Han Ji-Hye, Lee Jihyun, Lee Hyo-Jeong
Laboratory of Brain and Cognitive Sciences for Convergence Medicine, Anyang, Korea.
Department of Otorhinolaryngology-Head and Neck Surgery, Hallym University College of Medicine, Chuncheon, Korea.
Clin Exp Otorhinolaryngol. 2020 Aug;13(3):241-248. doi: 10.21053/ceo.2019.01081. Epub 2020 Jan 7.
Cochlear implant (CI) users typically report impaired ability to understand speech in noise. Speech understanding in CI users decreases with noise due to reduced temporal processing ability, and speech perceptual errors involve stop consonants distinguished by voice onset time (VOT). The current study examined the effects of noise on various speech perception tests while at the same time used cortical auditory evoked potentials (CAEPs) to quantify the change of neural processing of speech sounds caused by noise. We hypothesized that the noise effects on VOT processing can be reflected in N1/P2 measures, the neural changes relate to behavioral speech perception performances.
Ten adult CI users and 15 normal-hearing (NH) people participated in this study. CAEPs were recorded from 64 scalp electrodes in both quiet and noise (signal-to-noise ratio +5 dB) and in passive and active (requiring consonant discrimination) listening. Speech stimulus was synthesized consonant-vowels with VOTs of 0 and 50 ms. N1-P2 amplitudes and latencies were analyzed as a function of listening condition. For the active condition, the P3b also was analyzed. Behavioral measures included a variety of speech perception tasks.
For good performing CI users, performance in most speech test was lower in the presence of noise masking. N1 and P2 latencies became prolonged with noise masking. The P3b amplitudes were smaller in CI groups compared to NH. The degree of P2 latency change (0 vs. 50 ms VOT) was correlated with consonant perception in noise.
The effects of noise masking on temporal processing can be reflected in cortical responses in CI users. N1/P2 latencies were more sensitive to noise masking than amplitude measures. Additionally, P2 responses appear to have a better relationship to speech perception in CI users compared to N1.
人工耳蜗（CI）使用者通常报告在噪声环境中理解言语的能力受损。由于时间处理能力下降，CI使用者在噪声环境中的言语理解能力会降低，并且言语感知错误涉及通过语音起始时间（VOT）区分的塞音。本研究考察了噪声对各种言语感知测试的影响，同时使用皮层听觉诱发电位（CAEP）来量化噪声引起的语音神经处理变化。我们假设噪声对VOT处理的影响可以在N1/P2测量中得到反映，神经变化与行为言语感知表现相关。
10名成年CI使用者和15名听力正常（NH）者参与了本研究。在安静和噪声环境（信噪比+5dB）以及被动和主动（需要辅音辨别）聆听条件下，从64个头皮电极记录CAEP。言语刺激为合成的辅音-元音，VOT分别为0和50毫秒。分析N1-P2波幅和潜伏期作为聆听条件的函数。对于主动条件，还分析了P3b。行为测量包括各种言语感知任务。
对于表现良好的CI使用者，在噪声掩蔽情况下，大多数言语测试的表现较低。噪声掩蔽时N1和P2潜伏期延长。与NH组相比，CI组的P3b波幅较小。P2潜伏期变化程度（0与50毫秒VOT）与噪声中的辅音感知相关。
噪声掩蔽对时间处理的影响可以在CI使用者的皮层反应中得到反映。N1/P2潜伏期比波幅测量对噪声掩蔽更敏感。此外，与N1相比，P2反应似乎与CI使用者的言语感知有更好的关系。
