Auditory steady state responses in cochlear implants

oral presentationElectrically Auditory Steady State Responses (EASSRs) are EEG potentials in response to periodic electrical stimuli presented through a cochlear implant (CI). Recently, for slow rate pulse trains in the 40Hz range, the electrophysiological thresholds derived from response amplitude growth functions have been demonstrated to correlate well with behavioral thresholds at these rates. In the following studies we show that auditory steady state potentials can as well be reliably evoked by amplitude-modulated or pulse-width-modulated high-rate pulse trains at clinically used carrier rates, and that stimulus artifacts can be completely removed from the electrophysiological recordings. Multichannel EEG-data have been recorded in Nucleus cochlear implant users. The properties of the resulting responses with regards to amplitude, phase and apparent latency are analyzed. The predictive value of electrophysiological thresholds derived from such responses for behavioral thresholds at these high rates is examined. This objective threshold determination method may be used in future CI fitting paradigms. Support provided by IWT-Vlaanderen project 080304 and Cochlearstatus: publishe