Long-term auditory adaptation to a modified peripheral frequency map

Abstract

Cochlear implants (CIs) attempt to mimic the tonotopicity of the normal ear by stimulating more basal regions of the cochlea in response to higher frequencies. However, there may be a mismatch between the normal place-frequency map and that implemented by a CI. Aiming to measure this potential mismatch and its changes over time, the present study used a method-of-adjustment procedure where CI users and normal-hearing listeners selected synthetic vowels to match prespecified vowel targets. Data from CI users were obtained longitudinally, starting on the day of initial stimulation and continuing for 2 years. CI users showed a significant amount of initial mismatch with respect to the normal-hearing listeners, but they also showed significant learning and adaptation over time and achieved nearly normal performance after some experience with the CI. In general, the adaptation process took several months, suggesting that some CI users may benefit from alternative signal processing or rehabilitation procedures designed to facilitate perceptual learning after cochlear implantation.