Akshi .¹, Elizabeth Saccone¹, Miriam Hauptman¹, Matthew Sampson¹, Marina Bedny¹; ¹Johns Hopkins University

The role of Fusiform Face Area (FFA) in supporting linguistic processing remains an open question. Signed languages such as American Sign Language (ASL) use faces and body-parts (hands, body orientation etc.) as articulators, with facial expressions being an integral part of ASL grammar. We investigate functional profile of FFA in Deaf signers and hearing non-signers using individual subject functional localization. Congenitally and profoundly Deaf adults (n=8) completed an ASL localizer (conditions: signed ASL sentences, meaning and perceptually matched Action videos, and a blurred low-level Control condition). The same participants also completed a dynamic face localizer (conditions: faces, objects, scenes, body parts, scrambled objects) and a written English localizer (conditions: sentences, nonword sequences; n=7). A hearing non-signer group (n=14) completed the same face localizer as the Deaf group and an analogous spoken English localizer with English and foreign language sentences. We tested whether the lateral fusiform, i.e., the typical location of the fusiform face area (FFA), develops specialization for perceptual processing of faces and bodies in sign language. In the Deaf group, face-preferring vertices inside an FFA anatomical mask (from a separate group of hearing participants) responded comparably to ASL and Action conditions (significantly more than low-level control). However, ASL-selective vertices in the same FFA mask (ASL > Action; leave-one-run-out) showed robust preference for ASL over Action and low-level Control, and also responded significantly more to face and body condition compared to other categories. In contrast, written English-selective vertices (sentences > nonwords) in Deaf participants did not show such preference for faces and bodies. Similarly, spoken English-selective vertices in FFA in hearing non-signers did not exhibit face/body preference. The results suggest that experience with a visuo-manual language, such as ASL, in Deaf signers leads to specialization of a subset of FFA vertices for sign-language-specific effectors (faces, body parts).