Growing together: Dynamic connectivity between developmentally sensitive regions serving verbal working memory in children and adolescents.

The neural network serving verbal working memory processes undergoes dramatic changes during the transition from childhood to adolescence, including changes in cortical thickness, activation levels, connectivity and inherent dynamics. Of all these neural properties, maturational changes in dynamic functional connectivity among developmentally sensitive regions within this network are among the least understood. To address this, we examined 75 typically developing youth (age range 6-14 years), who completed a verbal working memory task during magnetoencephalography (MEG). All MEG data were imaged and the phase-locking value was computed as an index of functional connectivity between regions exhibiting significant relationships with chronological age. Our results suggested developmental differences in functional connectivity during specific phases of working memory processing. During encoding, connectivity increased with age between left prefrontal and inferior parietal, with such age-related increases varying by sex between right frontal and left occipitotemporal regions. During the maintenance period, connectivity increased with age between left occipitotemporal and right posterior parietal areas and decreased with age between left frontal and right occipital cortices. These findings suggest that neural oscillations within regions serving working memory processing, as well as functional connectivity among these regions, are modulated by development during the transition from childhood to adolescence. KEY POINTS: With development from childhood to adolescence, verbal working memory processing becomes increasingly left lateralized in the prefrontal, parietal and temporal cortices. Several electrophysiological studies have shown that alpha oscillations within these brain regions become stronger with increasing chronological age during the transition from childhood to adolescence. Although such oscillatory power differences are well established, age-related changes in functional connectivity among these brain regions is far less understood. Here, we report novel findings suggesting that functional connectivity between developmentally sensitive cortical regions supporting verbal working memory scales with age among visual, language and attention-related brain systems. These results help to refine models of functional neural development supporting verbal working memory ability for future application in both basic research and clinical studies of typical and atypical cognitive development.