FUNCTIONAL-ORGANIZATION OF BRAIN HEMISPHE RES OF CHILDREN AGED 7-8 YEARS DURING DIRECTED ATTENTION

Functional organization of brain hemispheres of 15 right-handed 7-8 ye ars old children was analysed during attention directed to the classif ication of lateralized auditory and tactile stimuli according to their duration. The subjective task difficulty was equal for all the childr en. Random presentation of stimuli in series of right and left-side st imulation and visual indication of the forthcoming stimulus modality ( warning signal) improved the direction of subject's attention in accor dance with the instruction. Monopolar EEGs were recorded from 15 corti cal leads in both hemispheres referenced to linked ear lobes. EEG spec tral analysis was performed with assessment of spectral power density and coherence of the alpha-range components. The hemisphere dichotomy which had been revealed in adult subjects under the same conditions wa s shown to be absent in children. Local functional integration of cort ical regions around the modality-specific areas (T3, T4 for the audito ry and C3, C4 for the tactile stimulation) was found in both hemiphere s of children in contrast to the only left hemisphere in adults. The d iffuse, modality-independent functional organization of adult right he misphere was not observed in children. The described features of intra hemispheric organization in both groups provide correct decisions thus characterizing the successful alternative strategies. The grounds of revealed age differences, age-dependent mechanisms of functional hemis phere organization, and nonlinear trend of hemispheric specialization development are discussed.