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Poster E68, Friday, November 10, 10:00 – 11:15 am, Harborview and Loch Raven Ballrooms

Neural signatures of sign language processing in bimodal bilinguals

Brendan Costello1, Pedro Paz-Alonso1, Manuel Carreiras1,2,3;1BCBL, Donostia-San Sebastian, Spain, 2Ikerbasque, Basque Foundation for Science, Bilbao, Spain, 3University of the Basque Country, Spain

Sign language (SL) provides the opportunity to examine modality effects in language processing. Previous neuroimaging evidence has shown that SL recruits a similar set of left-lateralized perisylvian regions to those engaged in spoken languages, including the inferior frontal gyrus (IFG). However, there are still many unanswered questions regarding the functional signatures of SL processing: Does regional engagement of left-lateralized perisylvian regions during language processing differ as a function of modality? Is there a specific functional signature of SL processing? To what extent does language processing rely on different neural dynamics as a function of being a native versus a L2 signer? The present fMRI study sought to investigate these questions in three different groups of hearing bilinguals: 23 native Spanish Sign Language (LSE)-Spanish bilinguals, 20 late LSE-Spanish bilinguals and 23 bilingual controls with no knowledge of LSE. In an event-related design, participants processed LSE signs, presented as (silent) videos, and Spanish words, presented either aurally (sound only) or audiovisually (a video of a model saying the word with sound). Each of these three types of stimuli was contrasted against corresponding baselines, consisting of scrambled video and/or rotated speech. A low-level visual perceptual task (indicating the orientation of an arrow that appeared on 10% of trials) was used to ensure that participants maintained attention on the stimuli; these trials were excluded from the analysis. Results confirmed that SL and spoken language recruited a similar set of left-perisylvian regions. Nevertheless, signers exhibited significant stronger regional engagement for SL processing than for spoken language processing across left-perisylvian nodes, including the IFG pars triangularis and opercularis, posterior temporal gyrus and parietal cortex. Importantly, compared to sign-naïve controls, signers exhibited reliable stronger activation in left IFG and posterior temporal gyrus extended to the supramarginal gyrus, as well as tighter functional coupling among these regions, during SL processing. Finally, L2 signers showed stronger recruitment of right superior parietal cortex (SPC) and stronger functional connectivity between right SPC-left posterior temporal gyrus for processing signs relative to native signers. These results constitute the strongest evidence so far showing differential regional and functional connectivity signatures of SL processing between signers and non-signers and between native and late signers hearing bilinguals.

Topic Area: Signed Language and Gesture

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