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N400 and Sensorimotor EEG Responses to Iconicity in American Sign Language
Poster Session E, Friday, October 2, 11:00 am - 1:00 pm, Wangari Maathai
Meghan E. McGarry1, Lorna C. Quandt1; 1Gallaudet University
Signed and spoken languages differ significantly in their modality. The use of the visual-motor modality in signed languages allows for structured (iconic) mappings between a sign and its referent. These mappings allow for real-world features of the referent to be encoded in the form of the sign, such as the American Sign Language (ASL) sign SHARK, in which a hand takes on the place and appearance of a fin. Prior research has found a facilitatory effect of iconicity during both child and adult sign acquisition. This facilitation may be a product of embodied cognition. Research into embodied cognition has shown that during both child and adult language processing, prior knowledge from sensory-motoric experiences is accessed. Motorically iconic signs have iconic mappings that depict the signer handling or using the referent (for example, the ASL sign HAMMER shows the signer grasping and swinging a hammer). Because motorically iconic signs encode aspects of how the referent is used, this mapping may facilitate signers' access to their embodied cognition. In an American Sign Language (ASL) picture-naming task, a group of fluent deaf signers (n = 24) named pictures showing objects with either motorically iconic or non-iconic signs. We found that participants produced the motorically iconic signs significantly faster than the non-iconic signs (p = 0.032). We analyzed Event-Related Potentials (ERPs) and Time-Frequency Analyses (TFAs) from the picture-naming task. In the ERP analyses, we looked at the amplitude of the N400 component, an ERP component that indexes lexical activation and semantic processing and occurs roughly 400-600ms after stimulus presentation. Larger (more negative) N400 amplitudes indicate that participants are accessing more semantic information, including sensory-motoric elements of the referent. We found larger N400 amplitudes for motorically iconic signs compared to non-iconic signs. In the TFA analyses, we sought evidence of mu-rhythm desynchronization, which indexes sensorimotor engagement. Within the 400-600 ms time epoch and in the beta frequency band (14-25 Hz), we found greater desynchronization for motorically iconic signs than for non-iconic signs. This desynchronization suggests greater embodied engagement during lexical retrieval for motorically iconic signs. Taken together, the facilitated reaction times and EEG findings suggest that during lexical retrieval, fluent signers engage their embodied cognition to retrieve the desired sign, and that the recruitment allows them to more quickly retrieve signs for production. Next, we will conduct the same experiment with caregivers of Deaf/Hard-of-Hearing (DHH) children. These caregivers will have no knowledge of ASL but will learn the target signs during a structured training. We will investigate whether the same facilitatory effect is found for motorically iconic signs, suggesting that caregivers can leverage embodied cognition to support their learning. If so, motorically iconic signs may be a good starting point for new signers. Sign acquisition is the best protection against linguistic deprivation for DHH children, so any intervention that supports caregiver learning allows them to better communicate with their child and protects them from the lifelong effects of linguistic deprivation.
Topic Areas: Signed Language and Gesture,