In the case of sensorineural deafness occuring after language acquisition, it is now possible to restore an auditory environment by installing electrodes inside the cochlea. which directly stimulate the primary auditory afferents. Using a cochlear implant, some subjects recover the use of spoken language, whereas other subjects recover only the auditory alert function.. The large range of performances obtained with the same technology (new implant generation comprising around 20 electrodes) raises questions about the cerebral plasticity mechanisms that follow auditory re-afferentation and particularly that allow recovery of language function. The first aim of this project is to identify the cortical networks, the activity of which varies during the recovery of language function using positron emission tomography (PET). Generally, the language function is completely restored 18 months after implantation. The first study is a longitudinal investigation in which patients will undergo a brain imaging examination the day of the implant onset, and another one 14 months later when the language recovering process will be well engaged and almost optimal. The second aim of this project is to identify cortical networks involved in different speech recognition strategies used by cochlear implanted subjects (global versus phonological) and to compare these networks with those involved in speech recognition in normal subjects. The last question consists in determining whether patients process their new language rather like a native language or like a second language. In the first case, implant would re-activate the ancient nervous pathways used before deafness and in the second case, new circuits would be involved in the processing of the re-built language. To answer this question, the localization and the widespread of cortical areas involved in the processing of different languages (English, their native language, French, a language they learned at school prior to deafness and Norwegian a completely unknown language) will be compared in normal subjects and in patients.
Training content (objective, benefit and expected impact)
Training will consist in acquiring an excellent knowledge in functional neuroanatomy applied to the domain of language and to practice brain imaging techniques, essentially positron emission tomography, but also functional MRI with patients wearing new implant MRI-compatible (without metallic component). After the post-doctoral training period, my objective is to be recruited by the French CNRS, in the laboratory where my PhD was achieved, to work as a researcher, in a cochlear implant team. The projected study is of great importance because, the human cochlear implant model represents the unique way of investigating cortical plasticity associated with the recovery of an essential brain function, the use of language.
Links with industry / industrial relevance (22)