Parameters of semantic and phonologic activation in speakers with aphasia with and without apraxia of speech

A cross-modal picture-word interference paradigm was employed to investigate parameters of semantic and phonologic activation in four speakers with aphasia (APH), four speakers with aphasia and a concomitant apraxia of speech (APH/AOS) and ten speakers with normal speech and language (NC). Participants named pictured objects in the context of listening to words that were either semantically or phonologically related to the picture labels. Relative to the presentation of the target picture, these semantic and phonologic interfering stimuli (IS) were presented at seven different temporal asynchronies, labelled stimulus onset asynchronies (SOA). Speech onset latencies were analysed and SOAs at which the semantic and phonologic IS began and ceased to slow naming latencies were obtained. The time course of semantic and phonologic processing was inferred using the following four activation parameters: (1) interference onset SOA; (2) interference offset SOA; (3) peak interference SOA; and (4) activation period. The results indicated that onset of phonologic activation occurred later for APH/AOS than for APH participants. Additionally, the offset of semantic interference was significantly delayed in the APH/AOS group relative to the APH group. It is hypothesized that phonologic activation accrues more slowly in aphasic individuals who have a concomitant apraxia of speech and that prolonged semantic activation may be necessary to achieve sufficient levels of phonologic activation for naming.