Qiu Cheng, Burton Philip C, Kersten Daniel, Olman Cheryl A
J Vis. 2016 Jun 1;16(8):19. doi: 10.1167/16.8.19.
It has been shown that early visual areas are involved in contour processing. However, it is not clear how local and global context interact to influence responses in those areas, nor has the interarea coordination that yields coherent structural percepts been fully studied, especially in human observers. In this study, we used functional magnetic resonance imaging (fMRI) to measure activity in early visual cortex while observers performed a contour detection task in which alignment of Gabor elements and background clutter were manipulated. Six regions of interest (two regions, containing either the cortex representing the target or the background clutter, in each of areas V1, V2, and V3) were predefined using separate target versus background functional localizer scans. The first analysis using a general linear model showed that in the presence of background clutter, responses in V1 and V2 target regions of interest were significantly stronger to aligned than unaligned contours, whereas when background clutter was absent, no significant difference was observed. The second analysis using interarea correlations showed that with background clutter, there was an increase in V1-V2 coordination within the target regions when perceiving aligned versus unaligned contours; without clutter, however, correlations between V1 and V2 were similar no matter whether aligned contours were present or not. Both the average response magnitude and the connectivity analysis suggest different mechanisms support contour processing with or without background distractors. Coordination between V1 and V2 may play a major role in coherent structure perception, especially with complex scene organization.
研究表明，早期视觉区域参与轮廓处理。然而，尚不清楚局部和全局背景如何相互作用以影响这些区域的反应，而且产生连贯结构感知的区域间协调也尚未得到充分研究，尤其是在人类观察者中。在本研究中，我们使用功能磁共振成像（fMRI）来测量早期视觉皮层的活动，同时观察者执行一项轮廓检测任务，其中对Gabor元素的对齐和背景杂波进行了操控。使用单独的目标与背景功能定位扫描预先定义了六个感兴趣区域（在V1、V2和V3区域中各有两个区域，分别包含代表目标或背景杂波的皮层）。使用一般线性模型的首次分析表明，在存在背景杂波的情况下，V1和V2目标感兴趣区域对对齐轮廓的反应比对未对齐轮廓的反应明显更强，而当不存在背景杂波时，未观察到显著差异。使用区域间相关性的第二次分析表明，在存在背景杂波的情况下，在感知对齐轮廓与未对齐轮廓时，目标区域内V1-V2的协调性增加；然而，在没有杂波的情况下，无论是否存在对齐轮廓，V1和V2之间的相关性相似。平均反应幅度和连通性分析均表明，不同的机制支持有或没有背景干扰物时的轮廓处理。V1和V2之间的协调可能在连贯结构感知中起主要作用，尤其是在复杂场景组织中。
