Luc Arnal1, Diane Lazard 1,2
Institut de l’Audition, Institut Pasteur, Paris, France
2ENT surgery department, Institut Arthur Vernes, Paris, France

Mature brains are able to adapt to acquired sensory dysfunction. In case of hearing loss and oral communication difficulties, postlingual deaf adults follow two main strategies. One relies on a left-lateralized physiological, but relatively slow analytical pathway maintained by efficient lipreading skills. The second strategy consists in engaging the right hemisphere in an accelerated, non speech-dedicated network. This reorganization is efficient and rapid thanks to direct interaction with Broca’s area bypassing regular phonological steps. It relies on accelerated reading abilities. The first strategy will be beneficial in case of hearing rehabilitation (cochlear implantation), while the second option relevant during the deprived period will turn maladaptive. This active plasticity was evidenced in adults aged less than 65 years. When cochlear implantees are more than 65 years, they significantly perform less 2 years after surgery than a control sample aged 17-40 years. The reasons are still hypothetical. Among them, the relation between severe hearing loss in aging brains and dementia, and in particular Alzheimer’s disease, is questioned. Moreover, modification of sensitivity to salient events presented at 40 Hz (i.e. belonging to the roughness range) appears a promising potential biomarker of Alzheimer’s disease. Thus combining audiological and neurophysiological screening in the presymptomatic phase of Alzheimer’s disease may help preventing cognitive decline process by personalized interventions.

Acknowledgements: La Fondation pour l’Audition supports this work at Institut de l’Audition, Institut Pasteur.