Auditory prostheses--a challenge for neurophysiology.
To achieve speech discrimination with prosthetic stimulation, pre-processing of speech adapted to the function to be replaced is indispensable. This is demonstrated using the example of a phase-conserving frequency transposition for a more efficient use of residual hearing. The intelligibility of transposed speech was investigated by employing simulated residual hearing. Long-term implanted electrodes in the auditory nerve of the cat permitted both the measurement of the natural activity of fibres and the application of corresponding stimulus currents. Phase reversal of the acoustic input was used to isolate a phasic response with a topographically differing proportional or differential behaviour. This suggests a periodicity analysis of the sound in the auditory pathway. In acoustic and electrical stimulation, additionally implanted, cortical control electrodes revealed largely corresponding potentials; the dynamic stimulation ranges, however, differed greatly. Finally, the possibility of assessing speech perception by measuring speech-evoked potentials is discussed.
D003054:Cochlear Implants; D004558:Electric Stimulation; D005072:Evoked Potentials, Auditory; D006801:Humans; D013067:Speech Perception / Q000502:physiology*; D000159:Vestibulocochlear Nerve / Q000502:physiology