Neurophysiological requirements for implanted cochlear prostheses.

Regarding the neurophysiological requirements for implanted cochlear prostheses, we have discussed (i) the complexity of speech sounds, (ii) problems of intensity, then (iii) the frequency problem, and (iv) finally the possibility of a frequency transposition to the genuine frequency range of a single fibre of any mechanoreceptor and its connecting nerve fibre (less than 1 kHz) for the construction of an intracochlear prosthesis. In general it would seem necessary to seek compromises based on the fact that speech, at least the vowels, contains redundancy and that the use of additional sensory channels might be helpful for cochlear implants. Certainly besides other preprocessing techniques for speech information, the multichannel stimulation set-up of special electrodes has to be used to convey a sufficient amount of speech information to restore the faculty of speech perception in completely deaf patients. Decompression of intensity range and compression of frequency range might be especially useful.