Poster E46, Thursday, August 22, 2019, 3:45 – 5:30 pm, Restaurant Hall
Sensorimotor EEG activity during sign production in deaf signers and hearing non-signers
Lorna Quandt1, Athena Willis1;1Gallaudet University
Background: Prior research suggests that the amount of experience an individual has with an action influences the degree to which the sensorimotor systems of their brain are involved in the subsequent perception of those actions. Less is known about how action experience and conceptual understanding impact sensorimotor involvement during imitation. We sought to explore this question by comparing a group of sign language users, who have a great deal of long term linguistic experience with signs, to a group of non-signers, for whom producing signs is novel and lacks conceptual meaning. We pitted the following two hypotheses against each other: 1) Deaf signers will show increased sensorimotor activity during sign imitation, and greater differentiation between sign types, due to greater prior experience and conceptual understanding of the signs; versus 2): Deaf signers will show less sensorimotor system activity and less differentiation of sign types in the sensorimotor system, because for those individuals sign imitation involves language systems of the brain more robustly than sensorimotor systems. Methods: We collected electroencephalograms (EEG) while fluent deaf American Sign Language (ASL) signers (N = 28) and hearing non-signers (N = 23) viewed videos of signs that had varied sensorimotor characteristics. Each of the two groups imitated videos that presented one-handed and two-handed ASL signs. Participants saw and then imitated 40 1-handed signs, and 40 2-handed signs which were matched on ASL frequency, iconicity, and flexion, and on frequency, # of phonemes, word length, and imageability for their English translations. Participants were given the task of imitating each presented sign after the demonstration was completed. Time-frequency data analysis was performed on alpha (8 - 13 Hz) and beta (14 - 25 Hz) oscillations during 2000 ms of sign production. We focused our analyses on electrodes in the central region of the electrode array, reflecting activity in the underlying primary somatosensory and motor cortices. Results: Both the deaf signing and hearing non-signing groups exhibited sustained central alpha/mu desynchronization during the production of signs, and a central beta desynchronization that was of shorter duration. Both groups also showed significantly different patterns of alpha/mu and beta desynchronization while producing 1-handed ASL signs compared to 2-handed ASL signs (p < .05, FDR corrected). The extent of alpha/mu desynchronization was significantly different between Deaf and Hearing groups, with the Deaf group showing more sustained alpha/mu desynchronization compared to the Hearing group (p < .05, FDR corrected), particularly ~1800 ms after the onset of sign production. Conclusion: We demonstrate that sensorimotor EEG rhythms in both Deaf and Hearing groups are sensitive to basic parameters of American Sign Language (number of hands used). The results suggest that knowledge of, and/or experience with American Sign Language leads to different patterns of sensorimotor activity during imitation of signs. The greater alpha/mu desynchronization during sign production in the Deaf group supports the notion that fluent knowledge of sign language results in greater recruitment of sensorimotor systems during production.
Themes: Signed Language and Gesture, Multisensory or Sensorimotor Integration
Method: Electrophysiology (MEG/EEG/ECOG)