Thalamic volume and thalamo-cortical white matter tracts correlate with motor and verbal memory performance.

Cognitive testing and diffusion tensor imaging data from 121 normal subjects were combined to investigate the relationship between thalamic connectivity and cognitive performance. Thalamic regions were segmented based on their cortical connectivity, and regions for both ipsilateral and contralateral thalamocortical connections were identified. White matter tracts corresponding to these regions were identified and the mean fractional anisotropy, and axial and radial diffusivities within each tract were measured. Motor task performance correlated with radial diffusivity in the dominant thalamo-precentral tract. Verbal memory corresponded with the thalamic volume connected to the left temporal lobe. These data support the use of diffusion tractography to identify functionally important regions within the thalamus. Our findings provide the first robust correlation between thalamic volumes and tract characteristics with cognitive performance data in normal subjects.