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Neural substrates of orthographic coding in skilled deaf readers.
Poster Session E, Sunday, September 14, 11:00 am - 12:30 pm, Field House
This poster is part of the Sandbox Series.
Ruiqing zhang1,2, Chiara Luna Rivolta1, Brendan Costello1,3, Manuel Carreiras1,2,3; 1Basque Center on Cognition, Brain and Language (BCBL), Spain, 2University of the Basque Country (UPV-EHU), Spain, 3Ikerbasque, Basque Foundation for Science, Spain
Deaf individuals lack access to auditory phonology and may rely more on visual-orthographic processing to develop proficient reading ability. However, the details of orthographic coding, specifically how they represent letter position versus identity, remain unresolved. Furthermore, it is unclear whether enhanced visual processing in deaf readers is domain-specific (limited to language) or extends to other symbolic systems like digits. This study addresses three questions: (1) Can auditory deprivation be compensated by hyper-precise orthographic coding? (2) Does this precision mechanism prioritize position-based or identity-based letter encoding? (3) Is enhanced visual processing common to both linguistic and non-linguistic domains? By comparing skilled deaf and hearing readers, we investigate whether deaf individuals recruit similar or different neural mechanisms for orthographic processing. Participants (25 prelingually deaf and 25 hearing adults matched for reading ability) completed a fMRI same-different perceptual task (adapted from Carreiras et al., 2015). Participants judged whether two sequentially presented four-character strings (containing either letters or digits) were identical or different. By manipulating the internal characters of the four-character strings we created three experimental conditions: Identical (e.g., KGBT→KGBT), Transposed (e.g., KGBT→KBGT) or Replaced (e.g., KGBT→KPRT). We will use linear mixed-effects models to investigate the transposition cost, operationalized as the difference in reaction time (RT) and accuracy between Transposed and Replaced conditions, across groups and character types (letters/digits). Similarly, we will analyze the fMRI data to inspect neural differences in the transposition cost effects between groups and character types. ROI-level functional connectivity analysis will be conducted to examine network-level differences. Behaviorally, hearing readers should show greater transposition costs (slower RTs, lower accuracy) for letters than for digits, in line with Carreiras et al. (2015). Based on preliminary data, deaf readers seem to display a similar pattern as hearing readers suggesting that any between-group difference in transposition cost effects is small or non-significant. However, if deaf readers employ a more rigid orthographic coding strategy, particularly with regard to position, they may exhibit faster RT and/or higher accuracy in Transposition condition than hearing readers. At the neural level, we anticipate that deaf readers will show greater involvement of the right hemisphere during general character processing compared to hearing readers, likely driven by the reorganization of the language network due to sign language knowledge. If deaf readers exhibit hyper-precise orthographic coding we expect to see distinct activation associated with letter and digit processing within the ventral occipitotemporal cortex (vOTC) for deaf compared to hearing readers. Additionally, if deafness induces neural reorganization due to greater reliance on visual information, we predict a unique profile in the vOTC, along with altered connectivity with other regions, such as the superior parietal cortex, which plays a role in letter position coding. Preliminary results will be presented at the SNL conference. This study offers insights into reading development in sensory-deprived populations and how neuroplasticity accommodates diversity of linguistic experience.
Topic Areas: Reading,