Rekauzke Sascha, Nortmann Nora, Staadt Robert, Hock Howard S, Schöner Gregor, Jancke Dirk
Optical Imaging Group, Institut für Neuroinformatik, Ruhr University Bochum, 44801 Bochum, Germany.
Department of Psychology, Florida Atlantic University, Boca Raton, Florida 33486, and.
J Neurosci. 2016 Feb 10;36(6):1902-13. doi: 10.1523/JNEUROSCI.3235-15.2016.
Differences between visual pathways representing darks and lights have been shown to affect spatial resolution and detection timing. Both psychophysical and physiological studies suggest an underlying retinal origin with amplification in primary visual cortex (V1). Here we show that temporal asymmetries in the processing of darks and lights create motion in terms of propagating activity across V1. Exploiting the high spatiotemporal resolution of voltage-sensitive dye imaging, we captured population responses to abrupt local changes of luminance in cat V1. For stimulation we used two neighboring small squares presented on either bright or dark backgrounds. When a single square changed from dark to bright or vice versa, we found coherent population activity emerging at the respective retinal input locations. However, faster rising and decay times were obtained for the bright to dark than the dark to bright changes. When the two squares changed luminance simultaneously in opposite polarities, we detected a propagating wave front of activity that originated at the cortical location representing the darkened square and rapidly expanded toward the region representing the brightened location. Thus, simultaneous input led to sequential activation across cortical retinotopy. Importantly, this effect was independent of the squares' contrast with the background. We suggest imbalance in dark-bright processing as a driving force in the generation of wave-like activity. Such propagation may convey motion signals and influence perception of shape whenever abrupt shifts in visual objects or gaze cause counterchange of luminance at high-contrast borders.
An elementary process in vision is the detection of darks and lights through the retina via ON and OFF channels. Psychophysical and physiological studies suggest that differences between these channels affect spatial resolution and detection thresholds. Here we show that temporal asymmetries in the processing of darks and lights create motion signals across visual cortex. Using two neighboring squares, which simultaneously counterchanged luminance, we discovered propagating activity that was strictly drawn out from cortical regions representing the darkened location. Thus, a synchronous stimulus event translated into sequential wave-like brain activation. Such propagation may convey motion signals accessible in higher brain areas, whenever abrupt shifts in visual objects or gaze cause counterchange of luminance at high-contrast borders.
已表明代表暗与亮的视觉通路差异会影响空间分辨率和检测时机。心理物理学和生理学研究均表明其根源在于视网膜，并在初级视皮层（V1）中得到放大。在此我们表明，暗与亮处理过程中的时间不对称会在V1中通过传播活动产生运动。利用电压敏感染料成像的高时空分辨率，我们记录了猫V1中对亮度突然局部变化的群体反应。为进行刺激，我们使用了在亮背景或暗背景上呈现的两个相邻小方块。当单个方块从暗变亮或反之亦然时，我们在各自的视网膜输入位置发现了连贯的群体活动。然而，亮到暗变化的上升和衰减时间比暗到亮变化更快。当两个方块同时以相反极性改变亮度时，我们检测到一个活动的传播波前，它起源于代表变暗方块的皮层位置，并迅速向代表变亮位置的区域扩展。因此，同时输入导致了跨皮层视网膜拓扑图的顺序激活。重要的是，这种效应与方块与背景的对比度无关。我们认为暗 - 亮处理的不平衡是产生波状活动的驱动力。每当视觉对象或注视的突然变化导致高对比度边界处亮度的反向变化时，这种传播可能会传递运动信号并影响形状感知。
视觉中的一个基本过程是通过视网膜的ON和OFF通道检测暗与亮。心理物理学和生理学研究表明，这些通道之间的差异会影响空间分辨率和检测阈值。在此我们表明，暗与亮处理过程中的时间不对称会在视觉皮层中产生运动信号。通过使用两个相邻的方块，它们同时反向改变亮度，我们发现了从代表变暗位置的皮层区域严格引出的传播活动。因此，一个同步刺激事件转化为顺序的波状脑激活。每当视觉对象或注视的突然变化导致高对比度边界处亮度的反向变化时，这种传播可能会传递在更高脑区可获取的运动信号。
