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Sensorimotor reactivity in passive and active discrimination of ASL: A preliminary analysis of EEG mu rhythm evidence.
Edith Dong1; 1Gallaudet University
Speech perception has been routinely investigated through analysis of the mu rhythm as recorded by electro/magneto-encephalography. The mu rhythm has repeatedly been shown to be sensitive to the sensorimotor and cognitive demands associated with speech perception tasks from simple (passive perception) to more complex (discrimination and discrimination in noise). Primarily, these studies have utilized auditory and/or visual speech signals while varying task difficulty to assess mu rhythm reactivity over the time course of the stimulus to differentiate between automatic sensory-to-motor transformations and general cognitive demands. Evidence exists supporting both these interpretations, with a strong focus on spoken language, auditory-to-motor transformations, and general cognitive demands such as working memory and attention. Limited evidence exists investigating similar processes in visual/manual languages such as American Sign Language (ASL). ASL utilizes single or two handed signs that are characterized by hand-shape, movement, and position, with additional modification and meaning cues carried by facial expression. The goal of this preliminary study was to investigate mu rhythm reactivity in ASL perception and discrimination tasks, differentiating activation between automatic visuo-motor transformations and cognitive demands. Participants watched a control condition (modulated/kaleidoscope signs), and 3 test conditions (one handed left/one handed right/two handed). Each test condition included 80 trials and was run twice, once passively, once with a required response (same/different). EEG data were collected with a 32 channel Emotiv Flex system and analyzed with MATLAB and EEGLab. Mu rhythm results on pilot data suggest that mu-alpha and beta suppression is present in passive and active discrimination tasks, though stronger in discrimination tasks. In addition, one and two handed signs revealed different patterns of mu suppression across the left and right sensorimotor areas, suggesting visuo-motor mapping accurately reflects motor demands associated with self-reproduction of the signal. Though preliminary, this study suggests that perception of ASL similarly recruits and modulates the sensorimotor mu rhythm via changes to task demand while reflecting sensory-to-motor transformation across both the left and right hemispheres.