Zurawel Guy, Ayzenshtat Inbal, Zweig Shay, Shapley Robert, Slovin Hamutal
The Gonda Multidisciplinary Brain Research Center, Bar-Ilan University, 52900 Ramat Gan, Israel and.
Center for Neural Science, New York University, New York, New York 10003.
J Neurosci. 2014 Oct 22;34(43):14388-402. doi: 10.1523/JNEUROSCI.0848-14.2014.
We investigated the cortical mechanisms underlying the visual perception of luminance-defined surfaces and the preference for black over white stimuli in the macaque primary visual cortex, V1. We measured V1 population responses with voltage-sensitive dye imaging in fixating monkeys that were presented with white or black squares of equal contrast around a mid-gray. Regions corresponding to the squares' edges exhibited higher activity than those corresponding to the center. Responses to black were higher than to white, surprisingly to a much greater extent in the representation of the square's center. Additionally, the square-evoked activation patterns exhibited spatial modulations along the edges and corners. A model comprised of neural mechanisms that compute local contrast, local luminance temporal modulations in the black and white directions, and cortical center-surround interactions, could explain the observed population activity patterns in detail. The model captured the weaker contribution of V1 neurons that respond to positive (white) and negative (black) luminance surfaces, and the stronger contribution of V1 neurons that respond to edge contrast. Also, the model demonstrated how the response preference for black could be explained in terms of stronger surface-related activation to negative luminance modulation. The spatial modulations along the edges were accounted for by surround suppression. Overall the results reveal the relative strength of edge contrast and surface signals in the V1 response to visual objects.
我们研究了猕猴初级视觉皮层V1中亮度定义表面的视觉感知以及对黑色刺激优于白色刺激的偏好背后的皮层机制。我们在注视的猴子中使用电压敏感染料成像测量V1群体反应，这些猴子被呈现围绕中灰色的具有相等对比度的白色或黑色正方形。与正方形边缘对应的区域比与中心对应的区域表现出更高的活动。对黑色的反应高于对白色的反应，令人惊讶的是，在正方形中心的表征中这种差异程度要大得多。此外，正方形诱发的激活模式沿边缘和角落表现出空间调制。一个由计算局部对比度、黑白方向的局部亮度时间调制以及皮层中心-外周相互作用的神经机制组成的模型，可以详细解释观察到的群体活动模式。该模型捕捉到了对正（白色）和负（黑色）亮度表面做出反应的V1神经元的较弱贡献，以及对边缘对比度做出反应的V1神经元的较强贡献。此外，该模型展示了如何根据对负亮度调制更强的表面相关激活来解释对黑色的反应偏好。沿边缘的空间调制是由外周抑制引起的。总体而言，结果揭示了V1对视觉对象反应中边缘对比度和表面信号的相对强度。
