Purpose: Healthy speakers use both word-level and structure-level information to ease sentence production processes. Structural priming facilitates message-structure mapping in aphasia. However, it remains unclear if and how word-level information affects off-line and on-line sentence production in persons with aphasia (PWA). This eyetracking-while-speaking study examined the effect of lexical priming on production of syntactic (active/passive) structures in PWA.
Method: Eleven PWA and twenty healthy older adults (HOA) described transitive actions (woman pulling horse) following lexical priming, wherein the relative ease of lexical retrieval for the Agent or Theme was manipulated via an auditory probe (what is happening with the woman/horse ?). It was examined whether or not PWA produce the sentence structure that allows earlier production of the primed word (e.g., passives when Theme was primed). Participants' eye fixation times to each character (Agent, Theme) were also monitored to examine if PWA show priming-induced preferential looks to one character from the earliest stage of production, consistent with word-driven planning.
Results: HOA showed increased production of passives over actives in the Theme vs. Agent prime condition. In eye fixation data, HOA showed priming-induced Theme advantage from the earliest time window (picture onset-400 milliseconds). PWA also showed a significant priming effect in off-line sentence production, with this priming effect being greater for the individuals whose syntactic processing is better preserved. In eye fixation data, however, PWA showed preferential fixations to the primed character at a later stage of sentence planning (400-800 milliseconds), following equal fixation time to Agent and Theme during the earliest time window.
Conclusion: HOA showed word-driven production in both off-line and real-time (eye fixations) production. Lexical accessibility effectively drove off-line syntactic production in PWA, especially for those whose syntactic capacity remains relatively preserved. However, PWA showed advanced processing of both characters in earliest eye fixation data, suggesting that successful word-driven off-line syntactic production was associated with atypical real-time sentence planning in aphasia.
Keywords: aphasia; eyetracking; grammatical encoding; incrementality; lexical priming; sentence production.