Processing distinct linguistic information types in working memory in aphasia

Abstract

Background: Recent investigations have suggested that adults with aphasia present with a working memory deficit that may contribute to their language‐processing difficulties. Working memory capacity has been conceptualised as a single “resource” pool for attentional, linguistic, and other executive processing—alternatively, it has been suggested that there may be separate working memory abilities for different types of linguistic information. A challenge in this line of research is developing an appropriate measure of working memory ability in adults with aphasia. One candidate measure of working memory ability that may be appropriate for this population is the n‐back task. By manipulating stimulus type, the n‐back task may be appropriate for tapping linguistic‐specific working memory abilities.

Aims: The purposes of this study were (a) to measure working memory ability in adults with aphasia for processing specific types of linguistic information, and (b) to examine whether a relationship exists between participants' performance on working memory and auditory comprehension measures.

Method & Procedures: Nine adults with aphasia participated in the study. Participants completed three n‐back tasks, each tapping different types of linguistic information. They included the PhonoBack (phonological level), SemBack (semantic level), and SynBack (syntactic level). For all tasks, two n‐back levels were administered: a 1‐back and 2‐back. Each level contained 20 target items; accuracy was recorded by stimulus presentation software. The Subject‐relative, Object‐relative, Active, Passive Test of Syntactic Complexity (SOAP) was the syntactic sentence comprehension task administered to all participants.

Outcomes & Results: Participants' performance declined as n‐back task difficulty increased. Overall, participants performed better on the SemBack than PhonoBack and SynBack tasks, but the differences were not statistically significant. Finally, participants who performed poorly on the SynBack also had more difficulty comprehending syntactically complex sentence structures (i.e., passive & object‐relative sentences).

Conclusions: Results indicate that working memory ability for different types of linguistic information can be measured in adults with aphasia. Further, our results add to the growing literature that favours separate working memory abilities for different types of linguistic information view.