Division of Surgery, Medical School, The University of Western Australia, Perth, Washington, Australia.
Department of Audiology, Fiona Stanley Fremantle Hospitals Group, Perth, Washington, Australia.
Audiol Neurootol. 2023;28(4):280-293. doi: 10.1159/000529485. Epub 2023 Mar 20.
In individuals with single-sided deafness (SSD), who are characterised by profound hearing loss in one ear and normal hearing in the contralateral ear, binaural input is no longer present. A cochlear implant (CI) can restore functional hearing in the profoundly deaf ear, with previous literature demonstrating improvements in speech-in-noise intelligibility with the CI. However, we currently have limited understanding of the neural processes involved (e.g., how the brain integrates the electrical signal produced by the CI with the acoustic signal produced by the normal hearing ear) and how modulation of these processes with a CI contributes to improved speech-in-noise intelligibility. Using a semantic oddball paradigm presented in the presence of background noise, this study aims to investigate how the provision of CI impacts speech-in-noise perception of SSD-CI users.
Task performance (reaction time, reaction time variability, target accuracy, subjective listening effort) and high density electroencephalography from twelve SSD-CI participants were recorded, while they completed a semantic acoustic oddball task. Reaction time was defined as the time taken for a participant to press the response button after stimulus onset. All participants completed the oddball task in three different free-field conditions with the speech and noise coming from different speakers. The three tasks were: (1) CI-On in background noise, (2) CI-Off in background noise, and (3) CI-On without background noise (Control). Task performance and electroencephalography data (N2N4 and P3b) were recorded for each condition. Speech in noise and sound localisation ability were also measured.
Reaction time was significantly different between all tasks with CI-On (M [SE] = 809 [39.9] ms) having faster RTs than CI-Off (M [SE] = 845 [39.9] ms) and Control (M [SE] = 785 [39.9] ms) being the fastest condition. The Control condition exhibited significantly shorter N2N4 and P3b area latency compared to the other two conditions. However, despite these differences noticed in RTs and area latency, we observed similar results between all three conditions for N2N4 and P3b difference area.
The inconsistency between the behavioural and neural results suggests that EEG may not be a reliable measure of cognitive effort. This rationale is further supported by different explanations used in past studies to explain N2N4 and P3b effects. Future studies should look to alternative measures of auditory processing (e.g., pupillometry) to gain a deeper understanding of the underlying auditory processes that facilitate speech-in-noise intelligibility.
在单侧聋（SSD）个体中，由于一只耳朵深度听力损失，而另一只耳朵听力正常，双耳输入不再存在。人工耳蜗（CI）可以恢复深度聋耳的功能性听力，先前的文献表明，CI 可提高语音噪声可懂度。然而，我们目前对涉及的神经过程（例如，大脑如何将 CI 产生的电信号与正常听力耳产生的声信号整合）以及 CI 如何调节这些过程以提高语音噪声可懂度知之甚少。本研究采用语义异常范式，并在背景噪声下进行，旨在研究 CI 对 SSD-CI 用户语音噪声感知的影响。
记录了 12 名 SSD-CI 参与者的任务表现（反应时间、反应时变异性、目标准确性、主观听力努力）和高密度脑电图，同时他们完成了语义听觉异常任务。反应时间定义为参与者在刺激开始后按下响应按钮所需的时间。所有参与者在三种不同的自由场条件下完成了异常任务，语音和噪声来自不同的扬声器。三个任务分别为：（1）CI-On 在背景噪声中，（2）CI-Off 在背景噪声中，和（3）CI-On 无背景噪声（对照）。记录了每个条件下的任务表现和脑电图数据（N2N4 和 P3b）。还测量了语音噪声和声音定位能力。
所有任务中 CI-On（M [SE] = 809 [39.9] ms）的反应时间均显著不同，CI-On 快于 CI-Off（M [SE] = 845 [39.9] ms）和对照（M [SE] = 785 [39.9] ms），对照条件下的反应时间最快。对照条件的 N2N4 和 P3b 区潜伏期明显短于其他两种条件。然而，尽管在 RTs 和区潜伏期上观察到这些差异，但我们在所有三种条件下都观察到 N2N4 和 P3b 差异区的相似结果。
行为和神经结果之间的不一致表明，脑电图可能不是认知努力的可靠测量指标。这一推理得到了过去研究中用于解释 N2N4 和 P3b 效应的不同解释的进一步支持。未来的研究应该寻求替代的听觉处理测量方法（例如，瞳孔测量法），以更深入地了解促进语音噪声可懂度的潜在听觉过程。
