Shared White-Matter Tracts Underlying Language and Executive Control

Language and executive control are theorised to be related cognitive domains, but their shared underlying neural substrate remains unclear. Phonological processing and criterion-setting are both purported to be subserved by the left dorsal white matter tracts. Thus, this study investigated whether lesions of any left dorsal white matter tracts were associated with deficits in both (1) word and sentence repetition, and (2) the trail-making test. Retrospective clinical data from 31 stroke patients at the Azienda University Hospital of Padova were analysed. Within seven days post-stroke, patients underwent cognitive assessments and structural neuroimaging. Lesion maps were drawn in the neuroimages, from which tract disconnection probabilities and disconnectome maps were derived. Poorer repetition performance was significantly moderately-to-strongly correlated with disconnection of the left superior longitudinal fasciculus I, ρ (23) = -.53, p = .007, superior longitudinal fasciculus II, ρ (23) = -.73, p < .001, superior longitudinal fasciculus III, ρ (23) = -.53, p = .007, and the arcuate fasciculus, ρ (28) = -.70, p <.001. Poorer trail-making performance was significantly moderately correlated with disconnection of the left superior longitudinal fasciculus II, ρ (22) = -.45, p = .029. Multivariate support vector regression was used to predict performance on repetition and trail-making based on disconnectome maps. The model was not significant, and therefore it was not possible to localise any particular tract which predicted performance on the cognitive tests. The small sample size notably limited the statistical power and generalizability. Overall, these results suggest that these complex cognitive functions may not be observable without more extensive cognitive assessments and larger sample sizes.