Working memory treatment in aphasia: A theoretical and quantitative review

Working memory (WM) is a frequent and long-lasting deficit in patients with aphasia. Progress has been made in our understanding of the nature of WM impairment, by considering deficits at the level of maintenance of item and serial order information (short-term memory), deficits at the level of attentional control, and their complex interactions with language impairment. However, WM treatment studies in aphasic patients remain scarce. This theoretical and quantitative review of 15 single-case treatment studies (24 patients) reveals that WM treatment in aphasic patients is associated with robust near transfer effects and smaller far transfer effects. WM treatment can also raise verbal WM capacity to normal range performance levels. The specificity of WM treatment is more difficult to establish as control tasks/treatments are associated with treatment effects of comparable size as far transfer effects. Existing treatments cover phonological maintenance and control of attention components of WM but do not target difficulties at the level of item interference or serial order processing. In order to improve the specificity of WM treatments, future studies should define WM impairment and treatment targets in a more precise and theoretically informed manner. Also, although the vast majority of reviewed studies meet minimal methodological requirements for single case experimental designs, the use of a larger number of baseline, treatment and control measures is recommended. Finally, publication of treatment studies with negative outcomes should be encouraged as it is currently difficult to estimate the impact of publication bias on observed treatment effects.