Structural correlates of cognitive domains in normal aging with diffusion tensor imaging.

The involvement of brain structures in specific cognitive functions is not straightforward. In order to characterize the brain micro-structural correlates of cognitive domains, 52 healthy subjects, age 25-82 years, completed a computerized neuropsychological battery and were scanned using magnetic resonance diffusion tensor imaging. Factor analysis of 44 different cognitive scores was performed, isolating three cognitive domains-executive function, information processing speed and memory. Partial correlation was conducted between DTI parameters and each of the three cognitive domains controlling for age and motor function. Regions showing significant correlations with cognitive domains are domain-specific and are consistent with previous knowledge. While executive function was correlated with diffusion tensor imaging (DTI) parameters in frontal white matter and in the superior longitudinal fasciculus, information processing speed was correlated with DTI parameters in the cingulum, corona radiata, inferior longitudinal fasciculus, parietal white matter and in the thalamus. Memory performance was correlated with DTI measures in temporal and frontal gray matter and white matter regions, including the cingulate cortex and the parahippocampus. Thus, inter-subject variability in cognitive performance and tissue morphology, as expressed by diffusion tensor magnetic resonance imaging, can be used to relate tissue microstructure with cognitive performance and to provide information to corroborate other functional localization techniques.