Han Ji-Hye, Dimitrijevic Andrew
Communication Sciences Research Center, Cincinnati Childs Hospital Medical Center, Cincinnati, OH, United States.
Laboratory of Brain & Cognitive Sciences for Convergence Medicine, College of Medicine, Hallym University, Chuncheon, South Korea.
Front Neurosci. 2020 Feb 18;14:124. doi: 10.3389/fnins.2020.00124. eCollection 2020.
The ability to understand speech is highly variable in people with cochlear implants (CIs) and to date, there are no objective measures that identify the root of this discrepancy. However, behavioral measures of temporal processing such as the temporal modulation transfer function (TMTF) has previously found to be related to vowel and consonant identification in CI users. The acoustic change complex (ACC) is a cortical auditory-evoked potential response that can be elicited by a "change" in an ongoing stimulus. In this study, the ACC elicited by amplitude modulation (AM) change was related to measures of speech perception as well as the amplitude detection threshold in CI users.
Ten CI users (mean age: 50 years old) participated in this study. All subjects participated in behavioral tests that included both speech and amplitude modulation detection to obtain a TMTF. CI users were categorized as "good" ( = 6) or "poor" ( = 4) based on their speech-in noise score (<50%). 64-channel electroencephalographic recordings were conducted while CI users passively listened to AM change sounds that were presented in a free field setting. The AM change stimulus was white noise with four different AM rates (4, 40, 100, and 300 Hz).
Behavioral results show that AM detection thresholds in CI users were higher compared to the normal-hearing (NH) group for all AM rates. The electrophysiological data suggest that N1 responses were significantly decreased in amplitude and their latencies were increased in CI users compared to NH controls. In addition, the N1 latencies for the poor CI performers were delayed compared to the good CI performers. The N1 latency for 40 Hz AM was correlated with various speech perception measures.
Our data suggest that the ACC to AM change provides an objective index of speech perception abilities that can be used to explain some of the variation in speech perception observed among CI users.
人工耳蜗（CI）使用者的言语理解能力差异很大，迄今为止，尚无客观指标能够找出这种差异的根源。然而，先前已发现诸如时间调制传递函数（TMTF）等时间处理的行为指标与CI使用者的元音和辅音识别有关。听觉变化复合波（ACC）是一种皮质听觉诱发电位反应，可由持续刺激中的“变化”诱发。在本研究中，由幅度调制（AM）变化诱发的ACC与CI使用者的言语感知指标以及幅度检测阈值相关。
10名CI使用者（平均年龄：50岁）参与了本研究。所有受试者均参加了行为测试，包括言语和幅度调制检测，以获得TMTF。根据他们在噪声中的言语得分（<50%），CI使用者被分为“良好”（=6）或“较差”（=4）两组。当CI使用者在自由声场环境中被动聆听AM变化声音时，进行了64通道脑电图记录。AM变化刺激是具有四种不同AM率（4、40、100和300Hz）的白噪声。
行为结果表明，在所有AM率下，CI使用者的AM检测阈值均高于正常听力（NH）组。电生理数据表明，与NH对照组相比，CI使用者的N1反应幅度显著降低，潜伏期延长。此外，较差的CI使用者的N1潜伏期比良好的CI使用者延迟。40Hz AM的N1潜伏期与各种言语感知指标相关。
我们的数据表明，对AM变化的ACC提供了言语感知能力的客观指标，可用于解释CI使用者中观察到的言语感知的一些差异。
