Lamme V A, Zipser K, Spekreijse H
Graduate School of Neurosciences, Department of Medical Physics, Academic Medical Center, University of Amsterdam, and The Netherlands Ophthalmic Research Institute, P.O. Box 12141, 1100 AC Amsterdam, The Netherlands.
Proc Natl Acad Sci U S A. 1998 Mar 17;95(6):3263-8. doi: 10.1073/pnas.95.6.3263.
By means of their small receptive fields (RFs), neurons in primary visual cortex perform highly localized analyses of the visual scene, far removed from our normal unified experience of vision. Local image elements coded by the RF are put into more global context, however, by means of modulation of the responses of the V1 neurons. Contextual modulation has been shown to follow closely the perceptual interpretation of the scene as a whole. This would suggest that some aspects of contextual modulation can be recorded only in awake and perceiving animals. In this study, multi-unit activity was recorded with implanted electrodes from primary visual cortex of awake, fixating monkeys viewing textured displays in which figure and ground regions were segregated by differences in either orientation or motion. Contextual modulation was isolated from local RF processing, by keeping RF stimulation identical across trials while sampling responses for various positions of the RF relative to figure and ground. Contextual modulation was observed to unfold spatially and temporally in a way that closely resembles the figure-ground percept. When recording was repeated, but with the animals anesthetized, the figure-ground related modulatory activity was selectively suppressed. RF tuning properties, however, remained unaffected. The results show that the modulatory activity is functionally distinct from the RF properties. V1 thus hosts distinct regimes of activity that are mediated by separate mechanisms and that depend differentially on the animal being awake or anesthetized.
通过其小感受野（RFs），初级视觉皮层中的神经元对视觉场景进行高度局部化的分析，这与我们正常的统一视觉体验相去甚远。然而，通过对V1神经元反应的调制，由RF编码的局部图像元素被置于更全局的背景中。上下文调制已被证明与对整个场景的感知解释密切相关。这表明上下文调制的某些方面只能在清醒且有感知的动物中记录。在本研究中，用植入电极从清醒、注视的猴子的初级视觉皮层记录多单元活动，这些猴子观看纹理显示，其中图形和背景区域通过方向或运动的差异而分离。通过在试验中保持RF刺激相同，同时对RF相对于图形和背景的不同位置采样反应，将上下文调制与局部RF处理分离。观察到上下文调制在空间和时间上以与图形-背景感知非常相似的方式展开。当重复记录，但动物处于麻醉状态时，与图形-背景相关的调制活动被选择性抑制。然而，RF调谐特性保持不变。结果表明，调制活动在功能上与RF特性不同。因此，V1包含由不同机制介导的不同活动模式，并且不同程度地依赖于动物是清醒还是麻醉。
