Verschueren Eline, Gillis Marlies, Decruy Lien, Vanthornhout Jonas, Francart Tom
Research Group Experimental Oto-rhino-laryngology, Department of Neurosciences, KU Leuven-University of Leuven, Leuven, 3000, Belgium
Research Group Experimental Oto-rhino-laryngology, Department of Neurosciences, KU Leuven-University of Leuven, Leuven, 3000, Belgium.
J Neurosci. 2022 Sep 28;42(39):7442-7453. doi: 10.1523/JNEUROSCI.0259-22.2022.
When listening to continuous speech, the human brain can track features of the presented speech signal. It has been shown that neural tracking of acoustic features is a prerequisite for speech understanding and can predict speech understanding in controlled circumstances. However, the brain also tracks linguistic features of speech, which may be more directly related to speech understanding. We investigated acoustic and linguistic speech processing as a function of varying speech understanding by manipulating the speech rate. In this paradigm, acoustic and linguistic speech processing is affected simultaneously but in opposite directions: When the speech rate increases, more acoustic information per second is present. In contrast, the tracking of linguistic information becomes more challenging when speech is less intelligible at higher speech rates. We measured the EEG of 18 participants (4 male) who listened to speech at various speech rates. As expected and confirmed by the behavioral results, speech understanding decreased with increasing speech rate. Accordingly, linguistic neural tracking decreased with increasing speech rate, but acoustic neural tracking increased. This indicates that neural tracking of linguistic representations can capture the gradual effect of decreasing speech understanding. In addition, increased acoustic neural tracking does not necessarily imply better speech understanding. This suggests that, although more challenging to measure because of the low signal-to-noise ratio, linguistic neural tracking may be a more direct predictor of speech understanding. An increasingly popular method to investigate neural speech processing is to measure neural tracking. Although much research has been done on how the brain tracks acoustic speech features, linguistic speech features have received less attention. In this study, we disentangled acoustic and linguistic characteristics of neural speech tracking via manipulating the speech rate. A proper way of objectively measuring auditory and language processing paves the way toward clinical applications: An objective measure of speech understanding would allow for behavioral-free evaluation of speech understanding, which allows to evaluate hearing loss and adjust hearing aids based on brain responses. This objective measure would benefit populations from whom obtaining behavioral measures may be complex, such as young children or people with cognitive impairments.
在聆听连续语音时，人类大脑能够追踪呈现的语音信号的特征。研究表明，对声学特征的神经追踪是语音理解的先决条件，并且在可控环境中能够预测语音理解。然而，大脑也会追踪语音的语言特征，这可能与语音理解更直接相关。我们通过操纵语速来研究声学和语言语音处理与不同语音理解能力之间的关系。在这个范式中，声学和语言语音处理同时受到影响，但方向相反：当语速增加时，每秒会有更多的声学信息。相比之下，当语速较高时语音清晰度较低，对语言信息的追踪就变得更具挑战性。我们测量了18名参与者（4名男性）在不同语速下聆听语音时的脑电图。正如预期并得到行为结果证实的那样，语音理解随着语速的增加而下降。相应地，语言神经追踪随着语速的增加而下降，但声学神经追踪增加。这表明对语言表征的神经追踪能够捕捉到语音理解能力下降的渐进影响。此外，声学神经追踪的增加并不一定意味着更好的语音理解。这表明，尽管由于信噪比低而更难测量，但语言神经追踪可能是语音理解的更直接预测指标。一种越来越流行的研究神经语音处理的方法是测量神经追踪。尽管已经对大脑如何追踪声学语音特征进行了大量研究，但语言语音特征受到的关注较少。在本研究中，我们通过操纵语速来区分神经语音追踪的声学和语言特征。一种客观测量听觉和语言处理的恰当方法为临床应用铺平了道路：一种客观的语音理解测量方法将允许在无行为的情况下评估语音理解，这有助于评估听力损失并根据大脑反应调整助听器。这种客观测量方法将使那些获取行为测量可能很复杂的人群受益，例如幼儿或认知障碍患者。
