Fiber tracking functionally distinct components of the internal capsule

▶ The internal capsule conveys information from primary and supplementary motor areas, frontopontine and thalamic peduncles to brain stem and cerebellar regions, and from thalamus to prefrontal cortex. ▶ Diffusion tensor imaging (DTI) fiber tracking conducted in young and elderly men and women revealed two gradients of age effects: greater age-related degradation of the anterior than posterior and superior than inferior sectors of the internal capsule. ▶ Correlations between microstructural condition of the inferior sector of the internal capsule and tests of selective cognitive and motor functions identified a triple dissociation: greater anterior limb degradation related to poorer set shifting scores, genu degradation related to motor skills, and posterior degradation related to fluency.