Department of Vision & Cognition, Netherlands Institute for Neuroscience, Meibergdreef 47, 1105 BA Amsterdam, the Netherlands.
Department of Vision & Cognition, Netherlands Institute for Neuroscience, Meibergdreef 47, 1105 BA Amsterdam, the Netherlands; Department of Neuroscience, Zuckerman Mind Brain Behavior Institute, Columbia University, New York, NY 10032, USA.
Curr Biol. 2019 Mar 18;29(6):1019-1029.e4. doi: 10.1016/j.cub.2019.02.016. Epub 2019 Mar 7.
During visual perception, the brain enhances the representations of image regions that belong to figures and suppresses those that belong to the background. Natural images contain many regions that initially appear to be part of a figure when analyzed locally (proto-objects) but are actually part of the background if the whole image is considered. These proto-grounds must be correctly assigned to the background to allow correct shape identification and guide behavior. To understand how the brain resolves this conflict between local and global processing, we recorded neuronal activity from the primary visual cortex (V1) of macaque monkeys while they discriminated between n/u shapes that have a central proto-ground region. We studied the fine-grained spatiotemporal profile of neural activity evoked by the n/u shape and found that neural representation of the object proceeded from a coarse-to-fine resolution. Approximately 100 ms after the stimulus onset, the representation of the proto-ground region was enhanced together with the rest of the n/u surface, but after ∼115 ms, the proto-ground was suppressed back to the level of the background. Suppression of the proto-ground was only present in animals that had been trained to perform the shape-discrimination task, and it predicted the choice of the animal on a trial-by-trial basis. Attention enhanced figure-ground modulation, but it had no effect on the strength of proto-ground suppression. The results indicate that the accuracy of scene segmentation is sharpened by a suppressive process that resolves local ambiguities by assigning proto-grounds to the background.
在视觉感知过程中，大脑会增强属于图像主体的区域的表示，同时抑制属于背景的区域的表示。自然图像包含许多区域，这些区域在局部分析时（原对象）最初似乎是图像的一部分，但如果考虑整个图像，则实际上是背景的一部分。这些原背景必须正确地分配给背景，以允许正确的形状识别和指导行为。为了了解大脑如何解决局部和全局处理之间的这种冲突，我们在猕猴的初级视觉皮层（V1）记录神经元活动，同时它们对具有中心原背景区域的 n/u 形状进行区分。我们研究了 n/u 形状诱发的神经活动的精细时空分布，并发现物体的神经表示从粗到细分辨率进行。大约在刺激开始后 100 毫秒，原背景区域的表示与 n/u 表面的其余部分一起增强，但在大约 115 毫秒后，原背景被抑制回背景水平。原背景的抑制仅存在于接受过执行形状辨别任务训练的动物中，并且它基于每个试验的基础预测动物的选择。注意力增强了图形背景调制，但对原背景抑制的强度没有影响。结果表明，通过将原背景分配给背景来解决局部歧义的抑制过程可以提高场景分割的准确性。
