Deoisres Suwijak, Aljarboa Ghadah S, Bell Steven L, Simpson David M
Institute of Sound and Vibration Research, University of Southampton, Southampton, United Kingdom.
Institute of Sound and Vibration Research, University of Southampton, Southampton, United Kingdom.
Hear Res. 2025 Mar;457:109197. doi: 10.1016/j.heares.2025.109197. Epub 2025 Jan 15.
The cortical tracking of the acoustic envelope is a phenomenon where the brain's electrical activity, as recorded by electroencephalography (EEG) signals, fluctuates in accordance with changes in stimulus intensity (the acoustic envelope of the stimulus). Understanding speech in a noisy background is a key challenge for people with hearing impairments. Speech stimuli are therefore more ecologically valid than clicks, tone pips, or speech tokens (e.g., syllables) for assessing hearing. However, it remains unclear whether EEG responses to speech provide an advantage in predicting speech intelligibility. This study aimed to assess the ability of cortical responses to speech and speech-related sounds to predict behavioural speech-in-noise performance in listeners with normal hearing when they are not attending to the stimuli. Twenty native English-speaking adults with normal hearing (aged 18 to 40 years) participated in a speech reception task, listening to English Matrix sentences presented at signal-to-noise ratios (SNRs) of -15, -10, -5, 0, and ∞ (no background noise) dB, and then identifying the words they heard in the sentences. In the EEG experiment, the participants then listened to continuous speech, broadband noise modulated by the envelope of speech, and repeating short /da/ stimuli presented at the same SNR levels as in the Matrix test. For the latter, Auditory Late Response (ALR) was estimated from the EEG, and for the former, the strength of the envelope-tracking responses was calculated. Cortical responses to all stimuli showed monotonic relationships with the signal-to-noise ratio at the group level and in most individuals, although there was considerable variability. EEG analysis in the delta band showed no significant difference in the number of participants with predicted speech reception thresholds (SRTs) within an error margin of 7 dB-the level at which SRT prediction is considered applicable-regardless of the type of cortical response used. In the theta band, however, SRT predictions based on cortical responses to continuous speech performed worse, showing a significantly lower number of predictions within an error margin of 7 dB compared to those based on cortical responses to modulated noise and the repeating /da/ sound. The proportion of individual SRT predictions with an error margin within 7 dB was, at best, 30 %. For people with normal hearing, cortical responses to continuous speech and modulated noise predicted speech-in-noise performance at the group level but not at the individual level, due to variability in cortical tracking of the acoustic envelope. Predicting the SRT on an individual level remains a major and clinically important challenge.
听觉包络的皮层追踪是一种现象，即通过脑电图（EEG）信号记录的大脑电活动会根据刺激强度（刺激的听觉包络）的变化而波动。在嘈杂背景中理解言语是听力障碍者面临的一项关键挑战。因此，对于评估听力而言，言语刺激比咔哒声、纯音或言语片段（如音节）在生态学上更具效度。然而，EEG对言语的反应是否在预测言语可懂度方面具有优势仍不清楚。本研究旨在评估皮层对言语及与言语相关声音的反应，以预测听力正常的听众在不关注刺激时的噪声中言语行为表现。20名以英语为母语、听力正常的成年人（年龄在18至40岁之间）参与了一项言语接收任务，他们听以-15、-10、-5、0和∞（无背景噪声）分贝的信噪比呈现的英语矩阵句子，然后识别句子中听到的单词。在EEG实验中，参与者随后听连续言语、由言语包络调制的宽带噪声，以及以与矩阵测试相同的信噪比水平呈现的重复短音/da/刺激。对于后者，从EEG中估计听觉晚期反应（ALR），对于前者，计算包络追踪反应的强度。在群体水平和大多数个体中，对所有刺激的皮层反应均与信噪比呈单调关系，尽管存在相当大的变异性。在δ频段的EEG分析显示，无论使用何种皮层反应类型，在预测言语接收阈值（SRT）的误差范围在7分贝以内（即认为SRT预测适用的水平）的参与者数量上没有显著差异。然而，在θ频段，基于对连续言语的皮层反应的SRT预测表现较差，与基于对调制噪声和重复/da/声音的皮层反应相比，在7分贝误差范围内的预测数量显著减少。个体SRT预测误差范围在7分贝以内的比例最高为30%。对于听力正常的人来说，由于听觉包络的皮层追踪存在变异性，皮层对连续言语和调制噪声的反应在群体水平上能预测噪声中言语表现，但在个体水平上则不然。在个体水平上预测SRT仍然是一项重大且具有临床重要性的挑战。
