For postlingually deafened adults to receive maximum benefit from a cochlear Implant, they must adapt to a stimulus that is vastly different from the representations of speech stored in their long-term memory. This issue may be particularly relevant for bilateral cochlear implant users, as they must not only adapt to electrical stimulation of one ear, but also to possible asymmetries between ears. Such asymmetries may be exacerbated by the lack of fitting procedures for bilateral implants, as current clinical care recommends fitting each ear separately with no specific procedure to coordinate the implants so that they work best together. The current proposal focuses on this issue, and describes three experiments to Investigate the optimization of bilateral cochlear Implant fittings, and the effects of between-ear asymmetries. Experiment 1 will test the hypothesis that different procedures for pitch-matching across the two electrode arrays will result in similar adjustments to the frequency table. Experiments 2 will test the hypotheses that pitch- and loudness-matching procedures will enhance speech perception and sound localization abilities in experienced bilateral cochlear implant users. Experiment 3. will test the hypothesis that between-electrode asymmetries can hinder speech understanding, and that the deterioration in performance is exacerbated by stimulation strategies thought to induce narrower patterns of electrical activation.
These experiments will provide valuable public health information with regard to patient outcomes with bilateral cochlear implants, particularly with regard to optimizing their fitting procedures. Furthermore, they will employ innovating techniques to do so which will likely have widespread application for optimizing of cochlear implant fitting, and reducing the time patients require to fully adapt to their cochlear implant(5).
