Mismatch negativity brain response as an index of speech perception recovery in cochlear-implant recipients.

Speech-discrimination performance and the mismatch negativity (MMN) response elicited by vowel changes were used to track vowel-perception improvement of 5 adult cochlear-implant (CI) recipients. The MMN was recorded several times during the first 3 years after CI activation. Artefacts, presumably caused by CI, contaminated most of the brain responses until 1 year after CI activation. We found that speech discrimination improved over time and the MMN, observed in all patients after 2.5 years of CI use, was first seen for the larger vowel difference and later for the smaller one.