Formation of the functional organization of the cerebral cortex at rest in young schoolchildren varying in the maturity of cerebral regulatory systems: I. Analysis of EEG spectral characteristics in the state of rest

Abstract

Spectral correlation analysis of the EEG was used to study the organization of the rhythmic electrical activity (EA) of the cerebral cortex in normal children aged seven to eight and nine to ten years and children with the two types of functional immaturity of cerebral regulatory systems most common at this age, namely, fronto-thalamic regulatory system immaturity (IFTS) and brainstem nonspecific activation system immaturity (deficiency) (DNA). Statistical comparison (ANOVA) of these groups of children with respect to the absolute and relative α-and ϑ-band spectral powers of the background EEGs of 12 cortical areas showed the specific features of the effects of functional immaturity of regulatory systems at different levels on the cortical rhythmic EA pattern at rest. DNA led to a significant increase in the absolute spectral power of α and ϑ waves recorded in all derivations in both age groups, which indicated a generalized decrease in cortex activation in these children. IFTS caused a significant decrease in the relative strength of α waves and an increase in the strength of ϑ waves. Taking into account the results of ontogenetic studies, this may be regarded as evidence for a relative underdevelopment of cortical rhythm-generating networks. The absolute spectral powers of both α and ϑ waves were decreased in all groups of children by nine to ten years of age, which indicated that nonspecific activation was enhanced in the age interval studied. Significant changes were observed in children with functional immaturity of regulatory systems. In children with DNA, the age-related increase in cortex activation was expressed as a significant increase in the α-rhythm peak frequency. In children with IFTS, by nine to ten years of age, both the absolute and relative strengths of ϑ waves were decreased in most cortical areas studied, which may be regarded as the progressive formation of cortical rhythm-generating mechanisms.