Role of cognitive control in language deficits in different types of aphasia

ABSTRACT

Background: Although studies show that different facets of cognitive control are impaired in persons with aphasia (PWA), the question how they impact language abilities in different types of aphasia remains open.

Aims: Following the hypothesis that diminished attention contributes to language impairments in aphasia, we predicted that both fluent and non-fluent PWA would perform worse than neurologically intact individuals on verbal and non-verbal cognitive control tasks. Also, testing the view that linguistic disturbances in fluent and non-fluent PWA dissociate, we predicted differential relationships in performance on cognitive control tasks and language impairment.

Methods & Procedures: Fluent PWA (N = 17) and non-fluent PWA (N = 14) were compared to unimpaired speakers (N = 21) on the non-verbal Flanker task tapping domain-general cognitive control, and Stroop task measuring verbal cognitive control, as well as subtests from the Russian version of the Birmingham Cognitive Screen, namely the Auditory Control task tapping verbal cognitive control and the Rule Finding task measuring domain-general cognitive control. All PWA completed picture naming and language comprehension tasks.

Outcomes & Results: All PWA were more impaired on the Stroop and Auditory Control tasks, with no impairment on the non-verbal Flanker task compared to the controls. Non-fluent PWA also performed significantly worse on the Rule Finding that requires forming and updating non-verbal relational representations. Differences between aphasia groups were found on the Auditory Control task only, where non-fluent PWA were more vulnerable to task demands. Correlation analyses found that verbal and non-verbal cognitive control performance was correlated for the non-fluent group, whereas only correlations between verbal cognitive control tasks were significant for the fluent group. For all PWA, non-verbal cognitive control indexed by Flanker interference scores was related to language comprehension, whereas verbal cognitive control was related to picture naming. However, non-verbal relational reasoning as indexed by the Rule Finding task was significantly related to language comprehension in the non-fluent group only.

Conclusions: All PWA had diminished verbal cognitive control. Non-fluent PWA demonstrated higher vulnerability to domain-general cognitive control deficits compared to fluent PWA. Performance on verbal and non-verbal cognitive control tasks significantly overlapped in the non-fluent group only. Both groups recruited non-verbal cognitive control during language comprehension and verbal cognitive control during picture naming. Only non-fluent PWA relied on domain-general relational reasoning during language comprehension. These findings reinforce the importance of cognitive assessment in aphasia.

KEYWORDS:

• Aphasia
• cognitive control
• aphasia types
• auditory comprehension
• picture naming

Acknowledgements

Our sincere gratitude goes to Dr. Anatoly Skvortsov for his kind help in providing access to the participants with aphasia. We thank the editor and two anonymous reviewers for their insightful comments and suggestions.

Disclosure statement

No potential conflict of interest was reported by the authors.