Role for memory capacity in sentence comprehension: Evidence from acute stroke

Background: Previous research has suggested that short-term and working memory (WM) resources play a critical role in sentence comprehension, especially when comprehension mechanisms cannot rely on semantics alone. However, few studies have examined this association in participants in acute stroke, before the opportunity for therapy and reorganisation of cognitive functions. Aims: The present study examined the hypothesis that severity of short-term memory (STM) deficit due to acute stroke predicts the severity of impairment in the comprehension of syntactically complex sentences. Furthermore, we examined the association between damage to the short-term and WM network and impaired sentence comprehension, as an association would be predicted by the previous hypothesis. Methods & Procedures: Forty-seven participants with acute stroke and 14 participants with a transient ischemic attack (TIA; the control group) were included in the present study. Participants received a language battery and clinical or research scans within 48 hrs of hospital admittance. The present study focused on the behavioural data from the STM and WM span tasks and a sentence-picture matching comprehension task included in this battery. Using regression analyses, we examined whether short-term and WM measures explained significant variance in sentence comprehension performance. Outcomes & Results: Consistent with prior research, STM explained significant variance in sentence comprehension performance in acute stroke; in contrast, WM accounted for little variance beyond that which was already explained by STM. Furthermore, ischemia that included the short-term/WM network was sufficient to cause sentence comprehension impairments for syntactically complex sentences. Conclusions: The present study suggests that STM resources are an important source of sentence comprehension impairments.