When confronted with a severe to profound congenital bilateral hearing loss, cochlear implantation is considered to be the preferential treatment method as it restaures auditory function and enables language acquisition for communication purposes. When cochlear implantation is done before 2 and a half years old, better results are obtained in terms of language, communication and social developement, as well as reading skills. However when a cochlear implantation occurs between 2 and 5 years of age, speech and language skills do develop but communication and reading skills are altered. Therefore, when a cochlear implant is placed before the age of 2 and a half we find ourselves within the maximal cerebral plasticity window for speech, language and communication developement.~This study is divided into two cohorts, the first aged 10-24 months and the second 3-7 years. All children will be seen for 5 sessions, spread out at regular intervals, over a period of 18 months and will participate in two perceptual tasks and two cognitive tasks. The children will also have a speech and language assessment at T-0 and T+12. The cochlear implanted patients will continue to be seen by the ENT service and the sessions will be organised to coincide with their natural follow up. As it is a non-interventional study, no follow-up would be needed. After the study patients will continue to receive the same quality of care.
The principal aim of this study is to evaluate the cortical developement of perceptual skills and executive functions over time, in children with cochlear implants aged 10-24 months and 3-7 years compared with normally hearing subjects (NHS). To do this, the investigator will use functional Near InfraRed Spectroscopy (fNIRS) during 4 tasks that engage the childs perceptual and cognitive skills over a period of 18 months. The performance scores obtained by each participants as well as the cortical activity will be analysed and decrypted.