Thursday, November 21, 2024
11/21/2024
Project Summary Sign language is vital to the lives and well-being of many deaf people in the United States who rely on this mode of communication. However, current theories in linguistics, psychology, and cognitive neuroscience have all been developed primarily from investigations of spoken language. The focus on speech leaves open many critical questions about linguistic phenomena that are fundamentally shaped by the visual-manual modality. NIDCD recognizes these gaps in our understanding – the Strategic Plan states, ”Enhancing our understanding of visual-manual language systems opens a window into general human cognition (pg. 32).” This project aims to develop a neurobiological model of sign language perception and comprehension that takes into account essential modality-specific phenomena: phonology without sound, lexical iconicity (non-arbitrary mappings between the form and meaning of signs), and `spatial syntax' (the use of locations in signing space to express grammatical roles and co-reference). Aim 1 of the project is to map the cortical representation of phonological structure in American Sign Language (ASL) using functional Magnetic Resonance Imaging (fMRI). fMRI adaptation methods will be used to investigate whether body-selective neural regions become tuned to linguistic handshapes and body locations in signers. In a second fMRI study, Phonological Neighborhood Density in ASL will be manipulated to identify neural areas that support lexical-level phonological representations. Aim 2 of the project is to identify the impact of iconicity on lexical representations and learning. Event-Related Potentials (ERPs) will be used to assess whether effects of iconicity are task dependent (e.g., related to the use of picture stimuli) or reflect distinct neural representations for iconic signs (e.g., more robust encoding of sensory-motor semantic features). ERPs will also be used to investigate whether brain responses to iconic signs change with learning and whether learners represent signs as wholistic gestures or are sensitive to internal phonological structure. Aim 3 of the project is to identify the neural network involved in comprehending `spatial syntax'. fMRI will be used to determine whether right parietal cortex is engaged when understanding ASL verbs that are directed toward locations in signing space (R-loci) to indicate grammatical roles. A second fMRI experiment is designed to identify the neural correlates of spatial indexing (the establishment and maintenance of R-loci). Overall, the project aims to enhance our understanding of the neurobiology of visual-manual language, which will provide a translational foundation for treating injury to the language system and for diagnosing language impairments in deaf individuals.
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