The Acoustic Change Complex and its Relation to Speech Perception in Cochlear Implant Users

Background: CI users can reach impressive speech perception abilities, however, they show a large variability. The clinical audiometry measures to evaluate their hearing are subjective and require linguistic skills. A cortical auditory evoked potential, like the acoustic change complex (ACC), might be a helpful objective measure, less biased by cognitive skills, to assess their auditory performance.

Objective: To evaluate whether ACC waveform variables are predictive for speech perception in CI users.

Methods: We recorded the ACC in 9 bilaterally and 3 unilaterally deaf adult CI users with more than one year CI experience. The ACC was evoked by a pure tone stimulus directly presented in the center of the frequency band of the medial or apical CI electrode, with frequency changes corresponding to inter-electrode distances (1-3 electrodes). Speech perception was assessed in quiet and in noise.

Results: In all subjects reliable ACCs could be evoked. Increasing frequency changes resulted in increasing N1-P2 amplitudes and decreasing N1 latencies. Speech perception in noise was significantly correlated to the ACC amplitude for each of the two electrode sites (r > 0.6, p < 0.05).

Conclusion: The ACC is a potentially useful objective measure to contribute to better rehabilitation of CI users, as it is a non-attentive test, which correlates with postoperative performance.