The Role of Fronto-Parietal and Fronto-Striatal Networks in the Development of Working Memory: A Longitudinal Study

The increase in working memory (WM) capacity is an important part of cognitive development during childhood and adolescence. Cross-sectional analyses have associated this development with higher activity, thinner cortex, and white matter maturation in fronto-parie-tal networks. However, there is still a lack of longitudinal data showing the dynamics of this development and the role of subcorti-cal structures. We included 89 individuals, aged 6–25 years, who were scanned 1–3 times at 2-year intervals. Functional magnetic res-onance imaging (fMRI) was used to identify activated areas in superior frontal, intraparietal cortices, and caudate nucleus during performance on a visuo-spatial WM task. Probabilistic tractography determined the anatomical pathways between these regions. In the cross-sectional analysis, WM capacity correlated with activity in frontal and parietal regions, cortical thickness in parietal cortex, and white matter structure [both fractional anisotropy (FA) and white matter volume] of fronto-parietal and fronto-striatal tracts. However, in the longitudinal analysis, FA in white matter tracts and activity in caudate predicted future WM capacity. The results show a dynamic of neural networks underlying WM development in which cortical activity and structure relate to current capacity, while white matter tracts and caudate activity predict future WM capacity