The hierarchical organization of semantic knowledge in stroke aphasia: The role of feature sharedness and executive function

• We evaluate feature sharedness' impact on concept knowledge in stroke aphasia.
• We use a sentence verification task combining concept level × feature sharedness.
• Feature sharedness is the critical factor that accounts for task performance.
• The role of feature sharedness is exacerbated for stroke aphasia patients.
• Feature sharedness can explain superordinate deficits in stroke aphasia.

The present study directly evaluates the impact of feature sharedness on the differences between superordinate and basic-level concepts observed in aphasia patients due to fronto-temporal stroke. In particular, it was evaluated if feature sharedness composition explains the superordinate deficits observed in these patients. For this purpose we studied 6 stroke aphasia patients and 12 matched controls using a sentence verification task in which feature sharedness (more vs. less shared) and concept level (basic level vs. superordinate) were orthogonally manipulated. The results showed that sentences involving more shared features were processed faster and more accurately than sentences involving less shared features. This difference was particularly relevant in the processing of superordinate concepts, and was exacerbated for patients in relation to healthy controls. These findings suggest that deficits in executive function especially impact the processing of less shared features leading to superordinate deficits in stroke aphasia.