Flevaris Anastasia V, Murray Scott O
Department of Psychology, University of Washington, Seattle, Washington 98195
Department of Psychology, University of Washington, Seattle, Washington 98195.
J Neurosci. 2015 Sep 2;35(35):12273-80. doi: 10.1523/JNEUROSCI.1409-15.2015.
Neural responses in primary visual cortex (V1) depend on stimulus context in seemingly complex ways. For example, responses to an oriented stimulus can be suppressed when it is flanked by iso-oriented versus orthogonally oriented stimuli but can also be enhanced when attention is directed to iso-oriented versus orthogonal flanking stimuli. Thus the exact same contextual stimulus arrangement can have completely opposite effects on neural responses-in some cases leading to orientation-tuned suppression and in other cases leading to orientation-tuned enhancement. Here we show that stimulus-based suppression and enhancement of fMRI responses in humans depends on small changes in the focus of attention and can be explained by a model that combines feature-based attention with response normalization.
Neurons in the primary visual cortex (V1) respond to stimuli within a restricted portion of the visual field, termed their "receptive field." However, neuronal responses can also be influenced by stimuli that surround a receptive field, although the nature of these contextual interactions and underlying neural mechanisms are debated. Here we show that the response in V1 to a stimulus in the same context can either be suppressed or enhanced depending on the focus of attention. We are able to explain the results using a simple computational model that combines two well established properties of visual cortical responses: response normalization and feature-based enhancement.
初级视觉皮层（V1）中的神经反应似乎以复杂的方式依赖于刺激背景。例如，当一个有方向的刺激被同向而非正交方向的刺激包围时，对该刺激的反应可能会受到抑制，但当注意力指向同向而非正交的侧翼刺激时，反应也可能增强。因此，完全相同的背景刺激排列对神经反应可能产生完全相反的影响——在某些情况下导致方向调谐抑制，而在其他情况下导致方向调谐增强。在这里，我们表明，人类功能性磁共振成像（fMRI）反应基于刺激的抑制和增强取决于注意力焦点的微小变化，并且可以用一个将基于特征的注意力与反应归一化相结合的模型来解释。
初级视觉皮层（V1）中的神经元对视野中一个受限部分内的刺激做出反应，这部分被称为它们的“感受野”。然而，神经元反应也会受到感受野周围刺激的影响，尽管这些背景相互作用的性质和潜在神经机制存在争议。在这里，我们表明，V1对相同背景下刺激的反应根据注意力焦点的不同，要么被抑制，要么被增强。我们能够使用一个简单的计算模型来解释这些结果，该模型结合了视觉皮层反应的两个已确立的特性：反应归一化和基于特征的增强。
