Form-Cue Invariant Second-Order Neuronal Responses to Contrast Modulation in Primate Area V2
Form-Cue Invariant Second-Order Neuronal Responses to Contrast Modulation in Primate Area V2
复制标题
灵长类动物 V2 区对对比度调制的形式提示不变二阶神经元反应
DOI：
10.1523/jneurosci.0211-14.2014
复制
发表时间：
2014-09-03
影响因子：
5.3
通讯作者：
Baker, Curtis L., Jr.
中科院分区：
文献类型：
--
作者：
Li, Guangxing;Yao, Zhimo;Baker, Curtis L., Jr.
视觉系统的一个基本任务是提取物体图像之间的图-地边界，在自然场景中，这不仅是由亮度差异定义的，而且是由“二阶”对比度或纹理差异定义的。人类心理物理学对对比调制（CM）和其他二阶刺激的反应进行了广泛的研究，但对非人类灵长类动物二阶反应的神经元基质仍知之甚少。在这项研究中，我们使用CM模式和传统的亮度调制（LM）光栅记录了猕猴V2区域的单个神经元。CM刺激由固定的正弦波光栅载波模式构成，并由较低空间频率的漂移包络光栅调制。我们发现大约三分之一的视觉反应的V2神经元对CM刺激有明显的选择性载波空间频率，通常是方向，这显然是在神经元的LM光栅通带之外。这些神经元是“形式线索不变性”的，因为它们对CM包络空间频率和方向的调整与LM光栅非常相似。神经元被调谐到载波空间频率，通常比其最佳包络空间频率高2-4个八度，与人类心理物理学的结果相似。这些结果不同于由环绕抑制引起的CM响应，但可以根据滤波器-整流滤波器模型来理解。这样的神经元可以提供功能上有用的和明确的分割边界表示，以及人类感知二阶边界的似是而非的神经基质。
A fundamental task of the visual system is to extract figure-ground boundaries between images of objects, which in natural scenes are often defined not only by luminance differences but also by "second-order" contrast or texture differences. Responses to contrast modulation (CM) and other second-order stimuli have been extensively studied in human psychophysics, but the neuronal substrates of second-order responses in nonhuman primates remain poorly understood. In this study, we have recorded single neurons in area V2 of macaque monkeys, using both CM patterns as well as conventional luminance modulation (LM) gratings. CM stimuli were constructed from stationary sine wave grating carrier patterns, which were modulated by drifting envelope gratings of a lower spatial frequency. We found approximately one-third of visually responsive V2 neurons responded to CM stimuli with a pronounced selectivity to carrier spatial frequencies, and often orientations, that were clearly outside the neurons' passbands for LM gratings. These neurons were "form-cue invariant" in that their tuning to CM envelope spatial frequency and orientation was very similar to that for LM gratings. Neurons were tuned to carrier spatial frequencies that were typically 2-4 octaves higher than their optimal envelope spatial frequencies, similar to results from human psychophysics. These results are distinct from CM responses arising from surround suppression, but could be understood in terms of a filter-rectify-filter model. Such neurons could provide a functionally useful and explicit representation of segmentation boundaries as well as a plausible neural substrate for human perception of second-order boundaries.