[FREQUENCY-TEMPORAL STRUCTURE OF HUMAN ELECTROENCEPHALOGRAM IN THE CONDITION OF ARTIFICIAL HYPOGRAVITY: DRY IMMERSION MODEL].

Frequency-temporal electroencephalogram (EEG) reactions to hypogravity were studied in 7 male subjects at the age of 20 to 27 years. The experiment was conducted using dry immersion (DI) as the best known method of simulating the space microgravity effects on the Earth. This hypogravity model reproduces hypokinesia, i.e. the weight-bearing and mechanic load removal, which is typical of microgravity. EEG was recorded by Neuroscan-2 (Compumedics) before the experiment (baseline data) and at the end of day 2 in DI. Comparative analysis of the EEG frequency-temporal structure was performed with the use of 2 techniques: Fourier transform and modified wavelet analysis. The Fourier transform elicited that after 2 days in DI the main shifts occurring to the EEG spectral composition are a decline in the alpha power and a slight though reliable growth of theta power. Similar frequency shifts were detected in the same records analyzed using the wavelet transform. According to wavelet analysis, during DI shifts in EEG frequency spectrum are accompanied by frequency desorganization of the EEG dominant rhythm and gross impairment of total stability of the electrical activity with time. Wavelet transform provides an opportunity to quantify changes in the frequency-temporal structure of the electrical activity of the brain. Quantitative evidence of frequency desorganization and temporal instability of EEG wavelet spectrograms may be the key to the understanding of mechanisms that drive functional disorders in the brain cortex in the conditions of hypogravity.

[Phase-locked alpha oscillations evoked by illusory contour perception in normal and autistic preschool boys].

We examined temporal dynamics of EEG phase-locked alpha oscillations during perception of illusory (Kanizsa square) and non-illusory images in boys with autism and age-matched typically developing boys. In typically developing boys the illusory contour (IC) as compared to the control stimulus provoked an increased alpha response at the parietal scalp areas. This IC effect demonstrated continuity within the time window of 133-267 ms after the stimulus onset. Although boys with autism did not display this effect at the group level, part of the sample showed an atypical two-stage pattern of illusory contour effect. The first early stage of IC effect (50-133 ms) was pronounced at the midline occipital electrode localized in the vicinity of the primary visual cortex. The localization and the early onset time suggest that this early IC effect is related to abnormally enhanced "low-level" locally-oriented processes of contour completion in autism. The second stage of IC effect (267-400 ms) was observed at the left parietal region only, and was delayed comparatively to that in healthy boys, suggesting the deficit of "intermediate" processes of perceptual grouping linked to the higher-order visual areas.

[Optimization of counting process of dopaminergic neurons in substantia nigra of parkinsonian mice].

Parkinson's disease (PD) results from degeneration of dopaminergic (DA-ergic) neurons of sunstantia nigra pars compacta (SNc). In experimental studies, this condition is modelled by administration of neurotoxin's precursor 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP). The followed degeneration of DA-ergic neurons is estimated by cell counting. Cell counting with serial sections is exceedingly hard and expensive. Therefore this method is not used extensively in spite of its high precision. Widely known Konigsmark's formula (KF) allows not to count cells in all serial section, but only in sections selected at regular interval. However, its precision decreases with increasing the interval and other parameters. In given work we have developed mathematical method of approximation (MA) by improving of KF. MA allows reducing the time and chemical products expenses for processing and analysis of the material with maintenance of necessary counting precision. Two groups of C56/BL mice were used in this study. The first group received MPTP in a dose of 8 mg/kg with 1 week interval and showed 20% decrease in DA-ergic neurons in SNc. The second group received MPTP in a dose of 12 mg/kg four times with 2-h interval and showed 40 % decrease in DA-ergic neurons in SNc. Degeneration took place mostly in the middle part of SNc within rostra-caudal direction and led to rise of sharp differences in the number of neurons from section to section. These differences substantially decreased precision of FK (6 % error with counting in every 5th section), whereas precision of MA was sufficiently good (4% error with counting in every 7th section). Thus, we have developed MA, that allows us to decrease expenses of the time and chemicals for estimation of DA-ergic cells number in SNc of parkinsonian mice.

[Alpha oscillations of human brain elicited by illusory contour perception].

We examined the changes in the phase-locked and total alpha oscillations of EEG during perception of illusory (Kanizsa square) and non-illusory images in 16 healthy adults. We applied a wavelet-based time-frequency analysis to compute alpha band power, statistical evaluation was performed using repeated-measures ANOVA and the non-parametric multi-way analysis. Results showed that both stimuli provoked an initial increase of total alpha power emerging not later than in 100 ms after the stimulus onset. The increase was caused by the phase-locked alpha response, and the illusory contour was systematically followed by a higher level of alpha power than the non-illusory one. Further suppression of total alpha power occurred within the time window of 200-500 ms after the stimulus onset and did not depend on the stimulus type. Both stages of the total alpha response were more prominent over the parieto-occipito-temporal scalp areas. We hypothesize that the first stage of alpha response is related to the modulation of the activity of neural circuits participating in processing of a coherent pattern whereas a later suppression of total alpha power links to the orienting processes.

[Fasting diet therapy in gastrointestinal tract diseases].

The article is devoted to an effective not medicamentous method of therapy--to the medical starvation. Indications and contra-indications to carrying out of medical starvation are given. Own results of use of medical starvation are resulted at diseases of bodies of digestion. Practical recommendations on applications of medical starvation for patients with diseases of bodies of a gastroenteric path are submitted.