No abstract

It is known that deaf individuals usually outperform normal hearing subjects in speechreading; however, the underlying reasons remain unclear. In the present study, speechreading performance was assessed in normal hearing participants (NH), deaf participants who had been exposed to the Cued Speech (CS) system early and intensively, and deaf participants exposed to oral language without Cued Speech (NCS). Results show a gradation in performance with highest performance in CS, then in NCS, and finally NH participants. Moreover, error analysis suggests that speechreading processing is more accurate in the CS group than in the other groups. Given that early and intensive CS has been shown to promote development of accurate phonological processing, we propose that the higher speechreading results in Cued Speech users are linked to a better capacity in phonological decoding of visual articulators.

Cued Speech (CS) is a manual communication system that makes use of visual information from speechreading combined with handshapes positioned in different places around the face in order to deliver completely unambiguous information about the syllables and the phonemes of spoken language. This chapter reviews research showing that CS (i) enhances speech perception, (ii) facilitates language development in the phonological, lexical, and morpho-syntactical domains, and (iii) allows the development of robust and precise phonological representations, which are recruited in cognitive abilities such as rhyming, remembering, reading, and spelling. Findings from research reviewed also shows that early exposure to CS, before learning to read, facilitates the acquisition of the alphabetic principle. We also discuss two new research lines about CS: (1) How is CS processed by the brain and the similarities and differences with the processing of audio-only and audio-visual language and (2) Is CS compatible with a cochlear implant? We support our view that exposure to CS before or after implantation could be important in the aural rehabilitation process of cochlear implantees.

We present here the first neuroimaging data for perception of Cued Speech (CS) by deaf adults who are native users of CS. CS is a visual mode of communicating a spoken language through a set of manual cues which accompany lipreading and disambiguate it. With CS, sublexical units of the oral language are conveyed clearly and completely through the visual modality without requiring hearing. The comparison of neural processing of CS in deaf individuals with processing of audiovisual (AV) speech in normally hearing individuals represents a unique opportunity to explore the similarities and differences in neural processing of an oral language delivered in a visuo-manual vs. an AV modality. The study included deaf adult participants who were early CS users and native hearing users of French who process speech audiovisually. Words were presented in an event-related fMRI design. Three conditions were presented to each group of participants. The deaf participants saw CS words (manual + lipread), words presented as manual cues alone, and words presented to be lipread without manual cues. The hearing group saw AV spoken words, audio-alone and lipread-alone. Three findings are highlighted. First, the middle and superior temporal gyrus (excluding Heschl’s gyrus) and left inferior frontal gyrus pars triangularis constituted a common, amodal neural basis for AV and CS perception. Second, integration was inferred in posterior parts of superior temporal sulcus for audio and lipread information in AV speech, but in the occipito-temporal junction, including MT/V5, for the manual cues and lipreading in CS. Third, the perception of manual cues showed a much greater overlap with the regions activated by CS (manual + lipreading) than lipreading alone did. This supports the notion that manual cues play a larger role than lipreading for CS processing. The present study contributes to a better understanding of the role of manual cues as support of visual speech perception in the framework of the multimodal nature of human communication.

During a visual rhyming task, deaf participants traditionally perform more poorly than hearing participants in making rhyme judgements for written words in which the rhyme and the spelling pattern are incongruent (e.g. hair/bear). It has been suggested that deaf participants' low accuracy results from their tendency to rely on orthographic similarity. To test this interpretation more directly, we compared profoundly and prelingually deaf, orally educated participants and hearing participants' accuracy during a visual rhyming judgement task in which the two words of a pair share the orthographic rime, in order to discourage usage of a purely orthographic strategy. Accuracy was lower in deaf than in hearing participants. The gradient of difficulty between items, together with the finding of a significant correlation between accuracy and the consistency of the grapheme to rhyme, suggest that difference in accuracy between groups might be explained by an over regularization in deaf people, which is probably linked to less diversified phonological representations.