Data from: Perceptually relevant speech tracking in auditory and motor cortex reflects distinct linguistic features

During online speech processing, our brain tracks the acoustic fluctuations in speech at different timescales. Previous research has focused on generic timescales (for example, delta or theta bands) that are assumed to map onto linguistic features such as prosody or syllables. However, given the high intersubject variability in speaking patterns, such a generic association between the timescales of brain activity and speech properties can be ambiguous. Here, we analyse speech tracking in source-localised magnetoencephalographic data by directly focusing on timescales extracted from statistical regularities in our speech material. This revealed widespread significant tracking at the timescales of phrases (0.6–1.3 Hz), words (1.8–3 Hz), syllables (2.8–4.8 Hz), and phonemes (8–12.4 Hz). Importantly, when examining its perceptual relevance, we found stronger tracking for correctly comprehended trials in the left premotor (PM) cortex at the phrasal scale as well as in left middle temporal cortex at the word scale. Control analyses using generic bands confirmed that these effects were specific to the speech regularities in our stimuli. Furthermore, we found that the phase at the phrasal timescale coupled to power at beta frequency (13–30 Hz) in motor areas. This cross-frequency coupling presumably reflects top-down temporal prediction in ongoing speech perception. Together, our results reveal specific functional and perceptually relevant roles of distinct tracking and cross-frequency processes along the auditory–motor pathway.

在在线言语处理过程中，人类大脑会在不同时间尺度上追踪言语的声学波动。过往研究多聚焦于通用时间尺度（例如delta频段或theta频段），这类尺度被认为与韵律、音节等语言特征存在映射关系。然而，由于说话模式存在显著的个体间差异，大脑活动时间尺度与言语属性之间的这类通用关联可能存在歧义。本研究通过直接聚焦于从言语材料的统计规律中提取的时间尺度，对源定位的脑磁图（magnetoencephalographic, MEG）数据中的言语追踪现象进行分析。结果显示，在短语（0.6–1.3 Hz）、单词（1.8–3 Hz）、音节（2.8–4.8 Hz）以及音素（8–12.4 Hz）对应的时间尺度上，存在广泛且显著的追踪效应。值得注意的是，在考察其感知相关性时，我们发现，在短语尺度下左侧前运动皮层（premotor cortex, PM）以及单词尺度下左侧颞中皮层中，被试正确理解的试次具有更强的追踪效应。采用通用频段进行的对照分析证实，这些效应仅与本研究刺激中的言语统计规律相关。此外，我们还发现，运动皮层内的短语时间尺度相位与beta频段（13–30 Hz）的功率存在耦合。这种跨频率耦合可能反映了持续言语感知中的自上而下的时间预测机制。综上，本研究结果揭示了听觉-运动通路中不同的追踪与跨频率过程所具备的特异性功能及感知相关作用。