Zarella Mark D, Ts'o Daniel Y
Department of Neurosurgery, SUNY Upstate Medical University, Syracuse, NY, USA.
Eye Brain. 2016 Oct 21;8:177-193. doi: 10.2147/EB.S105616. eCollection 2016.
Neurons in early visual cortical areas encode the local properties of a stimulus in a number of different feature dimensions such as color, orientation, and motion. It has been shown, however, that stimuli presented well beyond the confines of the classical receptive field can augment these responses in a way that emphasizes these local attributes within the greater context of the visual scene. This mechanism imparts global information to cells that are otherwise considered local feature detectors and can potentially serve as an important foundation for surface segmentation, texture representation, and figure-ground segregation. The role of early visual cortex toward these functions remains somewhat of an enigma, as it is unclear how surface segmentation cues are integrated from multiple feature dimensions. We examined the impact of orientation- and motion-defined surface segmentation cues in V1 and V2 neurons using a stimulus in which the two features are completely separable. We find that, although some cells are modulated in a cue-invariant manner, many cells are influenced by only one cue or the other. Furthermore, cells that are modulated by both cues tend to be more strongly affected when both cues are presented together than when presented individually. These results demonstrate two mechanisms by which cue combinations can enhance salience. We find that feature-specific populations are more frequently encountered in V1, while cue additivity is more prominent in V2. These results highlight how two strongly interconnected areas at different stages in the cortical hierarchy can potentially contribute to scene segmentation.
早期视觉皮层区域的神经元在多个不同特征维度（如颜色、方向和运动）中编码刺激的局部属性。然而，已经表明，呈现于经典感受野范围之外的刺激能够以一种在更大视觉场景背景下强调这些局部属性的方式增强这些反应。这种机制将全局信息赋予那些原本被视为局部特征检测器的细胞，并可能为表面分割、纹理表征和图形-背景分离奠定重要基础。早期视觉皮层对这些功能的作用仍有些神秘，因为尚不清楚表面分割线索是如何从多个特征维度整合而来的。我们使用一种两个特征完全可分离的刺激，研究了V1和V2神经元中由方向和运动定义的表面分割线索的影响。我们发现，虽然一些细胞以线索不变的方式被调制，但许多细胞仅受一种线索或另一种线索的影响。此外，受两种线索调制的细胞在两种线索同时呈现时往往比单独呈现时受到更强的影响。这些结果证明了线索组合增强显著性的两种机制。我们发现特定特征的细胞群在V1中更常见，而线索相加性在V2中更突出。这些结果突出了皮层层次结构中不同阶段的两个紧密相连的区域如何可能对场景分割做出贡献。
