The Effect of Noise on Cortical Auditory Evoked Potential in Cochlear Implant Users

Abstract

Purpose Cochlear implant (CI) users typically complain of impaired ability to understand speech in noise. Previous studies indicate that the detrimental effects of noise can be measured by the change of neural activities. The current study examined the noise effect on psychoacoustic measures while at the same time used cortical evoked potentials to quantify the change of neural processing of speech sounds caused by noise. Methods Ten adult CI users and fourteen normal-hearing subjects were participated in this study. Cortical auditory evoked potentials (CAEPs) were recorded from 64 scalp electrodes in both quiet and noise conditions each during passive and active listening. Speech stimuli were synthesized consonant-vowels with 0 ms and 50 ms voice onset time (VOT). N1/P2 amplitudes and latencies were analyzed as a function of VOT and listening condition. Behavioral measures as well as a variety of speech perception tasks were conducted. Results For good CI users, speech perception scores in noise condition significantly decreased compared to those in quiet condition for most speech perception tasks. N1 and P2 latencies became prolonged with noise masking compared to the quiet condition. However, unlike what we expected, attentional modulation of CAEPs was not revealed in noise listening. The P2 latency measures were correlated with vowel and consonant perception in noise. Conclusion The effects of noise masking on temporal processing can be reflected in cortical responses in CI users. These results suggest that N1/P2 measures to VOT stimuli with noise masking may represent the change of neural activities in challenging listening situations. Key Words: Cochlear implants, Speech perception in noise, Cortical auditory evoked potentials, Voice onset time 중심 단어: 인공와우, 소음하 ë§ì§€ê°ë ¥, 대뇌피질 청성 ìœ ë°œì „ìœ„, 음성 개시 시간