[The endophenotype concept in the neurophysiological studies of schizophrenia].

The endophenotype concept is considered as theoretical basis for the study of pathobiological mechanisms of schizophrenia and for the development of the complex of instrumental diagnostic methods. The contemporary state of the problem and the most significant results of the study of three neurophysiological schizophrenia endophenotypes are presented in the review: P50 auditory evoked potential suppression, prepulse inhibition of the startle reflex and antisaccade task. The current understanding of the underlying neurophysiological and neurochemical mechanisms is described for each measure. The results of the association studies of neurophysiological endophenotypes with the relevant to schizophrenia genes' polymorphisms are laid down. High degree of independence of the considered endophenotypes is demonstrated. Taking into account the data on relatively low specificity of each endophenotype to schizophrenia compared to other mental disturbances the authors pay special attention to the model of multivariate endophenotype as a scientific and diagnostic tool.

[An experiment in using Sternberg's paradigm in studying cognitive visual functions in man]. / Opyt primeneniia paradigmy Sternberga pri izuchenii kognitivnykh zritel'nykh funktsii u cheloveka.

Sternberg's technique of additive factors was used. Subjects had to define whether the test and the standard stimuli were identical or not by pressing one of two buttons. Reaction time was shorter in the trials with identical stimuli than in the trials with different ones. Three factors were shown to underly the difference. First, the duration of comparison of visual images under the same and different conditions was not equal. Second, there were fewer comparisons in the trials with identical stimuli. Third, the duration of comparison of stimuli and the number of comparisons could affect other stages of perceptual task.

[Changes in the late components of evoked cortical potentials during the human solving of a visual-spatial task]. / Izmeneniia pozdnykh komponentov vyzvannykh korkovykh potentsialov pri reshenii chelovekom zritel'no-prostranstvennoi zadachi.

The ability of mental construction of easily verbalized geometric figures was studied in 20 healthy subjects by means of recording of the evoked potentials of the cerebral cortex. Fragments of geometric figures were presented with the intervals of 80 and 500 ms. To one half of the subjects the stimuli were presented unilaterally (both fragments to one and the same visual field, to the left or to the right one) and to the second half of the subjects--bilaterally (the first fragment--to one visual field and the second one--to the other). It was established that the latency of the wave P300 was shorter and the amplitude--greater at correct decisions of the visual-spatial task than at false ones, both at unilateral and bilateral fragments presentation. At a great interval (500 ms), when the effects of masking became significantly weaker, a predominant activation of the left hemisphere was observed: the latency of the late components was shorter and the amplitude--greater, when the information came "directly" to the left hemisphere. The obtained results testify once more to a great variability, dynamic interhemispheric relations, impossibility of connecting the realization of some functions with one of the hemispheres.

[The effect of masking in the human subject on the solving of a visual-spatial task]. / Vliianie maskirovki u cheloveka na reshenie zritel'no-prostranstvennoi zadachi.

Images of two fragments of regular geometrical figures (square, triangle etc.) have been presented to 58 healthy persons successively with intervals of 20, 80, 120 and 380 ms. The subject must compare these fragments mentally, decide whether they form the standard figure and press a button by the right or left hand according to the instruction. At presentation of both fragments in one visual field, left or right, the number of correct responses is greater when they form the figure. The greater the interstimulus intervals, the greater the number of correct responses to stimuli forming and not forming the standard figure. At presentation of fragments in different visual fields, the number of correct decisions is the same, independently from forming the standard figure. The reaction time is shorter when exposing fragments forming the figure, independently from the way of their presentation; with prolongation of interstimulus intervals the reaction time decreases in all cases. The number of correct decisions is greater and the reaction time is shorter when the stimuli are presented in different visual fields.

[Solution of visuo-spatial tasks during masking]. / Reshenie zritel'no-prostranstvennoi zadachi v usloviiakh maskirovki.

The images of two fragments of simple geometrical figures (square, triangle, etc.) were successively presented to healthy adult subjects in the left and right visual fields with the interval of 20, 80 and 380 ms; the subjects had to compare them mentally and decide whether they formed a geometrical figure. The correctness of reaction was controlled by a computer which lightened on the screen the word "correct" or "error". The number of correct decisions was significantly greater in response to the stimuli, forming a regular figure and increased with the increase of interstimuli interval. At the interval of 120 ms, when no regular figure could be formed from two fragments, the number of correct decisions was greater if the stimuli were presented in the left visual field. The reaction time did not depend on the hemisphere to which information was addressed; it was less in response to the stimuli forming a regular figure, and became shorter with the increase of the interstimuli interval.

[Lateralization of visual perception of letters during reverse masking]. / Lateralizatsiia zritel'nogo vospriiatiia bukvennykh stimulov v usloviiakh obratnoi maskirovki.

Identification by healthy subjects of single letters in conditions of backward masking was studied at lateralized presentation of stimuli. Both at dichoptic and unilateral presentations, the letters are identified better if they are presented in the left visual field, i.e. addressed "directly" to the right hemisphere. It is suggested that the data obtained result from the specificity of hemispheres' cooperation under difficult conditions of visual-spatial stage of information processing.