1 BRAIN Lab, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, Københavns Universitet2 Department of Media, Cognition and Communication, Faculty of Humanities, Københavns Universitet3 Department of Psychology, Study Council, Department of Psychology, Faculty of Social Sciences, Københavns Universitet4 Center for Functionally Integrative Neuroscience, Aarhus University Hospital, Nørrebrogade 44, Building 10G 6th, 8000 Aarhus C, Denmark ; Royal Academy of Music, Skovgaardsgade 2a, 8000 Aarhus C, Denmark.5 Department of Media, Cognition and Communication, Faculty of Humanities, Københavns Universitet6 BRAIN Lab, Department of Neuroscience and Pharmacology, Faculty of Health and Medical Sciences, Københavns Universitet7 Department of Psychology, Study Council, Department of Psychology, Faculty of Social Sciences, Københavns Universitet
The most dramatic progress in the restoration of hearing takes place in the first months after cochlear implantation. To map the brain activity underlying this process, we used positron emission tomography at three time points: within 14 days, three months, and six months after switch-on. Fifteen recently implanted adult implant recipients listened to running speech or speech-like noise in four sequential PET sessions at each milestone. CI listeners with postlingual hearing loss showed differential activation of left superior temporal gyrus during speech and speech-like stimuli, unlike CI listeners with prelingual hearing loss. Furthermore, Broca's area was activated as an effect of time, but only in CI listeners with postlingual hearing loss. The study demonstrates that adaptation to the cochlear implant is highly related to the history of hearing loss. Speech processing in patients whose hearing loss occurred after the acquisition of language involves brain areas associated with speech comprehension, which is not the case for patients whose hearing loss occurred before the acquisition of language. Finally, the findings confirm the key role of Broca's area in restoration of speech perception, but only in individuals in whom Broca's area has been active prior to the loss of hearing.
Neural Plasticity, 2013, Vol 2013, Issue 318521, p. 1-11