ABSTRACT
Future research that examines the nature of these synaptic processes in vivo through the pubertal period would seem to be crucial to refining our understanding of when maturation of the PFC is achieved. For example, Paus et al. (1999) measured the structural maturation of white matter density in fibre tracts that constitute corticocortical and frontostriatal pathways in a large sample of children and adolescents. Several age-related changes were found. In particular, the pathways subserving speech and motor functions on the left side (the side that was presumably dominant for language ability in the majority of individuals tested) were not mature until late adolescence. Similar work, using diffusion tensor magnetic resonance (MR) imaging, suggests that myelination in the frontal lobe is less wellestablished in prepubescent children than in adults (Klinberg et al., 1999). More recently, a correspondence between cortical grey matter density reductions and increased density of white matter tracts has been reported (Sowell et al., 2001).
