Mitchell D E, Gingras G
Psychology Department Dalhousie University Halifax, Nova Scotia, B3H 4J1, Canada.
Curr Biol. 1998 Oct 22;8(21):1179-82. doi: 10.1016/s0960-9822(07)00489-7.
It is now well established that the anatomical and functional development of the central visual pathways of a number of higher mammalian species is activity-dependent [1-3]. This dependence was revealed by the functional effects of an early period of monocular deprivation, where one eye of a young animal was deprived for a time of patterned visual input. Subsequently, most cells in the visual cortex (area 17) could be excited only by visual stimuli delivered to the non deprived eye [4-6] and the animal appeared blind through the deprived eye [7,8]. These effects have been attributed to a competitive activity-dependent mechanism in development, whereby the two eyes compete for control of cortical cells [9,10]. There are, however, suggestions that the substantial recovery that can occur after monocular deprivation may be mediated by a different mechanism. Here, insight into the nature of this mechanism has been provided by monitoring the speed of changes in the vision of the deprived eye of a kitten after 6 days of monocular deprivation. Although both eyes were open during the recovery period, the kitten was able to see with its deprived eye only 2 hours after visual input was restored to this eye. The visual acuity of this eye improved rapidly in the first 24 hours and continued in an orderly way for 6 weeks. In contrast to the effects during monocular deprivation, which depend upon a competitive activity-dependent process, we propose that the events that follow deprivation rely on a mechanism driven by the absolute level of visually evoked activity through the formerly deprived eye.
现在已经充分证实，许多高等哺乳动物物种的中枢视觉通路的解剖学和功能发育依赖于活动[1-3]。这种依赖性是通过早期单眼剥夺的功能效应揭示的，在早期单眼剥夺中，幼年动物的一只眼睛在一段时间内被剥夺了有图案的视觉输入。随后，视觉皮层（17区）中的大多数细胞只能被传递到未被剥夺的眼睛的视觉刺激所兴奋[4-6]，并且动物通过被剥夺的眼睛看起来是失明的[7,8]。这些效应被归因于发育过程中一种依赖活动的竞争机制，即两只眼睛竞争对皮层细胞的控制[9,10]。然而，有迹象表明，单眼剥夺后可能发生的显著恢复可能是由一种不同的机制介导的。在这里，通过监测小猫单眼剥夺6天后被剥夺眼睛的视力变化速度，对这种机制的性质有了深入了解。尽管在恢复期间两只眼睛都是睁开的，但在视觉输入恢复到这只被剥夺的眼睛仅2小时后，小猫就能用这只眼睛看到东西了。这只眼睛的视力在最初的24小时内迅速提高，并以有序的方式持续了6周。与单眼剥夺期间依赖于竞争活动依赖过程的效应相反，我们提出，剥夺后发生的事件依赖于一种由通过先前被剥夺的眼睛的视觉诱发活动的绝对水平驱动的机制。
