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Poster A45, Wednesday, November 8, 10:30 – 11:45 am, Harborview and Loch Raven Ballrooms

The cognitive and neural oscillatory mechanisms underlying the facilitating effect of rhythm on speech comprehension

Xiaoqing Li1, Jinyan Xia1;1Key Laboratory of Behavioral Science, Institute of Psychology, Chinese Academy of Sciences (Beijing, China)

One of the most fascinating abilities of the human brain is that it can recognize the temporally regular patterns in the dynamically changing auditory or visual stimuli. Quite a lot of studies have demonstrated that temporal prediction derived from the rhythm regularity plays an important role in auditory/visual perception and language comprehension as well. Although the existing studies provide some insights on how temporal prediction affects auditory/sensory perception, the mechanism by which temporal regularity influences language comprehension remains to be explored. The aim of the present study was to use the EEG (electroencephalograph) technique to examine the effect of rhythm regularity on Mandarin Chinese speech comprehension and the internal mechanisms underlying this effect. Specifically, this study aimed to explore, during speech comprehension, how the different stages of language processing (early sensory stage and late semantic stage of information processing) are affected by temporal predictions generated from rhythm regularity, and what’s the neural oscillatory mechanism underlying this rhythm regularity effect. Participants listened to Mandarin Chinese sentences that had a regular or irregular rhythm context and that contained critical nouns that were congruent or incongruent with the sentence contexts. The results revealed that: 1) relative to congruent nouns, incongruent nouns elicited a larger complex of N1+N400+residual N400 in the context of regular rhythm, but elicited only a larger later P600 in the context of irregular rhythm, which suggests that regular rhythm speeds up speech comprehension; moreover, the reduced N1 and N400 indicates that rhythm regularity affects speech comprehension by modulating both the later semantic stage of processing and the early sensory/phonological stage of processing. 2) as compared to irregular rhythm, regular rhythm induced power increases in beta band immediately preceding the critical nouns and power increases in alpha band immediately following the critical nouns; this alpha-power-increase rhythm regularity effect was positively correlated with the N1 enhancement effect (incongruent vs. congruent noun) and the beta-power-increase rhythm regularity effect negatively correlated with the N400 and residual-N400 enhancement effect (incongruent vs. congruent noun) in the regular rhythm context. These correlation effects indicated that the facilitating effect of rhythm regularity on speech comprehension relies at least in part on the beta- and alpha-bands of neural oscillatory activities, and that rhythm regularity facilitates speech comprehension both by enhancing neural excitability associated with early sensory/phonological processing and by reducing cognitive costs associated with later semantic processing. In summary, the present study provides further experimental evidence for the dynamic attending theory by showing that, even during complex spoken sentence comprehension, both the later semantic processing and the very early sensory/phonological processing is modulated by the relatively long-distance rhythm structure of speech sequences. Moreover, the present results also permit us to gain some understanding of the neural oscillatory mechanisms by which rhythm regularity affects speech comprehension. Key words: rhythm regularity; speech comprehension; brain oscillations; dynamic attending theory

Topic Area: Meaning: Prosody, Social and Emotional Processes

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