Discourse abilities in post-stroke aphasia: A multi-level analysis of macro and micro-structural discourse properties and their white matter neural correlates

Although it is well established that discourse abilities are often impaired in people with aphasia (PWA), research and assessment methods addressing spoken discourse in Spanish-speaking PWA are limited. Moreover, the white matter underpinnings of discourse production in aphasia are understudied, calling for their comprehensive examination across both macro and micro-structural levels. The present study developed a Spanish main concept (MC) checklist for the Cookie Theft picture description task to assess discourse informativeness abilities in Spanish-speaking PWA. We used this task to evaluate discourse performance in 19 Spanish-speaking PWA relative to 37 neurotypical controls as per macro-structural and micro-structural discourse metrics. The association between discourse performance and aphasia severity as well as brain structural connectivity as per bilateral language-related white matter tract volumes and fractional anisotropy values were investigated in PWA. Our Spanish MC checklist for the Cookie Theft resulted in 7 MCs largely consistent with previous research. We found that PWA performed significantly below the neurotypical controls in most discourse metrics. Aphasia severity was associated with the number of verbs produced in picture description. The volumes of the left Arcuate Fasciculus (posterior segment) and the right Inferior Longitudinal Fasciculus were associated with micro- and macro-structural metrics of discourse performance, respectively. Our findings suggest that white matter structural connectivity in the left and the right hemisphere may differentially support linguistic and functional aspects of discourse ability in chronic aphasia.