Department of Psychology, Stanford University, Jordan Hall, Building 420, 450 Serra Mall, Stanford, CA 94305, United States.
Université de Toulouse, Centre de Recherche Cerveau et Cognition, Toulouse, France; Centre National de la Recherche Scientifique, Toulouse Cedex, France.
Neuroimage. 2018 Feb 15;167:316-330. doi: 10.1016/j.neuroimage.2017.11.051. Epub 2017 Nov 23.
Neuroimaging studies have identified multiple extra-striate visual areas that are sensitive to symmetry in planar images (Kohler et al., 2016; Sasaki et al., 2005). Here, we investigated which of these areas are directly involved in perceptual decisions about symmetry, by recording high-density EEG in participants (n = 25) who made rapid judgments about whether an exemplar image contained rotation symmetry or not. Stimulus-locked sensor-level analysis revealed symmetry-specific activity that increased with increasing order of rotation symmetry. Response-locked analysis identified activity occurring between 600 and 200 ms before the button-press, that was directly related to perceptual decision making. We then used fMRI-informed EEG source imaging to characterize the dynamics of symmetry-specific activity within an extended network of areas in visual cortex. The most consistent cortical source of the stimulus-locked activity was VO1, a topographically organized area in ventral visual cortex, that was highly sensitive to symmetry in a previous study (Kohler et al., 2016). Importantly, VO1 activity also contained a strong decision-related component, suggesting that this area plays a crucial role in perceptual decisions about symmetry. Other candidate areas, such as lateral occipital cortex, had weak stimulus-locked symmetry responses and no evidence of correlation with response timing.
神经影像学研究已经确定了多个对平面图像的对称性敏感的额皮质外视觉区域（Kohler 等人，2016；Sasaki 等人，2005）。在这里，我们通过记录快速判断示例图像是否包含旋转对称性的参与者（n=25）的高密度 EEG，研究了这些区域中哪些区域直接参与了对称性的知觉决策。刺激锁定传感器级分析显示，对称性特异性活动随着旋转对称性的增加而增加。反应锁定分析确定了在按钮按下之前 600 到 200 毫秒之间发生的与知觉决策直接相关的活动。然后，我们使用 fMRI 启发的 EEG 源成像来描述视觉皮层中扩展的网络内对称性特异性活动的动态。刺激锁定活动的最一致的皮质源是 VO1，这是腹侧视觉皮层中一个具有地形组织的区域，在之前的研究中对对称性非常敏感（Kohler 等人，2016）。重要的是，VO1 活动还包含一个强烈的决策相关成分，这表明该区域在对称性的知觉决策中起着关键作用。其他候选区域，如外侧枕叶皮层，具有较弱的刺激锁定对称性反应，并且没有与响应时间相关的证据。
