Horton Jonathan C
Beckman Vision Center, University of California, San Francisco 94143-0730, USA.
Can J Ophthalmol. 2006 Oct;41(5):584-93. doi: 10.1016/S0008-4182(06)80027-X.
Human striate cortex contains an orderly map of the contralateral visual field, which is distorted to make a disproportionate amount of tissue available for the representation of the macula. Engrafted on the retinotopic map is a system of alternating inputs known as ocular dominance columns. These columns consist of interleaved bands of geniculocortical afferents in layer 4C serving either the right eye or the left eye. They can be revealed in humans with a history of prior visual loss in one eye by processing striate cortex for cytochrome oxidase at autopsy. Because their geniculate input is segregated, cells within ocular dominance columns in layer 4C respond to stimulation of one eye only. These monocular cells converge onto binocular cells in other layers, integrating signals from the two eyes. The columns in humans appear similar to those found in many primate species, including the macaque. In the squirrel monkey, however, the occurrence of ocular dominance columns is highly variable. Some squirrel monkeys lack columns, yet they seem to have no impairment of visual function. In animals with weakly expressed columns, one can detect a cortical pattern of metabolic activity corresponding to retinal blood vessels. It appears because visual deprivation from shadows cast by blood vessels induces remodeling of geniculocortical afferents, in a manner akin to the shrinkage of ocular dominance columns from congenital cataract. Although the function of ocular dominance columns is unknown, their metabolism is altered in strabismus, suggesting a role in visual suppression.
人类纹状皮层包含对侧视野的有序图谱，该图谱发生了畸变，从而使大量组织可用于黄斑的表征。在视网膜拓扑图谱上嫁接着一个交替输入系统，即眼优势柱。这些柱子由4C层中分别为右眼或左眼服务的膝状皮质传入纤维的交错带组成。在尸检时通过对纹状皮层进行细胞色素氧化酶处理，可以在有过单眼视力丧失病史的人类中揭示它们。由于它们的膝状输入是分离的，4C层眼优势柱内的细胞仅对一只眼睛的刺激做出反应。这些单眼细胞汇聚到其他层的双眼细胞上，整合来自两只眼睛的信号。人类的这些柱子与在包括猕猴在内的许多灵长类物种中发现的柱子相似。然而，在松鼠猴中，眼优势柱的出现高度可变。一些松鼠猴没有柱子，但它们的视觉功能似乎没有受损。在柱子表达较弱的动物中，可以检测到与视网膜血管相对应的皮质代谢活动模式。它的出现是因为血管投射的阴影造成的视觉剥夺会诱导膝状皮质传入纤维重塑，其方式类似于先天性白内障导致的眼优势柱萎缩。尽管眼优势柱的功能尚不清楚，但它们的代谢在斜视中会发生改变，这表明其在视觉抑制中起作用。
