The impact of phonological or semantic impairment on delayed auditory repetition: Evidence from stroke aphasia and semantic dementia

Abstract

Background/Aims: This study aimed to evaluate the interactive account of repetition by examining the influence of factors that differentially tapped semantic and phonological processing in a case series of patients with semantic or phonological impairment. Methods & Procedures: We compared two patient groups: predominantly phonologically impaired cases with aphasia following cerebrovascular accident, and patients with semantic dementia. Immediate repetition was contrasted with repetition after a 5-second filled delay, and lexicality, frequency, and imageability were manipulated—therefore both the task and the neuropsychological impairment biased processing in favour of either lexical-semantic or phonological capacities. Outcomes & Results: Substantial interactivity was observed between phonological/semantic impairment and variables largely tapping these processes. The phonologically impaired patients showed substantial effects of lexicality and imageability that were larger in delayed than immediate repetition. The semantically impaired patients exhibited the complementary pattern, showing reduced effects of these lexical-semantic variables and a delay effect that was larger for more poorly comprehended, low-frequency items. Semantic errors were related to phonological deficits whereas semantic impairment led to an increase in phonological errors. The phonologically impaired stroke cases also made more perseverative responses. Conclusions: These findings support the view that repetition is underpinned by interaction between semantics and phonology within a single route and not by distinct lexical and sub-lexical pathways. The results also provide evidence of a continuum between phonological and deep dysphasia.