Functional Organization of the Auditory Cortex in the Congenitally Deaf White Cat
Cochlear-implants have developed to the most successful neuroprosthesis. In most cases patients benefit substantially from such a device. However, there is one important exception, the implantation of prelingually deaf adults. In these patients the results are disappointing. The reason for this can be easily hypothesised: During early childhood the central auditory system has to acquire strategies for the evaluation of sound stimuli in general and for the processing in language in particular. It is assumed that these processes of central auditory maturation have to take place within certain time-windows, so called critical periods and that later on a deficit is beyond recovery. Consequently the results of cochlear implantation in prelingually deaf children are substantially more successful (Lehnhardt and Bertram, 1991; Lenarz et al., 1994; Blarney, 1995; Dowell et al., 1995) and at first sight one would have to recommend an early implantation in connatally deaf infants. Obviously such an implantation is not generally possible. There are problems with an early and safe diagnoses of deafness, there are surgical problems with an implantation of a rigid device into a growing head and there will always be cases where a correct early diagnosis was missed by one or the other reason. Thus one would like to know when and how rigid are the critical periods in humans. Is there an age beyond of which an implantation is useless and what is this age?
KeywordsAuditory Cortex Cochlear Implantation Electrode Pair Cortical Response Threshold Curve
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