Search Abstracts | Symposia | Slide Sessions | Poster Sessions
Dissociating phonological tuning from reading skill: Evidence from the temporoparietal cortex in deaf and hearing adults
Poster Session B, Wednesday, September 30, 4:30 - 6:30 pm, Wangari Maathai
Laurie S. Glezer1, Stephen McCullough1, Brennan Terhune-Cotter2, Karen Emmorey1; 1Lab for Language and Cognitive Neuroscience, San Diego State University, 2Institute of Cognitive Neuroscience, University College London
Phonological processing is widely thought to be central to successful reading development in hearing individuals, with the temporoparietal cortex (TPC) considered to be an essential region in the brain for encoding phonological information derived from print. In deaf individuals, however, phonological awareness accounts for only a small fraction of the variance in reading ability, with overall language ability being a larger predictor of reading success (Mayberry et al., 2011). In previous studies, we examined the phonological representations encoded in the TPC during reading using homophone pairs in an fMRI rapid adaptation paradigm in hearing skilled and less-skilled readers and in deaf skilled readers (Glezer et al., 2016, 2018, 2019). Skilled hearing readers showed whole-word tuning to phonology in the TPC while hearing people who have difficulty reading showed less precise phonological representations in this region. Interestingly, skilled deaf readers showed the same response profile as less-skilled hearing readers, suggesting that precise phonological representations in this area are not necessary for proficient reading to occur. These studies, however, used homophones — real words sharing phonological form but differing in orthography and meaning (e.g., pane, pain) — leaving open the possibility that semantic differences between homophone pairs contributed to the observed adaptation patterns. Disentangling phonological tuning from semantic processing requires stimuli that share phonological form without carrying lexical or semantic identity, i.e., pseudohomophones such as bloo (blue) or brane (brain). In the current study, we used fMRI to compare skilled deaf and hearing adult readers as they viewed real words (RWs), pseudowords (PWs), and pseudohomophones (PHs). Because orthographically PHs carry no lexical or semantic identity, we can isolate the phonological representations accessed through print providing a more direct probe than what has been used in prior work. We examined BOLD signal differences within individually localized TPC ROIs for RWs, PHs, and PWs. Because PHs and RWs both map to phonologically real words, they should elicit equivalent responses if the reader is engaging the full phonological lexical code, and both should produce greater responses than PWs, which do not have lexical phonological representations. However, if phonological representations accessed through print are coarser or are not automatically engaged, PHs would not activate a lexical phonological representation and would instead produce a response similar to PWs. Our results show that deaf and hearing skilled readers present with distinct response patterns. Hearing readers showed equivalent responses to PHs and RWs, with both greater than to PWs ((RW=PH)>PW), suggesting the lexical-level phonological representations were accessed from print. Deaf readers, on the other hand, showed the largest response to RWs and equivalent responses to PHs and PWs (RW>(PH=PW)), indicating that the whole-word phonological form was not reliably accessed from print. These findings indicate that in skilled deaf readers, the TPC is engaged, but encodes phonological information from print with reduced precision and/or automaticity. This pattern supports the proposal that skilled deaf readers can achieve high-level literacy through a unique reading architecture in which the direct orthographic-to-semantic pathway carries the primary functional load for mapping print onto meaning.
Topic Areas: Reading, Phonology