Biomedical subjects
Publications and source records attributed to R I Machinskaia.
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Degree of manifestation and synchronization of rhythmic alpha-range components in various cortical areas was studied in healthy adult subjects in conditions of controlled computer experiment by spectral-correlation method of EEG analysis during directed attention previous to discrimination of tactile, auditory and visual stimuli. The obtained results show that in preparation for discrimination of heteromodal stimuli, specific reconstructions take place of alpha-range electrical activity determined by signal modality. These changes are expressed in a local increase of the degree of synchronization of alpha oscillations in those projection and associative brain areas which are connected with the analysis of the given stimuli. Functional significance of these reconstructions is seen in the fact that they are significantly more expressed at correct recognition. A hypothesis is suggested about participation of the alpha-range in neurophysiological mechanisms of directed attention.
Structuration of medical information is performed on three levels: structuration of the specialist's knowledge with resultant singling out key questions--blocks required for diagnosis in the given field; structuration of signs within the space of the blocks; identification of diagnostic syndromes basing on their signs analysis adjusted to resolving diagnostic tasks. The results of the method application in neuropathology are outlined.
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EEG characteristics of brain organization of selective attention were studied in children (n = 10, 9 years old) during task expectancy with special reference to hemisphere specialization. Children had to distinguish lateralized signals according to their duration. Warning stimulus pointed to the modality of the task (tactile, auditory, visual). Intra-hemispheric alpha-coherence was evaluated in the prestimulus period with the following statistical analysis of the individual data. The main distinctions of the brain functional organization during expectancy between children and adults consisted in less pronounced selectivity of EEG changes in the left hemisphere and in existence of modal specificity in the right hemisphere in children as compared to adults. Thus, the functional specialization of the hemispheres in children is not yet completely developed. Brain hemispheres of children partly share functions rather than complement each other.
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Intrahemispheric functional organization was studied during a task expectancy period with special reference to attention mechanisms. The estimation of coherence of functionally identical rhythmic EEG components was made to characterize the intracortical integration. Several factors influencing the possibility to make an adequate prognosis and to realize it were varied. Different types of the task were used. Subjects of different age (7, 9-10 years, young adults) and children of the same age differing by the brain maturity level were under study. It was shown that all factors studied have certain influence on the brain organization underlying the task preceding attention. Clear age differences as well as the lag between the possibility to formation and realization the prognosis in children were observed. Alternative "strategies" used in different ages to facilitate the task performance were analysed; underlying mechanisms were discussed.
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Simultaneous consideration of EEG, neurological, and imaging data obtained with sequelae of ischemic stroke during rehabilitation allowed us to verify the organic nature of some EEG phenomena. It was shown that stroke-induced impaired circulation in the area of the middle brain artery gave rise to deviant local cortical electrical activity (EA) in the form of polymorphic theta and delta waves or groups of theta waves. The character of such activity depended on the lesion size and extent of blood supply deficit in the damaged area. Decrease in the lesion size and restoration of blood supply during rehabilitation were accompanied by changes in the local deviant EA: the polymorphic slow-wave activity was replaced by single alpha and theta sharp waves. The restoration of motor functions was less successful in cases with the local deviant EA localized in the caudal part of the cortex.