[The functional organization of the cerebral hemispheres during directed attention in children 7 to 8 years old]

Functional organization of brain hemispheres of 15 right-handed 7-8-years-old children was analysed during attention directed to the classification of lateralized auditory and tactile stimuli according to their duration. The subjective task difficulty was equal for all the children. Random presentation of stimuli in series of right and left-side stimulation and visual indication of the forthcoming stimulus modality (warning signal) improved the direction of subject's attention in accordance with the instruction. Monopolar EEGs were recorded from 15 cortical leads in both hemispheres referenced to linked ear lobes. EEG spectral 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 was shown to be absent in children. Local functional integration of cortical regions around the modality-specific areas (T3, T4 for the auditory and C3, C4 for the tactile stimulation) was found in both hemispheres of children in contrast to the only left hemisphere in adults. The diffuse, modality-independent functional organization of adult right hemisphere was not observed in children. The described features of intrahemispheric organization in both groups provide correct decisions thus characterizing the successful alternative strategies. The grounds of revealed age differences, age-dependent mechanisms of functional hemisphere organization, and nonlinear trend of hemispheric specialization development are discussed.