Poster E62, Monday, March 27, 2:30 – 4:30 pm, Pacific Concourse
EEG Evidence for Differences in Audiovisual Speech Processing in Apraxia of Speech
Melissa Randazzo1, Karen Froud2; 1Adelphi University, 2Teachers College, Columbia University
Speech perception is a unique audiovisual experience because timing of the speech signal is influenced by overlapping gestures in coarticulation. Apraxia of speech (AOS) is a motor planning disorder that impairs coarticulation. Although AOS is a motor planning disorder, individuals with AOS may have a disruption to the perceptual system for speech gestures. To evaluate this hypothesis we compared audiovisual mismatch negativity (MMN) via the McGurk effect in adults with AOS and a comparison group. Participants viewed a speaker articulating the syllable /ba/ (standard) and /ga/ (deviant) while the auditory stimulus /ba/ remained consistent. Responses to this McGurk audiovisual condition were compared to an inverse McGurk audiovisual condition in which the visual stimulus remained constant while the auditory stimulus changed, and a visual-only condition to control for activity from changes to the visual stimulus. McGurk deviants elicited an MMN in the comparison group, while the AOS group exhibited a later, attention-based response, P300. The AOS group similarly responded to inverse McGurk deviants with a P300 response. In the visual-only control condition, the AOS group showed an MMN, suggesting influence of visual processing for conflicting multisensory information. The comparison group’s responses indicate early, automatic audiovisual integration of incongruent McGurk percepts while the responses of the AOS group show contributions of both attentional and visual processing. Response timing in the AOS group was correlated with aspects of motor speech production performance. Results support the hypothesis that AOS is a disorder beyond motor planning, including linguistic and cognitive systems.
Topic Area: LANGUAGE: Development & aging