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要旨

Temporal prediction assists language comprehension. In a series of recent behavioral studies, we have shown that listeners specifically employ rhythmic modulations of prosody to estimate the duration of upcoming sentences, thereby speeding up comprehension. In the current human magnetoencephalography (MEG) study on participants of either sex, we show that the human brain achieves this function through a mechanism termed entrainment. Through entrainment, electrophysiological brain activity maintains and continues contextual rhythms beyond their offset. Our experiment combined exposure to repetitive prosodic contours with the subsequent presentation of visual sentences that either matched or mismatched the duration of the preceding contour. During exposure to prosodic contours, we observed MEG coherence with the contours, which was source-localized to right-hemispheric auditory areas. During the processing of the visual targets, activity at the frequency of the preceding contour was still detectable in the MEG; yet sources shifted to the (left) frontal cortex, in line with a functional inheritance of the rhythmic acoustic context for prediction. Strikingly, when the target sentence was shorter than expected from the preceding contour, an omission response appeared in the evoked potential record. We conclude that prosodic entrainment is a functional mechanism of temporal prediction in language comprehension. In general, acoustic rhythms appear to endow language for employing the brain's electrophysiological mechanisms of temporal prediction.

Significance statement Language comprehension benefits from our ability to predict upcoming stimuli. Here, we report on a key neural substrate. We show that electrophysiological brain activity inherits prosodic modulations—the melody of speech—from prior context, allowing listeners to estimate the duration of upcoming language stimuli: By using magnetoencephalography, we find that the brain not only responds to prosody when speech is present, but its activity continues at the prosodic frequency seconds into the future, benefiting behavioral responses. During continuation, activity shifts from auditory to frontal cortex, the epicenter of the brain's predictive abilities. The human brain seems to initiate the top-down prediction of language stimuli by copying sensory rhythms and projecting them into the future.