Rossi A F, Desimone R, Ungerleider L G
Laboratory of Brain and Cognition, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland 20892, USA.
J Neurosci. 2001 Mar 1;21(5):1698-709. doi: 10.1523/JNEUROSCI.21-05-01698.2001.
Recent studies have suggested that V1 neurons extract figures from their backgrounds, in that they respond better to interior features of figures than to equivalent features of background stimuli. This is reportedly true even when the figure boundaries are distant from the borders of the classical receptive field (RF). To test the role of V1 neurons in figure-ground segregation, we recorded their responses to texture figures on texture backgrounds, centered on the RF. The texture elements of the figures remained identical across trials, and figure boundaries were defined by orientation differences between the elements in the background texture relative to elements in the figure. For nearly all neurons (98/102), responses to a large texture figure did not differ from the responses to a uniform-texture background. Although many neurons gave enhanced responses to texture boundaries, this occurred only when the boundaries were within or close to the RF borders. Similar effects were found in V2. For neurons in V1, the limited spatial extent of the contextual modulation was not increased either at low stimulus contrast or when the animal was rewarded for detecting an orientation-defined figure. Thus, V1 neurons appear to signal texture boundaries rather than figures per se. Unexpectedly, many V1 neurons gave significant long-latency responses to texture stimuli located entirely outside the classical RF, up to 5 degrees from the RF border in some cases. However, these responses did not depend on the stimulus forming a figure that contained the RF. Although V1 neurons are influenced by stimuli outside the classical RF, they do not appear to segregate figures from ground.
最近的研究表明，V1神经元能从背景中提取图形，因为它们对图形的内部特征反应比对背景刺激的等效特征反应更好。据报道，即使图形边界与经典感受野（RF）的边界相距甚远，情况也是如此。为了测试V1神经元在图形-背景分离中的作用，我们记录了它们对以RF为中心的纹理背景上的纹理图形的反应。图形的纹理元素在各次试验中保持不变，图形边界由背景纹理中的元素与图形中的元素之间的方向差异定义。对于几乎所有的神经元（102个中的98个），对大纹理图形的反应与对均匀纹理背景的反应没有差异。尽管许多神经元对纹理边界有增强反应，但这仅在边界位于或靠近RF边界时才会发生。在V2中也发现了类似的效应。对于V1中的神经元，在低刺激对比度下或当动物因检测到方向定义的图形而得到奖励时，上下文调制的有限空间范围也没有增加。因此，V1神经元似乎是在标记纹理边界而不是图形本身。出乎意料的是，许多V1神经元对完全位于经典RF之外的纹理刺激给出了显著的长潜伏期反应，在某些情况下距离RF边界可达5度。然而，这些反应并不取决于刺激形成一个包含RF的图形。尽管V1神经元受到经典RF之外的刺激的影响，但它们似乎并没有将图形与背景分离。
