靶刺激出现前感觉系统内神经活动的变化对感觉通道主导方向的因果效应

Although constantly bombarded with streams of information from multiple sensory modalities, the human brain does not give equal weights to information from different modalities, which results in that information from a particular sensory modality is preferentially selected under certain circumstance and eventually dominates behavior and awareness. This phenomenon is termed as the sensory dominance effect. Previous research from our lab revealed that the visual and auditory system showed different patterns of functional connectivity with the frontoparietal network and the default mode network, depending on the direction of sensory dominance (visual vs. auditory dominance) (e.g., Huang et al., Journal of Neuroscience, 2015). What remains a critical and open question is the causal relation, i.e. whether the direction of sensory dominance (visual vs. auditory dominance) is causally determined by variance of neural activity in the primary/secondary sensory system during early phase of cognitive processing. By adopting fMRI, EEG, and behavioral oscillation (dense sampling) techniques in the six experiments of the present project, we either increased the pre-stimulus neural activity in the primary/secondary sensory system via the top-down attentional pre-cue paradigm, or decreased the pre-stimulus neural activity in the primary/secondary sensory system via the adaptation paradigm. By varying the pre-stimulus neural activity in the primary/secondary system, we aimed at investigating the brain substrates, neural and behavioral oscillations underlying the causal relation between pre-stimulus variation of neural activity in the sensory system and the direction of sensory dominance.

人脑时刻面临同时来自多个感觉通道的海量信息，但人脑并不给予每个感觉通道相等的权重，这导致某个感觉通道信息得到优先加工，并最终主导意识和行为。这种现象被称为感觉通道主导效应。我们实验室的一系列研究表明，感觉通道主导效应的方向与初级/次级感觉系统和额顶网络、默认网络之间的功能联结模式紧密相关（e.g. Huang et al., Journal of Neuroscience, 2015）。下一步亟待回答的是因果关系问题：感觉通道主导的方向是否由感觉系统中神经活动的早期变化导致。在本项目的六个fMRI、EEG和行为节律实验中，我们将使用适应（adaptation）、自上而下注意提示（pr-ecue）和跨通道相位重设（cross-modal phase reset）范式，来考察多感觉靶刺激出现之前，感觉系统内的神经活动变化与感觉通道主导效应方向之间因果关系的脑结构、神经和行为节律机制。

人类生活在一个多感觉信息的现实世界中，由于认知资源有限，大脑并不会给予所有信息相同的加工权重，这就导致某个感觉通道信息得到优先加工，并最终主导意识和行为，这种现象就被称为感觉通道主导 (sensory dominance) 效应。以往研究发现感觉通道主导效应本身的神经机制，以及视听双通道靶刺激出现前脑内自发神经活动的波动对感觉通道主导效应方向的影响。进一步地，我们将考察多通道靶刺激出现前，感觉系统内部神经活动的变化对感觉通道主导方向的因果影响。将 Colavita 范式与自上而下（top-down）的注意提示范式相结合，利用内源性线索对感觉皮层的神经活动的调节，进一步探讨视觉、听觉皮层神经活动的提前活动是如何调控跨通道选择性注意对视听觉信息选择的优先性。结果表明：（1）不论提示注意通道的线索以何种方式呈现，线索引导的注意均能够调节感觉主导效应的方向。在注意视觉时，视觉优先比例较听觉优先更高；在注意听觉时，两者没有显著差异。（2）注意能够调节感觉主导效应的大小。当线索指向视觉通道时，视觉主导效应值比听觉主导效应值更大；当线索指向听觉通道时，两者的感觉主导效应值大小没有显著差异。（3）在注意视觉通道时，视觉皮层神经活动升高使得视觉信息更快得到加工，引起视觉优先反应的比例提升；当听觉皮层与运动皮层的连通性增强，则会做出听觉优先的反应。在注意听觉通道时，听觉皮层神经活动升高使得听觉信息更快得到加工，引起听觉优先比例提升，且此时运动皮层的神经活动越强，听觉主导效应量就越大。