[Chaotic non-linear dynamics of alpha-band of the EEg and organization of the cortical activity of P300 wave].

Variations of non-linear dynamic operations in of alpha-band of the EEG are reflected in the peculiarities of the P300 wave cortical field organization. In high-dimensional chaotic processes this field is characterized with high values of integral indices of its activity, the spatial synchronization of generating process as well as with the prevalence of P3a wave generation. The diversity of spatial combinations of P-wave sources reflects the high rate of their spatial complexity organization. The main contribution into this activity is made by symmetrical points of anterior and temporal cortical portions. In low-dimensional dynamics the spatial structure of the positive wave is simplified. It becomes less global and more differentiated. P3b wave generation prevails in this case. The values of integral indices of wave cortical field activity are reduced. The focal topography of positive waves and their sources changes. Chaotic systems of alpha-band wave generators demonstrate good controllability and high plasticity in contingent acoustic stimulation. They change their dynamic characteristics due to biofeedback control, determining thereby P-wave field organization.

[Chaotic nonlinear dynamics of prestimulus EEG and the structure of auditory evoked potentials ]. / Khaoticheskaia nelineinaia dinamika prestimul'noi EEG i struktura slukhovykh vyzvannykh potenthialov.

The dynamic pattern of a prestimulus EEG was studied by the fractal analysis technique. The character of this pattern was shown to affect the structure of cortical auditory evoked potentials (EP). A monoperiodic pattern in the control frequency band was accompanied by a formation of several new attractors with low dimensionality attributed to simultaneous functioning of several weakly connected dynamic systems with an indefinite trend of a leading process. During development of multiperiodic processes in EEG segments, the fractal analysis revealed a tendency for a formation of a single complex dynamic system with high dimensionality of the attractor. Characteristic changes in parameters of the primary and middle-latency EP components, their correlation, and factor models are related with the character of nonlinear patterns. Analysis of variance revealed the most effective role of pattern changes in the EEG alpha control band. The structure of combination of parameters of the EP primary components into connected complexes depends on the nonlinear prestimulus EEG patterns. The above predictors determine differently directed and differently pronounced changes in parameters of the middle-latency positive waves.

[The adaptive regulation of the nonlinear dynamics of brain electrical activity]. / Adaptivnaia reguliatsiia nelineinoi dinamiki élektricheskoi aktivnosti golovnogo mozga.

The reinforcing automated stimulation of the emotional positive hypothalamic areas which was contingent upon the multiperiodical events in the EEG structure increased the number of episodes with non-linear dynamics. It resulted in an increase in the frequency of the intracranial self-stimulation. Under conditions of controlled experiment a possibility was shown of the intentional experimental formation of the EEG episodes with different types of non-linear dynamics. At the stages preceding the associative learning, the application of fractal analysis enabled revealing a complex character of non-linearity in the bands of the EEG dominant frequencies with a slight tendency to a dominant process. The associative learning produced one dominant non-linear process which determined the dynamics of the whole system. The neurophysiological characteristics of the given adaptive process were determined as well as the difference between this process and the response to control stimulation.

[Changes in the indices of neuronal functional activity under the action of piracetam as a possible basis for realizing the effects of nootropic agents]. / Izmenenie pokazatelei funktsional'noi aktivnosti neironov pod deistviem piratsetama kak vozmozhnaia osnova realizatsii éffektov nootropov.

Effects of piracetam (PA, 4-20 mM) on some electric characteristics of neuron activity were studied in vitro in identified neurons of Lymnaea stagnalis. Stimulation, single-electrode voltage clamping and recording of activity of the neuron were realized via the same intracellular microelectrode. PA-induced alterations of the characteristics under study were observed in 60-70% of recorded neurons. Modifications of action potential generation threshold, of the slope and shape of steady-state membrane current-voltage characteristics and appearance of PA-induced transmembrane ion currents occurred more frequently than changes in other parameters. Typically, Ca channel blockers (nifedipine and Cd ions) reversed or reduced the influence of PA on the studied characteristics of tested cell activity, i. e., acted as PA antagonists. This suggests that realization of observed PA effects is due to its action on Ca channel functioning. Selective modification of the latter can determine development of various PA effects at the cellular level. An assumption is discussed that piracetam, being a highly efficient cellular adaptogen and modifying specifically Ca channels of cells, is capable of moving them to a new level of functioning which is necessary for ensuring complex forms of nervous activity.

[The effect of different regimens of intracellular electrostimulation on the dynamics of neuronal adaptation processes]. / Vliianie razlichnykh rezhimov vnutrikletochnoi élektrostimuliatsii na dinamiku adaptatsionnykh protsessov neironov.

Was studied the influence of rhythmic, random and contingent intracellular electrostimulation on the character of the initial spike activity of individual identified and nonidentified neurons of the isolated CNS of Lymnaea stagnalis snail under the conditions of the controlled experiment. Stimulation and recording of neuron activity were realized via the same microelectrode. In the process of neuron adaptation to the regimens of stimulation used two phases were distinguished being estimated with the help of various statistic criteria. The expression and stability of observed adaptive alterations of endogenous rhythm system were different during the phases determined. At the first phase which reflected a search for the strategy of the optimization of input external influences, the dispersion of interspike intervals and disorder of discharge patterns increased. The true neuron adaptation was developed at the second phase and observed only at contingent reinforcement. Such an adaptation was followed by steady alterations of endogenous rhythm system resulted in minimization or maximization of frequency of associative auto-reinforcements. Alterations accompanying the effect of optimization of external influences were the most expressive at the end of the epoch of corresponding contingent stimulation and remained for some minutes after its cessation. In the paper are discussed the possible mechanisms of the observed endo-neuronal adaptive reconstructions of spike activity.

[The possible mechanisms of the plastic reorganizations of neuronal activity under different regimens of intracellular electrostimulation based on data from systems analysis methods]. / Vozmozhnye mekhanizmy plasticheskikh perestroek aktivnosti neirona pri razlichnykh rezhimakh vnutrikletochnoi élektrostimuliatsii po dannym metodov sistemnogo analiza.

Effects of rhythmical, random and associative intracellular stimulation were studied in identified single neurons of isolated CNS of the Lymnaea stagnalis snail under the conditions of computer controlled experiment. By means of cluster, correlation, and factor methods of analysis were evaluated and compared changes of the character of spontaneous discharge activity induced by above mentioned modes of stimulation. Connections of the basic frequency and temporary characteristics of the endogenous activity of neurons with parameters of external influences were shown to be revealed only during stimulation associated with certain components of endogenous rhythmicity. These connections were practically absent during rhythmical and random stimulation. Three factors were separated which determine the formation of the structure of spike impulsation at application of suprathreshold stimuli. By their variables' composition the factors may be interpreted as: 1) factor of intensity of spontaneous activity; 2) factor of variability of interspike intervals; 3) reinforcing factor. Possible cellular mechanisms of adaptive reorganization of spontaneous activity under the conditions of associative influences are discussed.

[Cellular analog of instrumental behavior on single mollusk neurons during automatic intracellular electrostimulation]. / Izuchenie kletochnogo analoga "instrumental'nogo povedeniia" na otdel'nykh neironakh molliuska pri vnutrikletochnoi avtomaticheskoi élektrostimuliatsii.

In experiments on spontaneously active neurones of isolated CNS of Lymnaea stagnalis the influence was studied of automatic contingent intracellular electrostimulation on the character of spike discharge of these cells. In every tested neurone in some series of stimulation only prolonged interimpulse intervals (greater than their mean background value) were selectively reinforced in other series--only short ones. It is shown that at such contingent reinforcement both of long and short intervals 35% of neurones can directly change the frequency and the pattern of their spontaneous impulse activity to "minimize" ("maximize") the number of autoreinforcements in both regimes of stimulation, what may be considered as a cellular analog of the instrumental reflex. Control rhythmical stimulation of the same cells elicited no significant changes in the character of spontaneous activity. It is suggested that such contingent intracellular electrostimulation is biologically significant for the cell, as it elicits directed reconstruction of the initial discharge pattern, leading to minimization or maximization of the frequency of autoreinforcements. A possible contribution is discussed of such endoneuronal plastic reconstructions in the activity of the neuronal network participating in the performance and regulation of conditioned acts.

[Effect of arousing and somnogenic effects on the hypothalamus on the space-time organization of the internal connections of the somatosensory cortex]. / Prostranstvenno-vremennaia organizatsiia vnutrennikh sviazei somatosensornoi kory v usloviiakh probuzhdaiushchikh i somnogennykh vozdeistvii gipotalamusa.

Evoked potentials arising in the somatosensory cortex in response to single local stimulation of a forepaw, were recorded in cats in a state of slow-wave sleep and strained alertness elicited by electric activation of the basal preoptic area and posterior hypothalamus. Structure of connections between cortical points was studied by values of responses' amplitudes by means of correlation and factor analyses. It has been found that the organization of functional connections within the somatosensory cortex is determined by several factors, sensitive to hypothalamic influences. The most specific organization for each state is revealed at the stage of completion of the positive-negative complex of the primary response, which combines with the highest plasticity of connection formation.

[Factor analysis of the mechanisms of the structure of sleep-wakefulness cycle]. / Vozmozhnye mekhanizmy organizatsii struktury tsikla son-bodrstvovanie po dannym faktornogo analiza.

As a result of factor analysis of the structure of the cat sleep--wakefulness cycle, six factors have been defined, regarded as factors of "paradoxical sleep", "structure of slow-wave sleep", "transitions or delta-sleep", "sleep of medium depth", "stage of sleep spindles" and "delta sleep". Along with the detected certain independence of the apparatuses controlling individual sleep stages it was shown that mechanisms of paradoxical sleep may determine the organization of the entire sleep--wakefulness cycle, representing a peculiar system-forming factor. A considerable part in cessation of the fast sleep, as well as in the sleep general mechanisms is played by the apparatuses responsible for the transitional processes between the stages.

[Participation of the preoptic area in the synchronizing and desynchronizing mechanisms of the brain]. / Uchastie preopticheskoi oblasti v sinkhroniziruiushchikh i desinkhronizi ruiushchikh mekhanizmakh mozga.

The paper deals with spreading of the positive wave (P-wave), appearing in response to stimulation of the basal preoptic area (BPA) in the structures of meso-diencephalic and bulbar levels, predominantly involved into synchronizing and desynchronizing brain systems. It is shown that P-wave is mostly pronounced in the structures situated along the medial fascicle of the forebrain, its bilateral coagulation leading to changes in wave characteristics in the studied structures. Besides, after section of the medial fascicle of the forebrain pronounced inhibitory effects of the posterior hypothalamus on P-wave appearing in response to stimulation of BPA, are considerably weakened.

[Role of the median forebrain bundle in organizing the electrical activity of the neocortex]. / Rol' medial'nogo puchka perednego mozga v organizatsii élektricheskoi aktivnosti novoi kory.

Bilateral coagulation of the forebrain medial bundle in the lateral hypothalamus enhances the formation of spontaneous spindles and facilitates the recruiting response in the neocortex. This combines with a defect of desynchronizing influences of the posterior hypothalamus and the concurrent dominance of synchronizing effects of the preoptic area (PA). PA stimulation enhances the slow wave and spindle activity in the ECoG of the intact brain. After disruption of PA connections with the bulbar synchronizing apparatus the stimulation effect is manifested only in enhanced spindle activity. It is assumed that in addition to hypnogenic influences which PA shares with the parasolitary apparatus, it maintains a definite level of cortical reactivity after the onset of sleep. Elimination of the orbito-frontal cortex, as well as PA coagulation, does not prevent the appearance of spindles in the ECoG of the preparation with an intersected medial bundle, only limiting them to some extent.

[Participation of the neocortical and reticulo-hypothalamic apparatuses in the regulation of recurrent inhibition in the thalamic relay nucleus]. / Uchastie neokortikal'nykh i retikulo-gipotalamicheskikh apparatov v reguliatsii vozvratnogo tormozheniia v talamicheskom peredatochnom iadre

In acute experiments on cats a study was made into the development of the field potential of the recurrent inhibition wave (P-wave) in VPL in response to the stimulation of the somatosensory cortex. It has been found that high-frequency stimulation of the posterior medial hypothalamus results in the reduction of the thalamic P-wave brought about antidromically and in a decrease of the number of waves in the series. The effect of stimulation of the posterior hypothalamus on the processes of recurrent inhibition in the relay thalamus is to a great extent mediated through mechanisms of the branstem reticular formation. It has been shown that the dynamics of amplitude characteristics of primary sensory responses in the VPL depends on the phases of development of P-wave in the nucleus. Functional switching off of the cortex by means of loci toxic action reduces the amplitude of P-wave produced by stimulation of a point of the poisoned cortex. Spatial non-coincidence between the topography of foci of maximal activity of primary thalamo-cortical responses and the foci of maximal influences of the stimulated cortex on recurrent inhibition in VPL points to the likely involvement of the neocortical apparatus proper in recurrent thalamic inhibition.