White Matter Microstructure Correlates with Memory Performance in Healthy Children: A Diffusion Tensor Imaging Study.

BACKGROUND AND PURPOSE The complex function of memory has been linked to both brain gray and white matter (WM). WM abnormalities are associated with memory impairment in pathological conditions. We investigated whether variation in WM microstructure in healthy children also correlates with memory performance. METHODS Sixty-five 7.5 to 8.5-year-old healthy children had a brain MRI scan using diffusion tensor imaging (DTI). They were also assessed for memory performance using the Children's Memory Scale (CMS). Eight indices that evaluate verbal and visual memory (immediate and delayed) were measured. DTI parameters reflecting WM microstructure, including fractional anisotropy (FA), mean diffusivity (MD), radial diffusivity (RD), and axial diffusivity (AD), were calculated and correlated with memory indices. RESULTS Tract-based spatial statistics analysis showed multiple WM tracts in which DTI parameters correlated with CMS indices. Specifically, FA (a reflection of WM integrity) and RD values (a reflection of myelination) in multiple projecting, association, and commissural WM tracts correlated with verbal delayed index (P < .05, corrected for voxel-wise multiple comparisons). Also, FA values in several WM tracts, including superior longitudinal fasciculus and posterior corona radiata, positively correlated with delayed recognition index (P < .05, corrected). Region of interest analyses showed similar correlations between FA/RD and CMS scores in WM regions involving these tracts and additionally in the cingulum, and detected additional MD-CMS correlations in several regions. CONCLUSIONS Significant correlations between DTI parameter values and CMS indices in multiple WM tracts in healthy children indicate that neuroimaging can sensitively detect brain WM changes associated with variations of memory function, even for that in the normal range.