Freeman R D, Ohzawa I
Group in Neurobiology, University of California, Berkeley 94720.
J Neurosci. 1988 Jul;8(7):2491-506. doi: 10.1523/JNEUROSCI.08-07-02491.1988.
Animals that are deprived of vision in one eye during a vulnerable phase of development lose visual function of the eye. Although this phenomenon has been studied extensively, little is known about the mechanism of disconnection of the deprived eye from visual cortex. One fundamental question is whether input remains from that eye. We have examined the hypothesis that there is functional input from a deprived eye to visual cortex that cannot be observed with standard alternate tests of each eye. We have employed a robust visual stimulation procedure in which large sinusoidal gratings are presented to each eye, as well as to both eyes together, at varying relative phases or retinal disparities. Monocular and binocular stimulation was used to test kittens unilaterally deprived for brief, intermediate, or long periods. A fourth group of kittens was studied as normal controls. Standard methods were used to record from single cells in the striate cortex. After initial qualitative exploration of receptive fields, all testing and analysis were quantitative. As expected, monocular tests revealed that, for most cells, the deprived eye was ineffective, i.e., did not activate the unit. This effect was increasingly pronounced as the length of deprivation was increased. However, binocular tests revealed that a large fraction of these cells (30-40%) was clearly influenced by and therefore functionally connected to the deprived eye. This interaction was phase-selective, or suppressive and not selective for phase. There was no indication that the connections that remained were of a specific type, i.e., excitatory or inhibitory. Therefore, excitation and inhibition appear equally resistant to the effects of monocular deprivation. However, with long-term deprivation, we find minimal evidence of functional input from the deprived eye. We conclude that the effects of monocular deprivation occur over a considerably longer time period than was previously thought.
在发育的一个易受影响阶段单眼失明的动物会丧失该眼的视觉功能。尽管对这一现象已进行了广泛研究，但对于被剥夺视觉的眼睛与视觉皮层断开连接的机制却知之甚少。一个基本问题是该眼是否仍有输入。我们检验了这样一个假设，即存在来自被剥夺视觉的眼睛到视觉皮层的功能性输入，而这是用标准的单眼交替测试所无法观察到的。我们采用了一种强有力的视觉刺激程序，其中向每只眼睛以及双眼同时呈现大的正弦光栅，且呈现的相对相位或视网膜视差各不相同。单眼和双眼刺激被用于测试单侧被剥夺视觉不同时长（短期、中期或长期）的小猫。第四组小猫作为正常对照进行研究。使用标准方法记录纹状皮层中的单细胞活动。在对感受野进行初步定性探索之后，所有测试和分析都是定量的。正如预期的那样，单眼测试表明，对于大多数细胞而言，被剥夺视觉的眼睛是无效的，即不会激活该神经元。随着剥夺时间的延长，这种效应愈发明显。然而，双眼测试表明，这些细胞中有很大一部分（30% - 40%）明显受到被剥夺视觉的眼睛的影响，因此在功能上与之相连。这种相互作用具有相位选择性，或者是抑制性的且对相位无选择性。没有迹象表明留存的连接是特定类型的，即兴奋性或抑制性的。因此，兴奋和抑制似乎对单眼剥夺的影响具有同等的抗性。然而，长期剥夺后，我们发现来自被剥夺视觉的眼睛的功能性输入的证据极少。我们得出结论，单眼剥夺的影响发生的时间段比之前认为的要长得多。
