Age-related Trends in Functional Organization of Cortical Parts of Regulatory Brain Systems in Adolescents: an Analysis of Resting-State Networks in the EEG Source Space

Abstract

Age-related trends in the strength of functional and effective connectivity between key cortical structures that belong to the three most important resting-state neural networks: the default mode network (DMN), the key event detection network (salience network, SN) and the central executive network (CEN) were investigated in adolescents of both sexes. The study involved 34 adolescents of the younger age group: 11–13 years old (12.61 ± 0.75 years, 13 girls and 21 boys) and 54 adolescents of the older group: 14–16 years old (15.00 ± 0.75 years, 20 girls and 34 boys). Frequency-specific estimates of the strength of functional and effective connectivity between the nodes of DMN, SN and CEN were computed in six frequency bands θ (4–7 Hz), α1 (7.5–9.5 Hz), α2 (10–13 Hz), β1 (14–18 Hz), β2 (20–27 Hz) and γ (30–40 Hz) using the vector autoregressive modeling of cortical sources of EEG registered in the resting condition. The analysis of functional connectivity revealed age differences in the θ frequency range, in which the strength of connections between the nodes of all networks in the younger age group was higher than in the older group. Besides, sex-related differences were found in the beta-2 and gamma ranges: the connections between the nodes of DMN were stronger for girls than for boys. The analysis of effective connectivity (directed influences) revealed a significant effect of age in all frequency ranges for the CEN and DMN resting-state networks; for SN, this effect was significant in all but the beta-2 and gamma ranges. The most pronounced age-related changes were found for bottom-up connections directed from more caudal to more frontal areas in CEN and DMN, and in the younger age group, the strength of effective connections was greater than in the older one. The effect of sex on the strength of effective connections was limited mainly to the younger group and manifested itself in stronger DMN and CEN connectivity in girls (as compared with boys) .