Abstract：
Decoding human speech requires the brain to segment the incoming acoustic signal into meaningful linguistic units, ranging from syllables and words to phrases. Integrating these linguistic constituents into a coherent percept sets the root of compositional meaning and hence understanding. One important cue for segmentation in natural speech is prosodic cues, such as pauses, but their interplay with higher-level linguistic processing is still unknown. Here, we dissociate the neural tracking of prosodic pauses from the segmentation of multi-word chunks using magnetoencephalography (MEG). We find that manipulating the regularity of pauses disrupts slow speech-brain tracking bilaterally in auditory areas (below 2 Hz) and in turn increases left-lateralized coherence of higher-frequency auditory activity at speech onsets (around 25-45 Hz). Critically, we also find that multi-word chunks-defined as short, coherent bundles of inter-word dependencies-are processed through the rhythmic fluctuations of low-frequency activity (below 2 Hz) bilaterally and independently of prosodic cues. Importantly, low-frequency alignment at chunk onsets increases the accuracy of an encoding model in bilateral auditory and frontal areas while controlling for the effect of acoustics. Our findings provide novel insights into the neural basis of speech perception, demonstrating that both acoustic features (prosodic cues) and abstract linguistic processing at the multi-word timescale are underpinned independently by low-frequency electrophysiological brain activity in the delta frequency range.
摘要：
解码人类语音需要大脑将传入的声音信号分割为有意义的语言单位，从音节和单词到短语。将这些语言成分整合到连贯的感知中，是构成意义和理解的根源。自然语音中分割的一个重要线索是韵律线索，如停顿，但是它们与高级语言处理的相互作用仍然未知。这里,我们使用脑磁图（MEG）将韵律停顿的神经跟踪与多词块的分割分离。我们发现，操纵停顿的规律性会破坏听觉区域（低于2Hz）的双向缓慢的语音-大脑跟踪，进而增加语音开始时（约25-45Hz）的高频听觉活动的左侧连贯性。严重的,我们还发现多词块定义为短，单词间依赖关系的连贯束-通过低频活动（低于2Hz）的节律波动进行双边处理，并且与韵律提示无关。重要的是,在块起始时的低频对齐增加了双侧听觉和额叶区域中编码模型的准确性，同时控制了声学效果。我们的发现为言语感知的神经基础提供了新的见解，证明了在多字时间尺度上的声学特征（韵律提示）和抽象语言处理都是由增量频率范围内的低频电生理大脑活动独立支撑的。
