Anatomical origins of ocular dominance in mouse primary visual cortex.
Anatomical origins of ocular dominance in mouse primary visual cortex.
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DOI：
10.1016/j.neuroscience.2009.03.045
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发表时间：
2009-06-30
期刊：
影响因子：
3.3
通讯作者：
Bear, M. F.
中科院分区：
文献类型：
--
作者：
Coleman, J. E.;Law, K.;Bear, M. F.
关键词：
眼优势（Ocular dominance，OD）可塑性是研究经验和剥夺对皮层发育影响的经典范式，表现为双眼输入到初级视皮层（V1）的相对强度的变化。小鼠已成为一个越来越受欢迎的模型OD可塑性的机制研究，因此，重要的是，我们了解如何在这个物种的双目构造。小鼠视觉系统的一个令人困惑的特征是V1中每只眼睛的生理强度与它们在从视网膜到背外侧膝状体核（dLGN）的投影中的解剖表示之间的显著差异。虽然双眼V1中视觉诱发反应的对侧与同侧（C/I）比为1.02：1，但同侧视网膜投影在视网膜神经节细胞（RGC）密度方面表现较弱，其中C/I比为1.09：1。视网膜和V1之间同侧眼反应相对放大的结构基础尚不清楚。在这里，我们采用神经解剖跟踪和形态测量技术，以量化的相对大小，每只眼睛的输入和输出的双眼段的dLGN。我们的数据与之前的建议一致，即双眼观察空间中的一点将激活对侧视网膜中9倍于同侧视网膜中的RGC。尽管如此，对侧retinogeniculate输入所占据的dLGN双眼段的体积仅比同侧retinogeniculate输入所占据的体积大2.4倍，并且受体中继细胞均匀地分布在输入层之间。从我们的形态学分析的结果表明，这种输入量的减少可以占对侧眼RGC输入dLGN神经元的3比1的收敛。总之，我们的研究结果建立了前馈dLGN输入的相对密度决定了小鼠双眼V1的C/I响应比。
Ocular dominance (OD) plasticity is a classic paradigm for studying the effect of experience and deprivation on cortical development, and is manifested as shifts in the relative strength of binocular inputs to primary visual cortex (V1). The mouse has become an increasingly popular model for mechanistic studies of OD plasticity and, consequently, it is important that we understand how binocularity is constructed in this species. One puzzling feature of the mouse visual system is the gross disparity between the physiological strength of each eye in V1 and their anatomical representation in the projection from retina to the dorsal lateral geniculate nucleus (dLGN). While the contralateral-to-ipsilateral (C/I) ratio of visually evoked responses in binocular V1 is ∼2:1, the ipsilateral retinal projection is weakly represented in terms of retinal ganglion cell (RGC) density where the C/I ratio is ∼9:1. The structural basis for this relative amplification of ipsilateral eye responses between retina and V1 is not known. Here we employed neuroanatomical tracing and morphometric techniques to quantify the relative magnitude of each eye’s input to and output from the binocular segment of dLGN. Our data are consistent with the previous suggestion that a point in space viewed by both eyes will activate 9X as many RGCs in the contralateral retina as in the ipsilateral retina. Nonetheless, the volume of the dLGN binocular segment occupied by contralateral retinogeniculate inputs is only 2.4X larger than the volume occupied by ipsilateral retinogeniculate inputs and recipient relay cells are evenly distributed among the input layers. The results from our morphometric analyses show that this reduction in input volume can be accounted for by a 3-to-1 convergence of contralateral eye RGC inputs to dLGN neurons. Together, our findings establish that the relative density of feed-forward dLGN inputs determines the C/I response ratio of mouse binocular V1.
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