Effects of verb meaning on lexical integration in agrammatic aphasia: Evidence from eyetracking

• Two eyetracking experiments tested lexical integration in agrammatic aphasia.
• Healthy listeners used verb meaning to predict and integrate subsequent arguments.
• Aphasic listeners showed intact use of verb meaning to integrate overt arguments.
• Prediction of upcoming arguments was impaired in aphasic listeners.
• Deficits in prediction may result from damage to the left inferior frontal cortex.

Relatively little is known about the time course of access to the lexical representations of verbs in agrammatic aphasia and its effects on the prediction and integration of the verb's arguments. The present study used visual-world eyetracking to test whether verb meaning can be used by agrammatic aphasic individuals to predict and facilitate the integration of a subsequent noun argument. Nine adults with agrammatic aphasia and ten age-matched controls participated in the study. In Experiment 1, participants viewed arrays of four objects (e.g., jar, plate, stick, pencil) while listening to sentences containing either a restrictive verb that was semantically compatible only with the target object or an unrestrictive verb compatible with all four objects (e.g., Susan will open/break the jar). For both participant groups, the restrictive condition elicited more fixations to the target object immediately after the verb. Experiment 2 differed from Experiment 1 in that the auditory sentences presented were incomplete (e.g., Susan will open/break the…). For controls, restrictive verbs elicited more target fixations immediately after the verb; however, the effects of verb type were noted downstream from the verb for the aphasic listeners. The results suggest that individuals with agrammatic aphasia have preserved ability to use verb information to facilitate integration of overt arguments, but prediction of upcoming arguments is impaired. Impaired lexical-semantic prediction processes may be caused by damage to the left inferior frontal gyrus, which has been argued to support higher-level lexical processes.