Children who are adept at any one of the three academic ‘R's (reading, writing and arithmetic) tend to be good at the others, and grow into adults who are similarly skilled at diverse intellectually demanding activities1,2,3. Determining the neuroanatomical correlates of this relatively stable individual trait of general intelligence has proved difficult, particularly in the rapidly developing brains of children and adolescents. Here we demonstrate that the trajectory of change in the thickness of the cerebral cortex, rather than cortical thickness itself, is most closely related to level of intelligence. Using a longitudinal design, we find a marked developmental shift from a predominantly negative correlation between intelligence and cortical thickness in early childhood to a positive correlation in late childhood and beyond. Additionally, level of intelligence is associated with the trajectory of cortical development, primarily in frontal regions implicated in the maturation of intelligent activity4,5. More intelligent children demonstrate a particularly plastic cortex, with an initial accelerated and prolonged phase of cortical increase, which yields to equally vigorous cortical thinning by early adolescence. This study indicates that the neuroanatomical expression of intelligence in children is dynamic.
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This research was supported by the Intramural Research Program of the National Institutes of Health. We acknowledge the statistical advice of G. Chen and technical assistance from T. Nugent III. The authors thank the children who participated in the study and their families. Author Contributions P.S. designed and wrote the study with J.R. and J.G., and conducted neuroimaging analyses. J.G. and J.R. directed the project. D.G. conducted longitudinal analyses. L.C. was data manager, and R.L. and N.G. advised on interpretation and analysis. J.L. and A.E. developed cortical thickness analytic tools and J.L. developed software for longitudinal neuroimaging analyses.
This file contains Supplementary Figure 1 (Interaction between age terms and IQ), Supplementary Table 1 (Pearsons’s correlations between IQ and cortical thickness for each cortical region.), Supplementary Table 2 (Demographic and neuroimaging details of subjects), Supplementary Tables 1 and 2 and Supplementary Methods. This file also contains additional references.