Cerebral auditory plasticity and cochlear implants

Previous animal research and clinical experiences in humans suggest the exi stence of an auditory critical period in language acquisition. We review th e literature and present the changes within the cochlear nuclei in bilatera lly deafferentated adult non-human primates. We also present and analyse th e results of 98 prelingually deaf children and teenagers who underwent a co chlear implantation at the University of Navarra. Patients received a Nucle us 22 or 24 multichannel cochlear implant (CI). They were grouped in five c ategories according to their age at surgery. Performance is compared with a control group of 58 postlinguals. Only early-implanted prelingual children (before 6 years of age) achieved a complete open-set speech recognition, e ven with better performance than postlinguals. These results clearly demons trate the existence of a period of high neural auditory plasticity within t he first 6 years of life. The introduction of auditory stimulation with a C I can not restore the loss of neural plasticity out of this period. Preling ual children under 6 years of age should receive a CI as soon as there is a reliable diagnosis of bilateral sensorineural hearing loss. (C) 1999 Elsev ier Science Ireland Ltd. All rights reserved.