Department of Psychology, University of Oslo, Oslo, Norway.
RITMO Centre for Interdisciplinary Studies in Rhythm, Time and Motion, University of Oslo, Oslo, Norway.
Sci Rep. 2020 May 14;10(1):7975. doi: 10.1038/s41598-020-64758-y.
The brain responds to violations of expected rhythms, due to extraction- and prediction of the temporal structure in auditory input. Yet, it is unknown how probability of rhythm violations affects the overall rhythm predictability. Another unresolved question is whether predictive processes are independent of attention processes. In this study, EEG was recorded while subjects listened to rhythmic sequences. Predictability was manipulated by changing the stimulus-onset-asynchrony (SOA deviants) for given tones in the rhythm. When SOA deviants were inserted rarely, predictability remained high, whereas predictability was lower with more frequent SOA deviants. Dichotic tone-presentation allowed for independent manipulation of attention, as specific tones of the rhythm were presented to separate ears. Attention was manipulated by instructing subjects to attend to tones in one ear only, while keeping the rhythmic structure of tones constant. The analyses of event-related potentials revealed an attenuated N1 for tones when rhythm predictability was high, while the N1 was enhanced by attention to tones. Bayesian statistics revealed no interaction between predictability and attention. A right-lateralization of attention effects, but not predictability effects, suggested potentially different cortical processes. This is the first study to show that probability of rhythm violation influences rhythm predictability, independent of attention.
大脑会对违反预期节奏的情况做出反应，这是由于对听觉输入中的时间结构进行了提取和预测。然而，目前尚不清楚节奏违规的概率如何影响整体节奏的可预测性。另一个悬而未决的问题是，预测过程是否独立于注意过程。在这项研究中，当被试听节奏序列时记录了 EEG。通过改变节奏中给定音的刺激起始时距（SOA 偏差）来操纵可预测性。当 SOA 偏差很少插入时，可预测性仍然很高，而当 SOA 偏差更频繁时，可预测性较低。双声道音呈现允许独立地操纵注意力，因为节奏中的特定音被呈现到不同的耳朵。通过指示被试只注意一只耳朵中的音，同时保持音的节奏结构不变来操纵注意力。事件相关电位的分析显示，当节奏可预测性高时，音的 N1 会减弱，而当注意力集中在音上时，N1 会增强。贝叶斯统计显示，可预测性和注意力之间没有相互作用。注意力效应的右偏侧化，而不是可预测性效应，表明可能存在不同的皮质过程。这是第一项表明节奏违规概率影响节奏可预测性的研究，且这种影响独立于注意力。
