Uyaran İçerisindeki Akustik Komponentlerin Akustik Değişim Kompleksi Cevabına Katkısı

Abstract

Acoustic change complex (ACC) is a cortical auditory evoked potential in response to a change in a sustained sound. The ACC response evoked by the /ui/ stimulus arise from the onset of the /i/ sound and the F2 formant frequency change that occurs during the transition from /u/ to /i/, but which of these two acoustic events has more effect on the response has not been investigated before. The present study was conducted to investigate the contribution of these two acoustic events to the ACC response. A total of 21 volunteers, 11 females and 10 males, aged 18-30 years, who did not have any psychiatric and neurological problems, no noise exposure, and no hearing pathology, who were not professionally involved in instrumental music, participated in the study. In the study, the /ui/ stimulus was presented in 3 different background conditions: silent condition and +5 dB SNR, masked condition and filtered masked (2400 Hz high-pass frequency) condition. Repeated measures analysis of variance was performed to compare ACC N1 latency values and ACC N1-P2 peak-to-peak amplitudes between conditions. As a result of pairwise comparisons, it was seen that ACC N1 latencies were significantly higher in the filtered masked condition than in the silent condition and the masked condition (p = .038 and p = .022, respectively). In terms of amplitude values, in pairwise comparisons, the filtered masked condition was found to be significantly lower than ACC N1-P2 and the masked condition. (p= .000). There was no statistically significant difference in latency and amplitude between the silent condition and the masked condition. In this respect, the condition in which the /i/ sound was selectively masked was the condition in which the response amplitudes and latencies were significantly affected. The results suggest that the onset of the /i/ sound is the basic acoustic feature that evokes the ACC N1 response evoked by the /ui/ stimulus. In future studies, it may be recommended to use behaviorally determined mask levels, masking filter frequencies and to create more challenging listening conditions.