It is known that the extrastriate cortex is activated by visual symmetry. This activation generates an ERP component called the Sustained Posterior Negativity (SPN). SPN amplitude increases (i.e., becomes more negative) with repeated presentations. We exploited this SPN priming effect to test whether the extrastriate symmetry response is gated by element luminance polarity. On each trial, participants observed three stimuli (patterns of dots) in rapid succession (500 ms. with 200 ms. gaps). The patterns were either symmetrical or random. The dot elements were either black or white on a grey background. The triplet sequences either showed repeated luminance (black > black > black, or white > white > white) or changing luminance (black > white > black, or white > black > white). As predicted, SPN priming was comparable in repeated and changing luminance conditions. Therefore, symmetry with black elements is not processed independently from symmetry with white elements. Source waveform analysis confirmed that this priming happened within the extrastriate symmetry network. We conclude that the network pools information across luminance polarity channels.

中文翻译：

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电生理启动效应证实，超对称光网络不被亮度极性控制

已知通过视觉对称来激活外泌皮层。这种激活会生成一个称为后持续负性（SPN）的ERP组件。SPN振幅随着重复演示而增加（即变得更负）。我们利用了这种SPN启动效应测试元件的亮度极性是否控制了外对称的响应。在每个试验中，参与者观察到三个连续的刺激（点状图案）（500毫秒，间隔200毫秒）。模式是对称的或随机的。点元素在灰色背景上为黑色或白色。三联体序列显示重复的亮度（黑色>黑色>黑色，或白色>白色>白色）或变化的亮度（黑色>白色>黑色，或白色>黑色>白色）。如预测的那样，在重复和不断变化的亮度条件下，SPN启动可以媲美。因此，与黑色元素的对称性并非独立于与白色元素的对称性而被处理。信号源波形分析证实，这种引发是在极对称网络内发生的。