Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, Ramat Gan 52900, Israel.
J Neurosci. 2010 Aug 18;30(33):11232-45. doi: 10.1523/JNEUROSCI.5177-09.2010.
Visual processing shows a highly distributed organization in which the presentation of a visual stimulus simultaneously activates neurons in multiple columns across several cortical areas. It has been suggested that precise spatiotemporal activity patterns within and across cortical areas play a key role in higher cognitive, motor, and visual functions. In the visual system, these patterns have been proposed to take part in binding stimulus features into a coherent object, i.e., to be involved in perceptual grouping. Using voltage-sensitive dye imaging (VSDI) in behaving monkeys (Macaca fascicularis, males), we simultaneously measured neural population activity in the primary visual cortex (V1) and extrastriate cortex (V2, V4) at high spatial and temporal resolution. We detected time point population events (PEs) in the VSDI signal of each pixel and found that they reflect transient increased neural activation within local populations by establishing their relation to spiking and local field potential activity. Then, we searched for repeating space and time relations between the detected PEs. We demonstrate the following: (1) spatiotemporal patterns occurring within (horizontal) and across (vertical) early visual areas repeat significantly above chance level; (2) information carried in only a few patterns can be used to reliably discriminate between stimulus categories on a single-trial level; (3) the spatiotemporal patterns yielding high classification performance are characterized by late temporal occurrence and top-down propagation, which are consistent with cortical mechanisms involving perceptual grouping. The pattern characteristics and the robust relation between the patterns and the stimulus categories suggest that spatiotemporal activity patterns play an important role in cortical mechanisms of higher visual processing.
视觉处理呈现出高度分布式的组织，其中视觉刺激的呈现会同时激活多个皮质区域中的多个柱神经元。有人认为，皮质区域内和跨区域的精确时空活动模式在高级认知、运动和视觉功能中起着关键作用。在视觉系统中，这些模式被认为参与将刺激特征绑定到一个连贯的物体中，即参与知觉分组。我们使用行为猕猴（Macaca fascicularis，雄性）中的电压敏感染料成像（VSDI），以高空间和时间分辨率同时测量初级视觉皮层（V1）和外纹状皮层（V2、V4）中的神经元群体活动。我们在每个像素的 VSDI 信号中检测到时间点群体事件（PE），并通过将其与尖峰和局部场电位活动建立关系，发现它们反映了局部群体中短暂增加的神经激活。然后，我们搜索检测到的 PE 之间重复的空间和时间关系。我们证明了以下几点：（1）在早期视觉区域内（水平）和跨区域（垂直）发生的时空模式显著高于随机水平；（2）仅通过少数几个模式传递的信息可用于在单次试验水平上可靠地区分刺激类别；（3）产生高分类性能的时空模式的特征是晚期时间发生和自上而下的传播，这与涉及知觉分组的皮质机制一致。模式特征以及模式与刺激类别的稳健关系表明，时空活动模式在高级视觉处理的皮质机制中起着重要作用。
