Deficits in working memory are a critical subset of nonlinguistic impairments in aphasia. Previous studies indicated that individuals with aphasia made more errors on working memory tasks compared to individuals without cognitive or neurological impairments. Also, an association between working memory capacity and general language abilities in people with aphasia was demonstrated. Unfortunately, the study of working memory in aphasia is fraught with methodological limitations, thus reducing validity and generalization of findings. The goal of this current study was to reduce confounds associated with existing tasks and measures by developing working memory span tasks suited for individuals with aphasia and establishing the psychometric properties of associated performance measures.
Participants engaged in four working memory tasks. In the traditional listening span task, participants without aphasia listened to long compound sentences, verified their semantic plausibility, remembered a set of separately presented words, and then recalled them at the end of a sentence set. In the modified listening span task, participants heard sentences, pointed to an image within a multiple-choice display that best matched that sentence, and remembered a set of words for later recall. In the counting span task, participants counted the number of target shapes within each display and remembered the final tally for recall. In the eye-movement working memory task, participants' eye movements were monitored during presentation of verbal and visual stimuli. This was an eye-tracking version of the modified listening span task, with colors and symbols as items to be remembered.
Recall performance on all working memory tasks was significantly correlated. Significant differences in processing and storage scores emerged between participants with and without aphasia. No relationship was observed between storage scores and scores on a standardized aphasia language test. Results highlight a dissociation between working memory capacity and language abilities and underscore the importance of assessing working memory in people with aphasia as a construct distinct from linguistic abilities. Further study of the role of WM in aphasia is important for better understanding of the nonlinguistic aspects of aphasia, developing valid and reliable assessment methods, and providing optimal treatment while taking nonlinguistic factors into account.