Assessing the neural dynamics of reading in deaf adults

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Poor reading skills represent a significant public health concern because low literacy is associated with many negative social and economic outcomes (e.g., poor employment opportunities, limited access to health care information, reduced civic engagement). A Priority Area in NIDCD’s strategic plan for 2017-2021 includes research to “Identify central and peripheral factors associated with the successful comprehension and use of written language for people who use sign language as their primary way of communication (pg. 48)”. To that end, this project investigates the neuro-cognitive processes that support successful reading in adult signers who were born deaf or became deaf in early infancy. The primary goal is to use psycholinguistic paradigms and event-related potentials (ERPs) to differentiate deafness-related from reading-related factors that impact the functioning of the reading circuit when deaf adults recognize single-words (Aims 1 and 2), identify multiple words in parallel (Aim 3), and comprehend sentences (Aim 4). Aim 1 tests the hypothesis that sensory-dependent neural plasticity impacts the time course of early visual and orthographic processes, but that later lexico-semantic processes are similar for deaf and hearing readers with comparable reading levels. Aim 2 tests the hypothesis that deaf readers prioritize the morpho-semantic route for reading morphologically complex words but that better spellers utilize the morpho-segmentation route. Aim 3 tests the hypothesis that deaf readers exhibit greater parafoveal-on-foveal word processing effects due to changes in the distribution of spatial attention associated with early deafness. Aim 4 tests this hypothesis for sentence-level processing and also investigates whether the previously identified difference in the ERP response to grammatical violations (the P600) for deaf readers is due to the type of violation and/or to effects of early language deprivation. These aims will be achieved through innovative methods that combine ERPs with novel flanker paradigms and with co-registered eye-movements during natural reading. We also use linear mixed effects regression to identify the effects of continuous measures of reading, spelling, and phonological skills on ERP components using single trial EEG data. The results of this project will advance our understanding of the neuroplasticity of the reading system and will be key to creating targeted remediation programs for deaf adults with poor reading ability. By understanding how skilled adult deaf readers compensate for reduced access to speech, interventions can be crafted to promote those skills. Overall, this project will help build a framework for creating new strategies to improve reading skills in deaf children and adults.