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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.

Prepulse modification of acoustic startle reaction (ASR) was studied in patients with schizophrenia and healthy controls according to the protocol recommended by the Consortium on the genetics of schizophrenia. Patients displayed the reduced ASR magnitude of prepulse inhibition (PPI) and increased startle latency prepulse facilitation (PPF) at 60 ms lead interval. The ASR amplitude PPF at 2500 ms lead interval was also impaired in patients. Effects of the recent head trauma and psychoactive drug experience on the ASR prepulse modification were different in patients and controls. The high baseline amplitude and short ASR latency in patients were correlated with the excitation level measured with the PANSS (item P4) whereas the PPF reduction was correlated with the high total score on the PANSS positive subscale. These results suggest the possibility of using ASR prepulse modification in clinical neurophysiology.

Saccades and slow pre-saccadic potentials were investigated in 12 volunteered test-subjects (7 subjects with the leading right eye (RE-group) and 5 subjects with the leading left eye (LE-group) before and after 6-d DI experiment. Visual stimulation was provided with 3 LEDs one of which was located centrally in the field of vision and the other two - 10 degrees left and right along the horizontal axis. The subjects performed the test for antisaccades requiring to produce saccades toward a point symmetrical to displayed stimulus. EEG (monopolar in 19 standard leads) and electrooculogram were registered. Peripheral stimulus activation served as a trigger for backward averaging as a method to obtain slow pre-saccadic potentials (PSPs). Testing before immersion did not reveal any noteworthy differences in saccades produced by the members of both groups. At the same time, amplitude of pre-saccadic negativity (PSN) in LE-group was lower, especially in the frontal region of head, and distinguished by apparent asymmetry throughout the period of analysis. In immersion, latent saccades and percentage of erroneous reactions did not change in the RE-group but increased in the LE-group. Both groups reduced the PSN amplitudes shifting PSN to the right cerebral hemisphere; differences between the groups were masked by immersion. The RE-group was marked by a reliable decline of the PSN amplitude in the frontal leads due to, probably, sensory disintegration and reduced tonic afferentation in immersion. In the LE-group, maximum PSN amplitude was registered in the central region of head equally before and during immersion.

Fifty-eight male adolescents aged 15-17 years have been divided into 3 groups: 31 patients with mental infantilism syndrome were included in the study group, 14 with organic brain disorders--in the comparison group and 13 psychiatrically and neurologically normal subjects--in the control group. EEG was recorded from 12 leads monopolarly at rest, during hemisphere-specific cognitive tasks performance and exposure to aversive sound stimulation. Two-Hz wide EEG spectral ranges--A, theta1, theta2, alpha1 and alpha2--were analyzed. Only in the study group, there were decreased values of alpha2 spectral power (SP) and reduced reactivity to functional tests and insufficient lateral differentiation of the reactions during the cognitive tasks performance. Maximal deviation of the SP reactivity indices as compared to the comparison group was found in alpha2 range. The disturbances obtained indicate the delay of brain maturation and retardation in formation of specific neural networks. The results of the study demonstrate that indices of alpha2 SP may be considered as objective criteria of delayed mental maturation.

Antiorthostaic hypokinesia (AOHK) was found to entail a considerable diminishing of the control system's precision abilities. In the first 14-30 days of the AOHK (the 1st stage), variability of interimpike intervals (ISI) was sharply increased as well as the degree of synchronisation of the motor units' (MU) activity; starting from the 30th day (the 2nd stage), a regular diminishing of the ISI occurred and the MU synchronisation disappeared. The data obtained suggest the different nature of the precision disorders during the 1st and the 2nd stages of the AOHK: a reflex responses to support unloading and the atrophic processes in the muscles, respectively.

The effect of immersion hypokinesia on the precision of programme-type voluntary movements was investigated using standard test movements and quantitative analytical methods. The exposure did not cause disorders in the programme mechanisms but reduced significantly the precision range of the motor control system. The loss of precision was at its maximum (by 100% and over) on immersion day 3. The universality and consistency of the above changes indicated their close association with the specific exposure while the fast rate of their development suggested their reflex nature.

Ten test subjects were exposed to water immersion for 3 days. Extraterritorial potentials of low and high threshold motor units (LMU and HMU) of m. biceps brachii were measured using a specially designed multielectrode and an electromyograph. The results revealed substantial changes in LMUs. A significant decrease in the propagation rate of muscle potentials was observed in 9 out of 10 test subjects. The average propagation velocity of LMU potentials was 4.93 +/- 0.16 m/s before exposure, 4.12 +/- 0.07 m/s after a day of immersion and 4.29 +/- 0.09 m/s after three days of immersion, the mean decrease being 20% and 15%, respectively. The total duration of LMU potentials increased significantly during immersion, the increase making 17.5% after a day of immersion and 13% after three days of immersion. The total depolarized zone length diminished by 1.65 mm after a day of immersion and by 1.29 mm after three days of immersion. Conversely, this exposure produced no significant changes in HMU potentials. It can be assumed that the major cause of changes in LMU potentials is reduced muscle activity.

During 3-day immersion hypokinesia stimulation muscle potentials and averaged potentials of total EMG of m. biceps brachii were investigated in six test subjects. Stimulation potentials were obtained by exciting n. cutaneous with a train of square impulses. Potentials were recorded using a combined multi + electrode. Averaged potentials of total EMG were recorded by means of the same electrode. The propagation rate of the potentials, duration of their negative and end-positive phases as well as the length of their negative phase in space were measured. In addition, vector-electromyographic images of the potentials were recorded. After immersion hypokinesia the propagation rate decreased significantly, the duration of the end-positive phase increased and the length of the depolarized zone of potentials in space shortened. The decrease of the rate of propagation of stimulation potentials was 28% and that of averaged potentials of total EMG was 31% per group. These changes developed rapidly enough, indicating shifts in the properties of potentials of action of myofibers during immersion. Factors responsible for these changes are discussed.