Influence of linguistic context and working memory on auditory comprehension in young and older adults with aphasia

Abstract

The purpose of the current investigation was to examine the influence of linguistic context on auditory comprehension in adults with aphasia, explore effects of the explanatory variables of age, working memory (WM), aphasia severity, and auditory comprehension relative to linguistic contextual influences, and investigate relationships among these explanatory variables. Eight young (<60) and eight older (>60) individuals with aphasia as the result of a left hemisphere cerebrovascular accident (CVA) participated in the investigation. The participants underwent pre-experimental testing, including two subtests of the Boston Diagnostic Aphasia Examination-III to confirm presence of auditory comprehension impairment as well as ability to perform the experimental tasks. The Western Aphasia Battery-Revised also was administered to determine the presence and severity of aphasia. The participants were administered a series of experimental tasks, including listening span to measure WM capacity, modified Token Test to measure auditory comprehension, and a linguistic context task to examine the influence of predictive and non-predictive contexts on auditory comprehension of passive and active sentences. Results indicated that age did not appear to influence WM, aphasia severity, and auditory comprehension skills in this group of aphasic individuals. Thus, the persons with aphasia (PWA) had reduced WM capacity, regardless of age. However, decreased severity of aphasia was highly related to both increased WM capacity and auditory comprehension skills; that is, WM capacity as well as auditory comprehension increased as severity of aphasia decreased. Moreover, a strong relationship was observed between WM and auditory comprehension, indicating that auditory comprehension increased with increasing WM. Non-predictive context facilitated comprehension of active sentences more than predictive context. Predictive context may have had an adverse influence on comprehension of active sentences, as the PWA may have "lost interest" as well as experienced decreased attention when they heard target sentences containing "old" information that was consistent and possibly repetitious of preceding linguistic context. Non-predictive context facilitated comprehension of active sentences because participants were presented with novel information that was not conveyed in target sentences. However, predictive context was more beneficial than non-predictive context in the comprehension of passive sentences. The PWA had difficulty with passive sentences possibly due to syntactic complexity and semantic reversibility of the sentence contexts. Predictive context facilitated comprehension of the passive sentences because it provided semantic constraints and made one interpretation of target sentences more plausible than the other. In contrast, the non-predictive context simply familiarized the participants with the lexical items of passive sentences; it did not provide the semantically supportive framework, thus making it more difficult to determine which interpretation of the passive sentences was more plausible. This latter result is a robust finding that is consistent with previous research and continues to require further exploration relative to its use in language treatment in aphasia.