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Poster B69, Wednesday, November 8, 3:00 – 4:15 pm, Harborview and Loch Raven Ballrooms

Ventral occipito-temporal responses to written texts and fingerspelling in congenitally deaf adults

Tae Twomey1, Dafydd Waters1, Cathy Price1, Mairéad MacSweeney1;1University College London

Previous studies have shown greater activation for fingerspelling relative to sign language stimuli in the left ventral occipito-temporal (vOT) cortex – an area considered to be important in reading. This effect has been shown for the perception (semantic judgement, Waters et al., 2007; Emmorey et al., 2015) and the production (translation from English text, Emmorey et al., 2016) of fingerspelling. Although this effect has been attributed to orthographic processing, fingerspelling has never been directly compared to written text, partly due to the inherent difference in movement between the two orthographic forms. Demonstrating that fingerspelling is processed in vOT in the same way as text would provide further support to the possible role of fingerspelling in reading acquisition. Here we controlled for movement by presenting texts sequentially and investigated the vOT responses to fingerspelling and text in congenitally deaf adults, using functional magnetic resonance imaging (fMRI). Deaf native signers of British Sign Language, who scored more than 80% (Mean= 91%) on a fingerspelling test, were invited to participate. We manipulated input form (fingerspelling/sequentially presented text), lexicality (words/letterstrings) and task (linguistic/perceptual), resulting in a 2 x 2 x 2 factorial design. In the linguistic task, participants decided whether the item was a word or not. In the perceptual task, participants decided if any portion of the model’s right hand touched the palm of her left hand (fingerspelling) or if the stimulus contained a letter with an ascender (sequential text). Both accuracy and reaction times showed significant main effects of task, input form and lexicality. The accuracy data also showed a significant interaction of task and lexicality. Post-hoc tests confirmed that participants were more accurate on letterstrings than words during the linguistic task while accuracy did not differ between words than letterstrings during the perceptual task. The reaction time data showed a significant interaction of input form and lexicality. Post-hoc tests confirmed that participants took significantly shorter time to respond to letterstrings than words when the stimuli were presented as sequential text but there was no difference for fingerspelling. Given the effects of all the experimental factors, RTs were included as a covariate in the fMRI analyses. Greater activation for fingerspelling relative to sequential text was found in the occipital regions bilaterally, the left posterior middle temporal gyrus and the right precentral gyrus. There were no regions where activation was greater for sequential text than fingerspelling. The perceptual task elicited stronger activation than the linguistic task in bilateral middle occipital gyrus and the right angular gyrus. The opposite contrast showed no significant activation. Within a pre-defined, a priori anatomical region-of-interest mask in vOT, there was a significant main effect of lexicality (words>letterstrings). There were no significant effects of task, input form or interactions in vOT. The presence of a main effect of lexicality without interactions in vOT suggests that this region responds similarly to fingerspelling and sequential text despite very different perceptual properties. The finding supports the argument that fingerspelling may be a useful tool to support reading acquisition in deaf people.

Topic Area: Writing and Spelling

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