ExpORL, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium
ExpORL, Department of Neurosciences, KU Leuven, 3000 Leuven, Belgium.
J Neurosci. 2021 Dec 15;41(50):10316-10329. doi: 10.1523/JNEUROSCI.0812-21.2021. Epub 2021 Nov 3.
When listening to speech, our brain responses time lock to acoustic events in the stimulus. Recent studies have also reported that cortical responses track linguistic representations of speech. However, tracking of these representations is often described without controlling for acoustic properties. Therefore, the response to these linguistic representations might reflect unaccounted acoustic processing rather than language processing. Here, we evaluated the potential of several recently proposed linguistic representations as neural markers of speech comprehension. To do so, we investigated EEG responses to audiobook speech of 29 participants (22 females). We examined whether these representations contribute unique information over and beyond acoustic neural tracking and each other. Indeed, not all of these linguistic representations were significantly tracked after controlling for acoustic properties. However, phoneme surprisal, cohort entropy, word surprisal, and word frequency were all significantly tracked over and beyond acoustic properties. We also tested the generality of the associated responses by training on one story and testing on another. In general, the linguistic representations are tracked similarly across different stories spoken by different readers. These results suggests that these representations characterize the processing of the linguistic content of speech. For clinical applications, it would be desirable to develop a neural marker of speech comprehension derived from neural responses to continuous speech. Such a measure would allow for behavior-free evaluation of speech understanding; this would open doors toward better quantification of speech understanding in populations from whom obtaining behavioral measures may be difficult, such as young children or people with cognitive impairments, to allow better targeted interventions and better fitting of hearing devices.
当我们聆听演讲时，大脑会对刺激中的声学事件做出时间锁定反应。最近的研究还报告称，皮质反应会跟踪语言对言语的表示。然而，在描述这些表示的跟踪时，通常不考虑声学特性。因此，对这些语言表示的反应可能反映了未被解释的声学处理，而不是语言处理。在这里，我们评估了几种最近提出的语言表示作为言语理解神经标记的潜力。为此，我们研究了 29 名参与者（22 名女性）对有声读物语音的 EEG 反应。我们研究了这些表示是否在控制声学特性后提供了独特的信息，而不仅仅是声学神经跟踪和彼此之间的信息。事实上，并非所有这些语言表示在控制声学特性后都得到了显著的跟踪。然而，音位意外、语料库熵、单词意外和单词频率都在控制声学特性后得到了显著的跟踪。我们还通过在一个故事上进行训练并在另一个故事上进行测试来测试相关反应的通用性。总的来说，这些语言表示在不同读者讲述的不同故事中都得到了相似的跟踪。这些结果表明，这些表示特征化了言语语言内容的处理。对于临床应用，最好从对连续言语的神经反应中开发言语理解的神经标记。这样的测量方法将允许对言语理解进行无行为评估；这将为从难以获得行为测量的人群（如幼儿或认知障碍者）中更好地量化言语理解打开大门，以便更好地进行有针对性的干预和更好地适应听力设备。
