Recovery of Verbal Working Memory Depends on Left Hemisphere White Matter Tracts

Researchers propose that the recovery of language function following stroke depends on the recruitment of perilesional regions in the left hemisphere and/or homologous regions in the right hemisphere. Many investigations of recovery focus on changes in gray matter regions, whereas relatively few examine white matter tracts and none address the role of these tracts in the recovery of verbal working memory. The present study addressed these gaps, examining the role of left versus right hemisphere tracts in the longitudinal recovery of phonological and semantic working memory. For 24 individuals with left hemisphere stroke, we assessed working memory performance within 1 week of stroke (acute time point) and at more than 6 months after stroke (chronic time point). To address whether recovery depends on the recruitment of left or right hemisphere tracts, we assessed whether changes in working memory were related to the integrity of five white matter tracts in the left hemisphere which had been implicated previously in verbal working memory and their right hemisphere analogues. Behavioral results showed significant improvement in semantic but not phonological working memory from the acute to chronic time points. Improvements in semantic working memory significantly correlated with tract integrity as measured by functional anisotropy in the left direct segment of the arcuate fasciculus, inferior fronto-occipital fasciculus and inferior longitudinal fasciculus. The results confirm the role of white matter tracts in language recovery and support the involvement of the left rather than right hemisphere in the recovery of semantic working memory.