Improved memory functioning and frontal lobe maturation between childhood and adolescence: A structural MRI study

Previous studies conducted by our group have provided evidence for age-rela ted reductions in cortical thickness in dorsal frontal and parietal regions between childhood and adulthood, and gray matter volume increases of mesia l temporal and anterior diencephalic structures. The purpose of this study was to describe neurobehavioral correlates of these brain maturational chan ges using morphometric analyses of brain magnetic resonance images (MRI) an d two tests of cognitive abilities. Participants were 35 normal children ro ughly stratified by age (7 to 16 years) and sex (20 boys and 15 girls) and frontal and mesial temporal regions were anatomically defined in each subje cts' MRI data. The California Verbal Learning Test-Children's Version and t he Rey-Osterrieth Complex Figure test were used as measures of verbal and v isuospatial memory and organizational abilities. Analyses designed to show regionally specific relationships between the brain and behavioral measures revealed interesting results. Specifically, frontal lobe gray matter thinn ing was more strongly predictive of delayed verbal memory functioning than was the mesial temporal lobe gray matter volume, and this relationship did not appear to be mediated by factors indexed in chronological age. Similar, but less regionally specific relationships were observed for measures of v isuospatial memory abilities and frontal lobe maturation. Functional imagin g studies in the literature consistently report activation in frontal regio ns in adults during retrieval tasks. The relationship between frontal lobe maturation and delayed recall observed here may be reflective of the childr en's development towards the more adult-like frontal robe function revealed in the functional imaging studies.