Speech-perception-in-noise deficits in dyslexia: a possible method to improve speech perception abilities
The exact cause of developmental dyslexia, a specific learning disorder characterized by severe reading and spelling difficulties, remains widely debated. Growing evidence exist that dyslexia is related to a temporal processing deficit. Hence, a low-level auditory dysfunction to process temporal information, might result in a subtle speech perception deficit and in turn interfere with the development of phonological representations and literacy skills. Previous results from our ongoing work indeed reveal low-level temporal deficits, mainly with processing specific onset cues. Moreover, these transient parts of the speech signal, such as onsets, are most important for speech intelligibility in normal-hearing listeners. Therefore we hypothesize that enhancing these particular cues in the speech signal might benefit speech processing in adults with dyslexia. An Envelope Enhancement strategy (EE, Koning and Wouters, 2012) was implemented to amplify the onsets of the speech envelope without affecting other parts of the speech signal.
In the present study we investigated (1) speech-in-noise abilities in a group of dyslexic and normal reading adults and (2) the potential of the EE strategy in dyslexia research. We tested speech understanding in four different conditions: natural speech, vocoded speech and their enhanced versions. A constant procedure was followed using four fixed signal-to-noise ratios for each condition. Additionally, cognitive test of phonological awareness, language skills, verbal short term memory and working memory were administered to investigate possible confounding effects. The results of this study will be discussed at the conference.