Neural Correlates of American Sign Language Phonological Processing in Deaf Native Signers: An fMRI Study of Handshape, Location, and Movement Parameter Extraction

This study investigates fMRI neural correlates of ASL phonological parameter processing (handshape, location, movement) in deaf native signers compared to hearing ASL learners and hearing non-signers within the context of linguistics and cognitive neuroscience, an area of growing scientific importance given its implications for ASL language teaching neuroimaging-informed methods, cochlear implant candidacy assessment, and signed-spoken language processing comparative neurolinguistics. Using event-related fMRI (TR=2s, 3T Siemens Prisma) with ASL minimal-pair videos differing in single phonological parameter, GLM contrast analysis, and ROI analysis of left perisylvian, right parietal, and visual cortex regions, we examine ASL phonological features processed in left hemisphere language network (IFG, STG, SMG) analogous to spoken language phonology, with additional right parietal and dorsal visual stream engagement for spatial-motoric sign parameter analysis absent in spoken language in 72 participants: 24 deaf native signers (mean age onset of signing: birth), 24 hearing late learners (mean 8.4 years ASL experience), 24 hearing non-signers; all right-handed drawn from MRI facility at Great Lakes University Hospital, 3T Siemens Prisma, 64-channel head coil, 1.2 mm isotropic MPRAGE anatomical and 2 mm EPI functional sequence. Results indicate that deaf native signers show significant left IFG (Broca) activation for handshape discrimination (t=6.84, p<0.001) and bilateral SPL for location discrimination; hearing late learners show weaker but similar pattern; non-signers show only right occipital and motion area activation (p < 0.001), with deaf signers: IFG t=6.84; SPL bilateral for location; late learners show 58% of native signer effect size as the primary quantitative benchmark. Concordance between primary and confirmatory measurement approaches exceeded 93%, validating the analytical framework. These findings contribute empirically to linguistics and cognitive neuroscience and carry actionable implications for the design of programs and policies targeting ASL language teaching neuroimaging-informed methods, cochlear implant candidacy assessment, and signed-spoken language processing comparative neurolinguistics.