Dering Benjamin, Wright Damien, Gheorghiu Elena
Department of Psychology, University of Stirling, Stirling, FK9 4LA, Scotland, United Kingdom.
Patrick Wild Centre, Division of Psychiatry, Royal Edinburgh Hospital, Edinburgh, EH8 9XDScotland, United Kingdom.
Vis Neurosci. 2024 Dec 16;41:E005. doi: 10.1017/S0952523824000075.
Symmetry is a salient visual feature in the natural world, yet the perception of symmetry may be influenced by how natural lighting conditions (e.g., shading) fall on the object relative to its symmetry axis. Here, we investigate how symmetry detection may interact with luminance polarity grouping, and whether this modulates neural responses to symmetry, as evidenced by the Sustained Posterior Negativity (SPN) component of Event-Related Potentials (ERPs). Stimuli were dot patterns arranged either symmetrically (reflection, rotation, translation) or quasi-randomly, and by luminance polarity about a grouping axis (i.e., black dots on one side and white dots on the other). We varied the relative angular separation between the symmetry and polarity-grouping axes: 0, 30, 60, 90 deg. Participants performed a two interval-forced-choice (2IFC) task indicating which interval contained the symmetrical pattern. We found that accuracy for the 0 deg polarity-grouped condition was higher compared to the single-polarity condition for rotation and translation (but not reflection symmetry), and higher than all other angular difference (30, 60, 90) conditions for all symmetry types. The SPN was found to be separated topographically into an early and late component, with the early SPN being sensitive to luminance polarity grouping at parietal-occipital electrodes, and the late SPN sensitive to symmetry over central electrodes. The increase in relative angular differences between luminance polarity and symmetry axes highlighted changes between cardinal (0, 90 deg) and other (30, 60 deg) angles. Critically, we found a polarity-grouping effect in the SPN time window for noise only patterns, which was related to symmetry type, suggesting a task/ symmetry pattern influence on SPN processes. We conclude that luminance polarity grouping can facilitate symmetry perception when symmetry is not readily salient, as evidenced by polarity sensitivity of early SPN, yet it can also inhibit neural and behavioral responses when luminance polarity and symmetry axes are not aligned.
对称性是自然界中一个显著的视觉特征，然而，对称性的感知可能会受到自然光照条件（如阴影）相对于物体对称轴的照射方式的影响。在这里，我们研究对称性检测如何与亮度极性分组相互作用，以及这是否会调节对对称性的神经反应，事件相关电位（ERP）的持续后负波（SPN）成分证明了这一点。刺激物是点状图案，它们要么对称排列（反射、旋转、平移），要么近似随机排列，并根据围绕一个分组轴的亮度极性排列（即一侧为黑点，另一侧为白点）。我们改变了对称轴和极性分组轴之间的相对角间距：0、30、60、90度。参与者执行了一个二间隔强制选择（2IFC）任务，指出哪个间隔包含对称图案。我们发现，对于旋转和平移（但不是反射对称），0度极性分组条件下的准确率高于单极性条件，并且对于所有对称类型，该条件下的准确率高于所有其他角差（30、60、90）条件。发现SPN在地形上分为早期和晚期成分，早期SPN在顶枕电极对亮度极性分组敏感，晚期SPN在中央电极对对称性敏感。亮度极性轴和对称轴之间相对角差的增加突出了主角度（0,90度）和其他角度（30,60度）之间的变化。至关重要的是，我们在仅噪声图案的SPN时间窗口中发现了极性分组效应，这与对称类型有关，表明任务/对称图案对SPN过程有影响。我们得出结论，当对称性不明显时，亮度极性分组可以促进对称性感知，早期SPN的极性敏感性证明了这一点，但当亮度极性轴和对称轴不对齐时，它也会抑制神经和行为反应。
