State Key Laboratory of Brain and Cognitive Science, Institute of Biophysics, Chinese Academy of Sciences, Beijing, China.
Brain Res Bull. 2011 Aug 10;86(1-2):97-105. doi: 10.1016/j.brainresbull.2011.06.004. Epub 2011 Jul 1.
Contrast-defined contours are one type of second-order contours, across which there are no differences in luminance. Although they can be always perceived, their responses have been only investigated when the spatial frequency of carrier, the background texture whose contrast is modulated to form contours, is much higher than that of contrast-defined contours, due to the interference of responses to luminance contours in other cases. In the present study, we examined visual responses in cat area 18 to the contrast-defined contours with carrier at same spatial frequency equal to neuron's preferred value for luminance contours, by establishing a control stimulus including all the luminance components but lack of the contrast contour information. Using single unit recording and intrinsic optical imaging, we demonstrated that contrast gratings with equally spatial-scaled carrier induced responses in a proportion of cat area 18 neurons with the preferred orientation similar to that for luminance contours, and the responses generated orientation maps similar to those for luminance contours. Our finding suggests that early visual cortex can process second-order contours regardless of the spatial frequency of carriers, in a way similar to the processing of luminance contours. This uniform manner of early visual processing might underlie the visual detection of both luminance contours and non-luminance second-order contours.
对比定义的轮廓是二阶轮廓的一种，在这些轮廓上亮度没有差异。尽管它们总是可以被感知，但由于在其他情况下对亮度轮廓的响应干扰，只有当载波的空间频率（其对比度调制以形成轮廓的背景纹理）远高于对比度定义的轮廓时，才会研究它们的响应。在本研究中，我们通过建立一个包括所有亮度成分但缺乏对比度轮廓信息的控制刺激，检查了猫 18 区对具有与神经元对亮度轮廓的最佳值相同空间频率的载波的对比度定义轮廓的视觉响应。使用单细胞记录和固有光学成像，我们证明了具有相同空间尺度载波的对比度光栅会在一定比例的猫 18 区神经元中引起类似于亮度轮廓的响应，并且产生的响应生成类似于亮度轮廓的方向图。我们的发现表明，早期视觉皮层可以处理二阶轮廓，而不管载波的空间频率如何，其处理方式类似于对亮度轮廓的处理。这种早期视觉处理的统一方式可能是亮度轮廓和非亮度二阶轮廓的视觉检测的基础。
