Evaluating Changes in Adult Cochlear Implant Users' Brain and Behavior Following Auditory Training.

Abstract

To describe the effects of two types of auditory training on both behavioral and physiological measures of auditory function in cochlear implant (CI) users, and to examine whether a relationship exists between the behavioral and objective outcome measures. This study involved two experiments, both of which used a within-subject design. Outcome measures included behavioral and cortical electrophysiological measures of auditory processing. In Experiment I, 8 CI users participated in a music-based auditory training. The training program included both short training sessions completed in the laboratory as well as a set of 12 training sessions that participants completed at home over the course of a month. As part of the training program, study participants listened to a range of different musical stimuli and were asked to discriminate stimuli that differed in pitch or timbre and to identify melodic changes. Performance was assessed before training and at three intervals during and after training was completed. In Experiment II, 20 CI users participated in a more focused auditory training task: the detection of spectral ripple modulation depth. Training consisted of a single 40-minute session that took place in the laboratory under the supervision of the investigators. Behavioral and physiologic measures of spectral ripple modulation depth detection were obtained immediately pre- and post-training. Data from both experiments were analyzed using mixed linear regressions, paired t tests, correlations, and descriptive statistics. In Experiment I, there was a significant improvement in behavioral measures of pitch discrimination after the study participants completed the laboratory and home-based training sessions. There was no significant effect of training on electrophysiologic measures of the auditory N1-P2 onset response and acoustic change complex (ACC). There were no significant relationships between electrophysiologic measures and behavioral outcomes after the month-long training. In Experiment II, there was no significant effect of training on the ACC, although there was a small but significant improvement in behavioral spectral ripple modulation depth thresholds after the short-term training. This study demonstrates that auditory training improves spectral cue perception in CI users, with significant perceptual gains observed despite cortical electrophysiological responses like the ACC not reliably predicting training benefits across short- and long-term interventions. Future research should further explore individual factors that may lead to greater benefit from auditory training, in addition to optimization of training protocols and outcome measures, as well as demonstrate the generalizability of these findings.