速度和距离对三维空间中时空整合的不同影响：行为与神经证据

Spatiotemporal integration is one of the most important cognitive functions, which is critical for the daily survival of human being. In order to catch behavioural targets or avoid dangerous/fatal collisions, the human brain needs to accurately integrate the spatial and the temporal information of moving objects. Although it has been suggested that left inferior parietal cortex and bilateral dorsal frontoparietal network are involved in the spatiotemopral integration process during time to collision (TTC) judgments, four important questions with regard to spatiotemporal integration remain unknown. In six fMRI experiments and six ERP experiments of the present project, we aim to answer the following four research questions: (1) The differential effects of distance and velocity on spatiotemporal integration during time to collision judgments. TTC is conjointly determined by distance and velocity (time=distance/velocity). It remains unknown, however, whether distance and velocity contribute differently to the spatiotemporal integration process. We thus aim to dissociate the potentially different effect of distance and velocity on TTC judgments. (2) The effect of spatial reference frame/personal perspective. All the previous studies in this field focused on the perceptual judgments on TTC of two external objects. In most situations of real life, however, we need to estimate the TTC of moving objects to ourselves and correspondingly plan actions. Therefore, we next aim to dissociate the differential neural correlates underlying spatiotemporal integration during purely perceptual judgments and during self-initiated actions. (3) Spatiotemporal integration along the depth dimension, in which we aim to extend the researches on spatiotemporal integration to three-dimensional space. (4) The effect of social properties/emotional valence of a moving object (e.g., rewarding vs. threatening) on spatiotemporal integration, and its potential interaction with the distance and the velocity dimensions of a moving object.

时空整合是人类赖以生存的一项重要认知功能:人脑需要将运动物体的空间信息和时间信息整合起来,才能准确判断客体之间或客体与自身的碰撞时间,从而调节运动系统以有效地拦截行为目标或回避危险/致命撞击。现有的时空整合机制研究共同忽略了四个重要方面:(1)速度和距离对时空整合的不同影响;(2)在纯知觉判断和自发动作 (self-initiated actions) 两种情境下,时空整合机制的异同;(3)在深度维度 (depth dimension) 上的时空整合机制;(4)客体的社会性(rewarding vs. threatening)对时空整合的影响及其与距离和速度的交互作用。在本项目的8个fMRI和8个ERP实验中,我将结合虚拟现实、fMRI、ERP和眼动追踪等技术,将时空整合拓展至三维空间、分离距离和速度对其的不同影响、并进一步探讨空间参考框架和移动客体的社会性对时空整合的影响。

时空整合是人类赖以生存的一项重要认知功能：人脑需要将运动物体的空间信息和时间信息整合起来，才能准确判断客体之间或客体与自身的碰撞时间，从而调节运动系统以有效地拦截行为目标或回避危险/致命撞击。在日常生活中，马路上高速行驶的车辆，即使它是从较远的地方驶来，仍然让人感到害怕，因此人们宁愿等待车辆驶过路口之后，再过马路；相反，面对从近处低速驶来的车辆，人们感觉更加从容，更倾向于在车辆驶过路口前提前穿过马路。由此我们假设，速度和距离对时空整合会有不同的影响。在本项目中，我们的一系列研究围绕以下两个问题展开：（1）速度和距离对碰撞任务中碰撞时间判断的不同影响；（2）深度维度（近远空间）对物体感知的影响。首先，我们的行为和神经数据一致表明，速度和距离在碰撞任务中对时间预测有不同的影响。在行为层面上，时间预测在速度增加条件下更容易被干扰。在神经层面上，碰撞时间（time to collision, TTC）网络的额顶部分不论在速度还是距离维度下，均参与时间预测。另外，我们发现了碰撞任务中速度特异性和距离特异性的网络。一方面，速度增加条件与早期视觉皮层神经活动的增加以及早期视觉皮层和TTC网络功能连接的增加有关；另一方面，距离变化条件与默认网络的神经活动有关。其次，在探讨深度维度对物体感知影响的系列实验中，我们的结果表明：（1）视觉主导效应会随着空间的深度维度而改变。尽管在近远空间中都能观察到显著的视觉主导效应，但是远空间的视觉主导效应显著强于近空间的视觉主导效应；（2）顶枕联合区在近远空间加工中扮演着交换背侧视觉通路和腹侧视觉通路信息的重要角色；（3）早期视觉皮层和高水平腹侧视觉通路以及前额叶皮层功能性联结的增强使得人类有能力保持对物体的稳定认知，从而产生大小恒常性。