[Brain activation levels and the significance of the stage B(I) indices in neuroses]. / Urovni aktivatsii mozga i znachenie pokazatelei stadii B(I) pri nevrozakh.

Two forms of neuroses--neurasthenia and hysteria--show statistically definitive differences in the EEG patterns. In the initial EEGs of neurasthenic patients, as a rule, more or less marked alpha-rhythm is preserved, whereas the EEG in hysteria in most cases consists of low amplitude fast frequencies ("flat" EEG) and only in 30-35% cases short episodes of alpha-waves can be recorded. In the course of medical treatment the index alpha often increases and the EEG gradually obtains normal features. One of the most favourable signs of convalescence is the renewal of the ability to develop the phase of drowsiness with the stage B in the EEG, during which the outburst of alpha-waves is recorded as a reaction to stimulation.

[Mosaicism of excitatory and inhibitory processes in populations of cortical neurons during the brain activation response]. / Mozaichnost' vozbuditel'nykh i tormoznykh protsessov v populiatsiiakh neironov kory pri reaktsii aktivatsii mozga.

Comparative analysis of multiunit arousal response in the somatosensory I and the parietal associative brain areas of unanesthetized cats revealed the initial excitation of neuronal populations in both cortical areas to be independent of stimulus modality. The greatest firing rate was observed in the 1st period of the arousal response when the brain activation was maximal. Subsequent development of the multiunit response may be either tonic or phasic. The phasic responses are predominant in the somato-sensory neuronal populations (56-87%). The multiunit tonic responses (55-85%) occur mostly in the parietal associative area. The end of the inhibition phase coincided with the end of the arousal response. The relation of the response types to unspecific brain activation, is discussed.

[Changes in the phasic activity of neuron microsystems of the somatosensory cortex of the cat during extinction of activation reactions to unreinforced stimuli]. / Izmeneniia faznoi deiatel'nosti mikrosistem neironov somatosensornoi kory koshki pri ugashenii reaktsii aktivatsii na nepodkrepliaemye stimuly.

In chronic experiments on cats, three-phasic responses of neuronal microsystems in the cortical somatic area I were studied during habituation of the EEG activation reactions. Repeated stimuli of different modalities were used: electrical pulses to the forepaw, sounds, direct stimulation of the mesencephalic RF. Simultaneously with the extinction of EEG activation reactions, the three-phasic responses of the multiunit activity (MUA) also became progressively extinct: the 1st phase of primary excitation--only a little, the 2nd phase (inhibitory)--greatly, as well as the 3rd phase--the phase of secondary excitation (if it existed at the beginning). The MUA responses to all stimuli show that these neuronal microsystems are polysensory. Relatively to the nonspecific activating RF macrosystem, the investigated neuronal microsystems are autonomous because their two functionally opposed response phases--the 1st excitatory and the 2nd inhibitory--occur against the monotonous excitatory background of the EEG activation. But in some way the neuronal microsystems are connected with the RF-system because of the parallel development of the extinction process.

[Participation of the lateral geniculate body in the mechanisms of brain activation]. / Uchastie naruzhnogo kolenchatogo tela v mekhanizmakh aktivatsii mozga.

In chronic experiments on cats with intact LGB, electrical stimulation of the latter (120-190 microA) caused brain activation with the same threshold as the stimulation of the mesencephalic RF or of the thalamic CM with 50-80 microA. With all but the geniculo-cortical connections of the LGB disrupted, the threshold for brain activation increased to 220-400 microA. After LGB coagulation leaving intact all optical tract connections to the superior colliculi and to the brain stem, the adequate cortical activation was only possible with very strong light flashes (250-1000 l). This suggests that the LGB participates in unspecific brain mechanisms and can induce cortical activation regulated afterwards by the cortex itself.

[Activation response to photic stimulation in normal cats and after transection of the afferent pathways of the mesencephalic reticular formation]. / Reaktsiia aktivatsii pri svetovom razdrazhenii v norme i posle pererezki afferentnykh putei mezéntsefal 'noi retikuliarnoi formatsii u koshki.

In chronic experiments on waking unrestrained cats with implanted electrodes the reaction of EEG activation to light stimulation was recorded in two sets of experiments in normal cats and in animals with transsection of brachia colliculi superioris that separated mesencephalic reticular system. The intensity of the activating reaction in the intact cats increased ith a rise in the light stimulus intensity. In the cats with brachia-colliculi superioris transsected there was no definite dependence on the stimuli intensity and the intensity of the activating reaction changed randomly. It is suggested that this irregularity is accounted for by blocking of the excitating afferent flow usually coming to the mesencephalic reticular formation through brachia and colliculi both from the visual pathways (ascending flow) and from the cortex (descending activation regulating flow).

[Multineuronal characteristics of brain activation during extinction of the effects of indifferent stimuli]. / Mul'inteironal'naia kharakteristika aktivatsii mozga pri ugashenii deistviia indifferentnykh razdrazhitelei.

In chronic experiments on cats, the correlation of multineuronal activity (MNA) in the somatosensory cortex with EEG activation reactions recorded at the same point was studied during the process of extinction. The MNA was discriminated in three amplitude levels and averaged by means of a computer. Three kinds of stimuli were used: electric shocks to the forepaw, sounds and direct stimulation of the midbrain reticular formation. It was found that with repetition of stimuli, the progressive inhibition of the EEG activation correlates with gradual reduction of the level of sharp increase of MNA frequency in response to stimulation, and with shortening of the poststimuli periods of prolonged frequency reduction. A minor part of neuronal populations reacted with a slowing down of the discharge frequency (e. g. to the sound and reticular stimulation). More specific frequency reactions during extinction were recorded at different amplitude levels, depending on the modality and the parameters of the stimuli and on the population type. The changes in multineuronal discharges rate were more diverse and more continuous than the EEG responses. A comparative study of both phenomena reveals only partial coherence between them.

[Multicellular spiking of the cat somatosensory cortex at rest and during spontaneous EEG activation]. / Mil'tikletochnaia impul'satsiia somatosensornoi kory koshki v sostoianii pokoia i pri spontannoi aktivatsii EEG.

In chronical experiments on unanesthetized unrestrained cat multineuronal discharges and EEG were simultaneously recorded from the somatosensory cortex by the same semimi-croelectrode. The discharges were automaticaly separated into three amplitude levels. Three types of basic multineuronal discharge patterns were classified: continuous, bursting and grouped ones. During visually similar periods of spontaneous EEG activation the multineuronal discharges exhibited different and variable changes. The amplitude discrimination method revealed at different discharge levels parallel discharge frequency rise or fall or absence of changes in the average frequency. The kind of multineuronal discharge reorganization depended on the intensity of the EEG activation. The computer analysis showed the prevalence of the excitatory effects (55%), but inhibitory changes were also rather significant (21%). The experimental data suggest a complicated and highly dynamic functional structure of the spontaneous brain activation process at the level of neuronal populations.