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Two parts of a geometrical figure are consecutively presented to healthy adult subjects in the left and right visual fields; the subjects have to compare them mentally and to decide whether these parts form a standard figure or not. Correctness of the reaction is controlled by a computer which lights up on the screen the words "good" or "error". The number of correct decisions of this visual-spatial task does not depend on the hemisphere to which information is addressed. The reaction time is substantially shorter if the information comes "directly" to the right hemisphere. Due to better training in the left hemisphere interhemispheric difference in reaction time gradually disappears in repeated tests. Training to mental "constructing" takes place only in the tests following positive feedback stimulus. Analysis of amplitude-temporal parameters of P300 wave shows that at correct decision of the visual-spatial task the level of activation in the right hemisphere is higher than in the left one.

Reaction time was recorded in adult healthy people at pauses of 80, 110, 150, 200, 300, 500 and 800 ms between the warning and the triggering stimuli. The warning signal determined the choice of reaction. The stimuli were presented to different halves of the visual field at random. 200 ms pause between the warning and the triggering stimuli is critical for the reaction time. Beginning with this interval, the reaction time was considerably reduced. When information from the triggering stimulus reached "directly" the hemisphere which was "to produce" the motor response, reaction time was considerably shorter, than at non-coincidence of these two factors. The influence of their combination on reaction time is particularly pronounced at 150-500 ms pauses between the warning and the triggering stimuli. The data obtained suggest that the decision making results in a lateralized activation of the hemisphere, which is "to produce" the motor reaction. As a rule, reaction time is not influenced by spatial location of the warning signal. The results of the work should be taken into account when organizing activity of an operator.

Recognition of short time intervals (10, 60, and 180 ms) between visual stimuli presented to the left or right hemisphere was studied in adult healthy people. The interval of 180 ms is recognized better than that of 10 or 60 ms. Learning with repeated tests with 180 ms intervals proceeds better than that with short intervals. The predominance of the left hemisphere has been revealed only for perception of 10 ms interval. The other time intervals asymmetry is not observed. It is suggested that the left hemisphere is predominant in estimation of short (less than 60 ms) time intervals. In formation of time nervous model a significant role is played by local activation of the cortical zone where the standard stimulus is addressed.

Average evoked potentials (AEP) were recorded in practically healthy subjects to "meaningless" figures and letters, presented to different halves of the visual field. Analysis of the amplitudes of AEP late components to verbal and non-verbal stimuli reveals hemispheric asymmetry. A higher amplitude of the late positive evoked response (P300) to a "direct" stimulation both by verbal and non-verbal stimuli (in the contralateral field of vision) is recorded in the left hemisphere than in the right one. Similar stimulation of the right hemisphere does not reveal sucha difference. In the left hemisphere the P300 wave is of a clearly greater amplitude to a "direct" stimulation (contralateral visual field) than to an "indirect" one (ipsilateral visual field), regardless of the nature of the stimulus. No such difference is observed in the right hemisphere. The magnitude of the late negative wave (component N200) to non-verbal stimuli is greater in the right hemisphere both in response to "direct" and "indirect" stimulations. No intrahemispheric difference has been found in the amplitude of late evoked responses of the cerebral cortex to verbal and non-verbal stimuli.

11 right-handed subjects with normal vision were examined. The analysis of latencies and amplitudes of the late AEP components elicited by verbal stimuli, presented in different halves of the visual field, revealed that the late positive evoked potential P300 to a single word with neutral meaning develops in the right occipital area with a shorter latency and a greater amplitude, than in the left one. Interhemispheric differences are not observed in "the associative" zone (presumably at the junction of the temporal, parietal and occipital areas). In the process of perception of an emotional word interhemispheric relations are considerably changed: in the left occipital area the P300 wave latency is considerably shorter, than in the right one; no differences in the amplitude of P300 are visible. The changes in P300 wave latencies reflect a local nonspecific activation of the cortex, directly connected with the analysis of the emotional verbal signal. The obliteration of interhemispheric differences in P300 wave amplitude is largely due to background emotional excitation.

In the course of formation of temporary connection between a nonverbal visual stimulus and an emotional word, interhemispheric functional relations are significantly changed. The conditioned stimulus elicits local activation mainly in the visual cortex of the left hemisphere, which results in reversion of interhemispheric relations during latency of cortical evoked response. In the "associative" area, the elaboration of the temporary connection does not affect latency and amplitude of the evoked response to the conditioned stimulus. Extinction of the temporary connection and, hence, recovery of the interhemispheric functional relations observed before its elaboration, proceeds slowly, and sets in after 100-150 presentations of the signal without reinforcement.

The wave P300 was recorded in both hemispheres in order to study interhemispheric differences in the process of perception of unrecognized verbal stimuli. The stimuli--unrecognized words, neutral and emotional--were alternately presented at random in the left and right visual fields. In response to an unrecognized emotional word, the amplitude of the P300 wave increases diffusely in both hemispheres, as compared to the response to a neutral word, with no changes in interhemispheric differences. They change considerably in the process of an "unaccountable" emotion, caused by an unrecognized word, due to unilateral activation of the right hemisphere. The conclusion is made on the predominant role of the right hemisphere in the cortical organization of such unconscious function as "unaccountable" emotion.

Recordings of the P300 waves in left and right hemispheres in response to neutral and emotionally significant words corroborate the rightfulness of the principle stating that any psychic function, for instance emotion, is organized and controlled by means of a close and complementary collaboration of both hemispheres. A predominance of a hemisphere manifests itself in organizing a certain stage of the integral emotional function.

The study was made on healthy adult subjects. The reaction time of the hand (RT) was measured under two conditions: 1) the choice of reaction (right or left hand) is determined by the nature of the warning stimulus; 2) decision on the choice is taken, depending on the second, trigger stimulus. Stimuli are presented at random sequences to different visual fields. The reaction time to the visual signal presented to the visual field ipsilateral to the hand is significantly shorter (by 15 to 26 msec) than to the stimulus in the contralateral visual field. In a simple motor reaction, when no discrimination of trigger stimulus and the decision on the choice of reaction is required, a hemispheric asymmetry of reaction time is manifested: the left hemisphere only responds differently to direct visual stimulation and to that mediated through the contralateral hemisphere.

In healthy adult subjects recognition was studied of geometrical figures presented unilaterally, and of separate letters presented unilaterally and dichoptically to the right and left visual fields. At near-threshold exposition, separate letters are better recognized in the right visual field, than in the left one, regardless of the method of presentation. There is no asymmetry in recognition of geometrical figures. In conditions of backward masking asymmetry of perception of separate letters is likewise observed, but they are better recognized in the left visual field. This suggests that the perception time of separate letters is shorter when they are addressed "directly" to the right hemisphere.