The role of executive control in post-stroke aphasia treatment

ABSTRACT

Executive control (EC) ability is increasingly emerging as an important predictor of post-stroke aphasia recovery. This study examined whether EC predicted immediate treatment gains, treatment maintenance and generalization after naming therapy in ten adults with mild to severe chronic post-stroke aphasia. Performance on multiple EC tasks allowed for the creation of composite scores for common EC, and the EC processes of shifting, inhibition and working memory (WM) updating. Participants were treated three times a week for five weeks with a phonological naming therapy; difference scores in naming accuracy of treated and untreated words (assessed pre, post, four- and eight-weeks after therapy) served as the primary outcome measures. Results from simple and multiple linear regressions indicate that individuals with better shifting and WM updating abilities demonstrated better maintenance of treated words at four-week follow-up, and those with better common EC demonstrated better maintenance of treated words at both four- and eight-week follow-ups. Better shifting ability also predicted better generalization to untreated words post-therapy. Measures of EC were not indicative of improvements on treated words immediately post-treatment, nor of generalization to untreated words at follow-up. Findings suggest that immediate treatment gains, maintenance and generalization may be supported by different underlying mechanisms.

KEYWORDS:

• Aphasia
• anomia
• executive control
• executive functions
• treatment

Acknowledgments

The authors would like to thank the participants and their families, as well as our referral sites across the Greater Toronto Area (the Aphasia Institute, and the March of Dimes Aphasia and Communication Disabilities Program). The authors would also like to thank Drs. Randi Martin, Corrine Allen, Nadine Martin and Lynne Hasher for generously sharing their experimental tasks for this study. Finally, the authors would like to acknowledge the following members of the Language Sciences Laboratory for assistance with data collection and scoring: Laura Laird, Fiona Hobler, Claire Dreyfuss and So Yeun Kim.

Disclosure statement

No potential conflict of interest was reported by the authors.

Notes

1 We created a common EC composite score which included inhibition RT data in addition to inhibition accuracy, shifting and WM updating measures. Main regression findings show the same patterns when inhibition RT measures were added to the common EC composite score. However, in order to give equal weight to each EC process of interest, we opted to use the common EC composite score which did not include measures of inhibition RT.

2 Three participants (P1, P2 & P3) were part of a concurrent study and received the PCA treatment protocol on slightly different schedules: P2 and P3 (3 sessions per day, 4 days a week for 2.5 weeks); P1 (1 session per day, 3 days a week for 10 weeks). All participants received a total of 30 sessions of therapy. No differences were noted in average session duration, total treatment hours, or in treatment performance as a function of treatment schedule, thus these participants were included in the present analysis.

Additional information

Funding

This work was supported by the Heart and Stroke Foundation of Canada [grant #7308, #7015; awarded to E. Rochon and C. Leonard], and by the HSF Canadian Partnership for Stroke Recovery (CPSR) [scholarship awared to T. Simic]. Funding sponsors had no further involvement in the study.