Our previous work suggests that the size of the brain changes little after the age of five years (Giedd et. al. Cerebral Cortex 6:551-560, 1996). Here we seek to evaluate the possibility that, after this age, the human brain continues to grow in a region-specific fashion. T1-weighted MRIs (1.5mm axial slices, TR=24ms, TE=5ms, flip angle=45 ° ) of 113 subjects (4-6yr: 13 boys, 6 girls; 7-9yr: 13b, 9g; 10-12yr: 14b, 13g; 13-15yr: 21b, 10g; 16-18yr: 5b, 9g) were acquired and automatically processed for correction of image-intensity inhomogeneities, linear transformation into standardized stereotaxic space, and non-linear (NL) transformation to match a single "template" volume (FWHM=4mm). The NL transformations represent local differences at each voxel between the subject and template, and are indicators of individual anatomic variability. These transformations were used in voxel-wise multivariate linear regression analysis to identify regions in which age correlated with a local change in X, Y and/or Z vecotrs; the effect of gender was first removed. Hotelling's T ² was employed to evaluate statistical significance of such correlations, with the threshold set at F>12.6 (3,108 d.f., p<0.05, corrected for whole-brain search). Significant correlations were found around both the temporal lobes and ventral aspects of the frontal lobes. Analysis of the X, Y and Z vectors indicates a possible overall growth of the temporal lobes and/or their downward and lateral "movement". Fronto-orbital cortex appears to move upwards, outwards, and forwards. These findings suggest that, in the range between 4 and 18 yrs, the brain continues to change its shape locally. It remains to be determined what underlies such changes in the brain's gross anatomy.

Soc.Neurosci. Abstr. 24:304, 1998