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The interplay between orthography and phonology in word reading: an MEG study of deaf skilled readers
Poster Session D, Saturday, September 13, 5:00 - 6:30 pm, Field House
This poster is part of the Sandbox Series.
Chiara Luna Rivolta1, Sendy Caffarra2,3, Brendan Costello1,4, Manuel Carreiras1,4,5; 1Basque Center on Cognition, Brain and Language (BCBL), 2University of Modena and Reggio Emilia (Unimore), 3Stanford University, 4Ikerbasque, Basque Foundation for Science, 5University of the Basque Country (UPV/EHU)
Deaf individuals often face challenges in achieving high levels of reading proficiency due to limited access to auditory phonological information. This study focuses on a subgroup of highly skilled deaf readers to investigate the neural substrates of phonological and orthographic processing during successful reading in the context of deafness. Twenty-five prelingually deaf skilled readers of Spanish and 25 hearing controls matched on reading level participate in a magnetoencephalography (MEG) experiment: they silently read single words presented on a screen while performing a low-level perceptual task (asterisk-detection). The stimuli are phonologically or orthographically manipulated to fall into one of the following conditions: real words, consonant strings, pseudowords and either pseudohomophones, which sound the same as a real Spanish word (e.g. abril→avril), or transposed-letter pseudowords (e.g. generoso→gerenoso) depending on the type of manipulation. There are 100 stimuli for each condition and 80 asterisk trials. Analysis and final results will be presented at the SNL conference. We will compute the magnetic counterparts of N400 and N250 ERPs associated with each stimuli condition and compare relevant conditions within and across participant groups. We predict that deaf readers will show similar N400 effects for pseudohomophones and pseudowords, whereas hearing readers will show an attenuated N400 effect for pseudohomophones. This pseudohomophone effect (the difference between pseudohomophone and pseudoword conditions) in hearing readers reveals the role of phonological representations during word reading; the absence of this effect would suggest that deaf readers do not activate phonology, and that speech-based phonology is not necessary for proficient reading in this population. We expect orthographic processing to elicit earlier activity, reflected in the N250 ERP component. Previous work shows conflicting evidence regarding orthographic coding in deaf population. Hearing readers have flexible representations of letter position, as shown by the facilitatory effect of transposed-letter priming. In contrast, if deaf readers have more rigid orthographic representations, we expect stronger N250 effects for the transposed-letter condition compared to hearing-matched participants. We will also exploit MEG's spatial resolution to localize these effects at source level. Single-word reading activates, in both deaf and hearing readers, a left lateralized network that includes the inferior frontal gyrus, the superior temporal sulcus, and the inferior temporal gyrus. Previous research has shown that abstract orthographic representations in both groups of readers activates the left visual word form area (VWFA). We expect deaf readers to also show recruitment of the corresponding region in the right hemisphere. The temporal resolution of MEG and the sensitivity of ERPs to distinct orthographic and phonological mechanisms will allow us to detect subtle aspects of online linguistic processing that behavioral studies alone cannot reveal. If deaf readers show more rigid orthographic coding, this could reflect heightened orthographic sensitivity as a compensatory strategy for reduced access to auditory phonology. Our findings will add to the debate on the relative contributions of phonology and orthography to reading in the context of deafness and will help uncover alternative neural mechanisms leading to high levels of reading performance in this population.
Topic Areas: Reading, Signed Language and Gesture