Acoustic change complex for frequency changes

Purpose: Acoustic change complex (ACC) reflects brain’s capacity to discriminate the acoustic features present in the signal, hence serves as an index of discrimination capacity. ACC for intensity changes and gaps-in-noise have consistently shown that the ACC threshold is consistent with behavioral intensity discrimination and gap detection thresholds. While, the ACC threshold for frequency change is found to be highly variable. The present study was carried out to investigate the agreement between behavioral frequency discrimination threshold and the ACC threshold for frequency change. Methods: Ten young adults with normal hearing in both ears participated in the study. The ACC was elicited using frequency changing tones, with a frequency change of 5, 10, 25, 50, 100 and 200 Hz. Results: The present study showed that a greater frequency change is required to elicit the ACC compared to behavioral discrimination threshold. In most of the participants, a frequency change greater than 50 Hz was required to elicit the ACC. Magnitude of frequency change had effect on latency and amplitude of peaks of the ACC, amplitude was higher and latency was shorter for greater frequency change. Conclusion: ACC threshold for frequency change does not resemble behavioral discrimination threshold and is variable across participants.