Gallant J L, Connor C E, Van Essen D C
Department of Anatomy and Neurobiology, Washington University Medical School, St. Louis, MO 63110, USA.
Neuroreport. 1998 May 11;9(7):1673-8. doi: 10.1097/00001756-199805110-00075.
Under natural viewing conditions primates make frequent exploratory eye movements across complex scenes. We recorded neural activity of 62 cells in visual areas V1, V2 and V4 in an awake behaving monkey that freely viewed natural images. About half of the cells studied showed a modulation in firing rate following some of the eye movements made during free viewing, though the proportions showing a discernible modulation varied across areas. These cells were also examined under controlled viewing conditions in which gratings or natural image patches were flashed in and around the classical receptive field while the animal performed a fixation task. Activity rates were generally highest with flashed gratings and lowest during free viewing. Flashed natural image patches evoked responses between these two extremes, and the responses were higher when the patches were confined to the classical receptive field than when they extended into the non-classical surround. Thus the reduction of activity during free viewing relative to that obtained with flashed gratings is partly attributable to natural images being less effective stimuli and partly to suppressive spatio-temporal neural mechanisms that are important during natural vision.
在自然观看条件下，灵长类动物会频繁地在复杂场景中进行探索性眼动。我们记录了一只清醒行为猴子在自由观看自然图像时，视觉区域V1、V2和V4中62个细胞的神经活动。在自由观看过程中，约一半被研究的细胞在某些眼动之后表现出放电率的调制，尽管表现出可察觉调制的比例在不同区域有所不同。在受控观看条件下，我们也对这些细胞进行了检测，即当动物执行注视任务时，在经典感受野及其周围闪现光栅或自然图像块。通常，闪现光栅时的活动率最高，自由观看时最低。闪现的自然图像块在这两个极端之间诱发反应，当图像块局限于经典感受野时的反应高于其扩展到非经典周边区域时的反应。因此，相对于闪现光栅时获得的活动，自由观看期间活动的减少部分归因于自然图像作为刺激的效果较差，部分归因于在自然视觉中起重要作用的抑制性时空神经机制。
