ABSTRACT
Principal components analysis of 56 time series of mean EEG coherence from all brain regions of 224 girls and 284 boys reveals no commonality in regional patterns of cerebral cortex growth from birth to age 16 years. Coherence time series are oscillating waves that represent change over time in EEG wave similarity at two spatially separated electrode sites. Coherence oscillations are thought to mirror the increasing complexity of gray matter structures, particularly overproduction and pruning of synapses at sites compared (local networks). The 56 local networks examined unfold in cycles of growth and pruning that are sexually dimorphic in time, rate, amplitude and flexibility. Bifurcations occur in all local networks around ages 6 and 11 years leading to a partitioning of the first 16 years of postnatal development into early, middle and late periods. It is hypothesized that the bifurcations are points of structural limitation orchestrated by the DNA to shift developmental focus in each sex in preparation for the next life cycle stage. The 11 regional networks determined for each sex represent in-phase growth that accounts for 95 percent of variance in local networks, represents all brain regions in topographically different groupings and has complementary regional networks that reach the adult stage or are retained at the juvenile stage. Models for quantitative and qualitative differences in the sexes’ complementary signatures are discussed.
