Department of Biomedical Engineering, City College of New York, New York, NY, USA.
U.S. Army Research Laboratory, Aberdeen Proving Ground, MD, USA.
J Vis. 2021 Sep 1;21(10):7. doi: 10.1167/jov.21.10.7.
Relatively little is known about visual processing during free-viewing visual search in realistic dynamic environments. Free-viewing is characterized by frequent saccades. During saccades, visual processing is thought to be suppressed, yet we know that the presaccadic visual content can modulate postsaccadic processing. To better understand these processes in a realistic setting, we study here saccades and neural responses elicited by the appearance of visual targets in a realistic virtual environment. While subjects were being driven through a 3D virtual town, they were asked to discriminate between targets that appear on the road. Using a system identification approach, we separated overlapping and correlated activity evoked by visual targets, saccades, and button presses. We found that the presence of a target enhances early occipital as well as late frontocentral saccade-related responses. The earlier potential, shortly after 125 ms post-saccade onset, was enhanced for targets that appeared in the peripheral vision as compared to the central vision, suggesting that fast peripheral processing initiated before saccade onset. The later potential, at 195 ms post-saccade onset, was strongly modulated by the visibility of the target. Together these results suggest that, during natural viewing, neural processing of the presaccadic visual stimulus continues throughout the saccade, apparently unencumbered by saccadic suppression.
在现实动态环境中自由观看视觉搜索期间，人们对视觉处理的了解相对较少。自由观看的特点是频繁的眼跳。在眼跳期间，人们认为视觉处理被抑制，但我们知道，预眼跳视觉内容可以调节眼跳后的处理。为了在现实环境中更好地理解这些过程，我们在这里研究了在现实虚拟环境中出现视觉目标时的眼跳和神经反应。当受试者在 3D 虚拟城镇中被驱动时，他们被要求区分出出现在道路上的目标。我们使用系统识别方法，将由视觉目标、眼跳和按钮按下引起的重叠和相关活动分开。我们发现，目标的存在增强了早期枕叶以及晚期额中央与眼跳相关的反应。在眼跳开始后 125 毫秒左右出现的早期电位，对于出现在外围视觉中的目标比出现在中央视觉中的目标增强，这表明在眼跳开始之前，快速的外围处理就已经启动。在眼跳开始后 195 毫秒出现的后期电位，强烈地受到目标可见性的调制。这些结果表明，在自然观看期间，预眼跳视觉刺激的神经处理在整个眼跳过程中持续进行，显然不受眼跳抑制的影响。
