[PS-1.3] Investigating brain lateralization during speechreading and reading in deaf adults using functional transcranial Doppler sonography (fTCD)

Gutierrez-Sigut, E. 1, 2 , Mousley, V. 2 , Monroy, L. 2 , Harte, S. 2 & MacSweeney, M. 2

1 University of Valencia
2 University College London

Phonological processing is strongly linked to reading ability in hearing people. It has been proposed that as reading development progresses, visual word recognition becomes increasingly left lateralized due to mapping of orthographic forms onto the already left lateralized phonological forms (Maurer and McCandliss, 2008). In this line, greater phonological awareness has been linked with stronger left lateralization for visual word processing (Sacchi & Laszlo, 2016). This process might be challenging for deaf readers, whose phonological representations, constructed upon speechreading (lipreading) and articulatory feedback, might be underspecified.

Here we investigate lateralization in profoundly deaf adults during language tasks using functional Transcranial Doppler sonography (fTCD). We measured laterality indices (LIs) during language generation (semantic fluency), rhyme judgement tasks, reading and speechreading of short stories.

Results for language generation (the gold standard task to establish hemispheric lateralization) showed that participants were predominantly left lateralized. The strength of lateralization for the rhyme judgment task was lower but not significantly different from the generation task. Significantly lower LIs were found for both the reading and speechreading tasks than for the generation task. We discuss the gradation of lateralization for this battery of tasks in terms of their language demands (see Bradshaw et al., 2017).