The availability of a large cohort of children studied longitudinally across childhood and adolescence enabled the examination of regional cortical trajectories in relation to the intelligence quotient (IQ). Recently, Shaw et al. (Shaw et al., 2006) examined the NIMH (National Institute of Mental Health) pediatric longitudinal data set for anatomic brain development in relation to IQ. Developmental trajectories for total and regional brain cortical thickness were examined in relation to IQ (measured at time of initial scan) for 307 children (the majority of whom had prospective repeated neuroanatomic scans) aged 4-26 yrs, as shown in Figure 2. At younger ages, the relationship between cortical thickness and IQ was relatively broad but approached the more circumscribed frontal lobe regions in later adolescence, suggesting the increasingly localized dependence of GM thickness on cognitive function with age. The contrast in trajectories across IQ groups, however, was particularly interesting with more intelligent children demonstrating a particularly plastic cortex with an initial accelerated and prolonged phase of cortical increase followed by a particularly vigorous phase of cortical thinning suggesting a highly plastic response in the brain.
