Differentiation of electroencephalographic waking rhythms during the first year of life

The method of broad-band authomatic filtering of 20-sec EEG epochs for frontal, central, temporal and occipital areas of both hemispheres was used. The obtained integrated value of the amplitude of the delta-, theta-, alpha- and beta 1-rhythms was studied with respect to: (a) the age-determined course of the differentiation between the values of the different rhythms in healthy infants during wakeful periods with open eyes; and (b) formation of topographic specificities of these rhythms. The differentiation of the rhythms was age-dependent. The existence of an intricate process of differentiation between delta and theta, theta and alpha, as well as alpha and beta, was proved. When slow rhythms dominated significantly, there was heterochronous differentiation according to regions and formation of an age-dependent topographic constellation of values. The changes in theta and alpha were more intensive and affected almost all regions in both hemispheres, while for beta they were not only less pronounced, but they also proceeded in a different way in the two hemispheres. Interhemispheric asymmetry was found only for beta 1 and was localized in the temporal regions.