Causal cortical dynamics of a predictive enhancement of speech intelligibility
Causal cortical dynamics of a predictive enhancement of speech intelligibility
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DOI：
10.1016/j.neuroimage.2017.10.066
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发表时间：
2018-02-01
期刊：
影响因子：
5.7
通讯作者：
Millman, Rebecca E.
中科院分区：
文献类型：
--
作者：
Di Liberto, Giovanni M.;Lalor, Edmund C.;Millman, Rebecca E.
语言感知可能由一个层次化的大脑皮层系统来支撑，该系统试图将“外部”传入的感觉输入与“内部”自上而下的预测相匹配。先验知识调节对即将到来的刺激的内部预测，并在颞叶和额叶下部皮质发挥作用。在这里，我们使用源空间脑磁图(MEG)来研究语音处理网络中支持先验知识整合的时空动力学。先验知识被操纵以1)增加语音句子的感知可理解性，以及2)将语音可理解性变化的知觉效应与语音刺激的声学差异分离。大脑皮质对语音时间包膜的夹带作用受到先验知识的影响：这种影响在左下额回(IFG)较早出现(类似于50ms)，然后在Heschl‘s回(HG)出现(类似于100ms)，并持续到类似250ms的潜伏期。直接传递函数(DTF)用于估计感兴趣位置之间的直接Granger因果关系。与皮质夹带的结果一致，这一分析表明，先验知识增强了从左侧IFG到左侧所有感兴趣区的自上而下的联系，即HG、颞上沟(STS)和颞中回(MTG)。此外，可听得懂的语音增加了左STS和左HG之间的自上而下的信息流，并增加了高阶颞叶皮质的自下而上的信息流，特别是STS和MTG之间的信息流。这些结果与解释这种机制的理论是一致的，这种机制是上行和下行大脑皮层相互作用的结果，例如预测编码。总而言之，这项研究提供了一个关于先验知识如何、何时、何地影响连续言语感知的详细观点。
Speech perception may be underpinned by a hierarchical cortical system, which attempts to match "external" incoming sensory inputs with "internal" top-down predictions. Prior knowledge modulates internal predictions of an upcoming stimulus and exerts its effects in temporal and inferior frontal cortex. Here, we used source-space magnetoencephalography (MEG) to study the spatiotemporal dynamics underpinning the integration of prior knowledge in the speech processing network. Prior knowledge was manipulated to i) increase the perceived intelligibility of speech sentences, and ii) dissociate the perceptual effects of changes in speech intelligibility from acoustical differences in speech stimuli. Cortical entrainment to the speech temporal envelope, which accounts for neural activity specifically related to sensory information, was affected by prior knowledge: This effect emerged early (similar to 50 ms) in left inferior frontal gyrus (IFG) and then (similar to 100 ms) in Heschl's gyrus (HG), and was sustained until latencies of similar to 250 ms. Directed transfer function (DTF) measures were used for estimating direct Granger causal relations between locations of interest. In line with the cortical entrainment result, this analysis indicated that prior knowledge enhanced top-down connections from left IFG to all the left temporal areas of interest namely HG, superior temporal sulcus (STS), and middle temporal gyrus (MTG). In addition, intelligible speech increased top-down information flow between left STS and left HG, and increased bottom-up flow in higher-order temporal cortex, specifically between STS and MTG. These results are compatible with theories that explain this mechanism as a result of both ascending and descending cortical interactions, such as predictive coding. Altogether, this study provides a detailed view of how, where and when prior knowledge influences continuous speech perception.