distinct changes in neuronal activity (predominantly of activation type). Analysis of the dynamics of responses of the same neuron during a great deal of combinations and its comparison with the formation of a motor reaction showed no direct correlation between the two events.

The results of statistical computer analysis of 366 realizations of the background activity of 181 neurons from the primary auditory cortex (field 50) in vigil cats (14) at rest and during defensive conditioning are presented. In both states the parameters of background activity in most neurons differed from completely random succession. The conditioning evoked a stable elevation of the frequency of background activity during interstimulus intervals, an increase in stability of the background impulsation as regards its average frequency and variation coefficients of the duration of interspike intervals, as well as an enhancement of the number of neurons showing different types of association between interspike intervals.

Power spectra of electrical activity of different dogs neocortical areas within a wide frequency band (1-100 Hz) were studied by correlation-spectral analysis during elaboration of motor (pressing the pedal) alimentary conditioned reflexes (CR) to acoustic stimuli. Considerable redistribution of autospectra power (ASP) within one of the five selected frequency ranges (from I to V, 20 Hz each) was observed. The frequencies of III-V ranges (41-100 Hz) were the most reactive; the degree of power increase after CR stabilization was determined by its initial level before CR elaboration which significantly differed in various animals. The weaker were presented in the EEG high frequencies before learning, the higher was the increase of their power in the process of elaboration of the given type of CR, and on the contrary, a definite level of "saturation" was preserved. Relatively low frequencies (below 20 Hz) were characterized after CR elaboration by lowering of the power. Deliberate lowering of the alimentary motivation led to a weakening of CR and power decrease (in comparison with stabilized CR) of all frequency components; however, its level remained higher, than before CR elaboration.