To describe the adaptive pattern of cortically generated auditory evoked potentials elicited by repeated stimuli via cochlear implants (CIs), the late auditory evoked potential (LAEP) was collected from nine postlingually deafened adult CI users. Tone bursts were presented in 30 trains consisting of 10 tone bursts each, with inter-stimulus intervals (ISIs) of 0.7 ms and inter-train intervals (ITIs) of 15s. The response to the first stimulus and the response to later tone bursts in the train were compared. Results showed that the LAEP for the first tone burst was larger than that for later tone bursts, displaying an adaptive pattern. This pattern appeared to be more prominent in CI users with good speech perception performance than in those with poorer performance. This finding is meaningful in the context of our future research to restore normal adaptation in CI users to improve their speech perception performance.

The reduction of latency in the time course of the ALR might be related to the fact that neurons with shorter latencies had faster recovery speed from adaptation and/or refractoriness than those with longer latencies. This finding is meaningful in the context of future research to restore normal adaptation in abnormal hearing populations such as cochlear implant patients.

Our interpretation of these findings is that the faster recovery of the LAEP in CI users is related to abnormal adaptation mechanisms and a less prominent role of the components with longer latencies in the LAEP of CI users. Other mechanisms such as the compromised inhibitory regulation in the auditory system and the aging effect in CI users might also play a role. More research needs to be done to determine whether the slope of the LAEP recovery function is correlated with speech-perception performance.

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