Impaired lexical selection and fluency in post-stroke aphasia

Background: Deficits in fluent language production are a hallmark of aphasia and may arise from impairments at different levels in the language system. It has been proposed that difficulty resolving lexical competition contributes to fluency deficits.

Aims: The present study tested this hypothesis in a novel way: by examining whether narrative speech production fluency is associated with difficulty resolving lexical competition in spoken word recognition as measured by sensitivity to phonological neighborhood density.

Methods & Procedures: Nineteen participants with aphasia and 15 neurologically intact older adults identified spoken words that varied in phonological neighborhood density and were presented in moderate noise.

Outcomes & Results: Neurologically intact participants exhibited the standard inhibitory effect of phonological neighborhood density on response times: slower recognition of spoken words from denser neighborhoods. Among participants with aphasia, the inhibitory effect of phonological neighborhood density (less accurate recognition of spoken words from denser neighborhoods) was smaller for participants with greater fluency. The neighborhood effect was larger for participants with greater receptive vocabulary knowledge, indicating that the fluency effect was not a result of general lexical deficits.

Conclusions: These results are consistent with the hypothesis that impaired lexical selection is a contributing factor in fluency deficits in poststroke aphasia.