Structural and functional MRI studies of patients with post-stroke language
deficits have contributed substantially to our understanding of how
cognitive-behavioral impairments relate to the location of structural damage
and to the activation of surviving brain regions during language processing,
respectively. However, very little is known about how inter-patient variability
in language task activation relates to variability in the structures affected
by stroke. Here, we used parallel independent component analysis (pICA) to
characterize links between patterns of structural damage and patterns of
functional MRI activation during semantic decisions. The pICA analysis revealed
a significant association between a lesion component featuring damage to left
posterior temporo-parietal cortex and the underlying deep white matter and an
fMRI component featuring (1) heightened activation in a primarily right
hemispheric network of frontal, temporal, and parietal regions, and (2) reduced
activation in areas associated with the semantic network activated by healthy
controls. Stronger loading parameters on both the lesion and fMRI activation
components were associated with poorer language test performance. Fiber
tracking suggests that lesions affecting the left posterior temporo-parietal
cortex and deep white matter may lead to the simultaneous disruption of
multiple long-range structural pathways connecting distal language areas.
Damage to the left posterior temporo-parietal cortex and underlying white
matter may (1) impede the language task-driven recruitment of canonical left
hemispheric language and other areas (e.g. the right anterior temporal lobe and
default mode regions) that likely support residual language function after
stroke, and (2) lead to the compensatory recruitment of right hemispheric
fronto-temporo-parietal networks for tasks requiring semantic processing.
