CAN EVENT-RELATED POTENTIALS BE EVOKED BY EXTRA-COCHLEAR STIMULATION AND USED FOR SELECTION PURPOSES IN COCHLEAR IMPLANTATION

To investigate whether electrically evoked event-related responses (P3 00) could be elicited by extracochlear stimulation, measurements were performed on a group of adults fitted with the single-channel extra-co chlear implant. To optimize measurement conditions, and because of the low number of subjects still using an extra-cochlear device in our co chlear implant programme, measurements were also performed on a group of experienced users fitted with the intra-cochlear Nucleus multichann el device. For reference purposes, subjects with normal hearing (contr ol group) were also included in the study. Reproducible late Latency r esponses (N1 and P2 peaks) were found in the five extra-cochlear impla nt users, while P300s were present in four out of these five subjects. The latencies were longer than those of the control group, but were s imilar to those obtained in the intra-cochlear implant group. Signific ant correlations were found for most N1, P2 and P300 measurements evok ed by the tonal stimuli and by speech stimuli. The P300 amplitudes, ev oked by either tonal or speech stimuli, appeared to be related to spee ch perception ability. This led to the conclusion that N1, P2 and P300 measurements may have potential as a clinical tool for preoperative p rediction and postoperative evaluation of sound processing on a cortic al level.