The contribution of working memory to language comprehension: differential effect of aphasia type

Background: Experimental studies of short-term memory and working memory (WM) in aphasia fail to discriminate cognitive impairments of different aphasia types—non-fluent, Broca-type aphasia and fluent, Wernicke-type aphasia. However, based on the varying fundamental features of these two aphasia syndromes, the potentially different underlying mechanisms of impairment and scant preliminary evidence of varying cognitive deficits, a differential relationship between cognitive function and language processing in these two groups can be predicted.

Aims: The current study investigates the hypothesis concerning the differential impact of cognitive impairments in individuals with fluent versus non-fluent aphasia types.

Methods & Procedures: Participants with fluent (n = 19) and non-fluent (n = 16) aphasia and participants without brain damage (n = 36) were presented with an eye-tracking WM task. Additionally, individuals with aphasia completed two language comprehension tasks.

Outcomes & Results: Results revealed significant decrease in WM capacity in individuals with aphasia compared with participants without brain damage. The two aphasia groups performed similarly on the WM and language tasks. Furthermore, for participants with non-fluent aphasia, it was revealed that WM makes a significant contribution to language comprehension, while for fluent individuals this relationship was not significant.

Conclusions: Overall, the present data support the claim that there are cognitive deficits in aphasia and that these cognitive deficits tend to exacerbate the language impairments of persons with non-fluent aphasia types. The results are discussed in the context of varying mechanisms of impairment in different types of aphasia. The present findings have important implications both for the assessment and the treatment of individuals with aphasia and for understanding the nature of aphasia.