ON and OFF pathways in Drosophila motion vision
ON and OFF pathways in Drosophila motion vision
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DOI：
10.1038/nature09545
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发表时间：
2010-11-11
期刊：
影响因子：
64.8
通讯作者：
Borst, Alexander
中科院分区：
文献类型：
--
作者：
Joesch, Maximilian;Schnell, Bettina;Borst, Alexander
运动视觉是所有视觉系统的一个主要功能，但其潜在的神经机制和回路仍然是难以捉摸的。在黑腹果蝇（Drosophila melanogaster）的第一个视神经堆（lamina）中，光感受器信号分为五个平行的通路，L1-L5（1）。在这里，我们研究这些途径如何有助于视觉运动检测相结合的遗传阻断和重建的神经活动在不同的板层细胞类型与全细胞记录从下游运动敏感神经元（2，3）。我们发现减少响应移动光栅，如果L1或L2被阻止，然而，光感受器输入的重建，只有L1或L2的野生型反应的结果。因此，第一个实验表明了两种途径的必要性，而第二个实验表明了每一种途径的充分性。这种矛盾可以通过L1和L2之间的电耦合来解释，即使只有其中一个接受感光细胞输入，也允许激活两条通路。当阻断L1或L2输出同时呈现正（ON）或负（OFF）对比极性的移动边缘时，L1通路和L2通路之间的根本差异未被揭示：阻断L1消除了对移动ON边缘的响应，而阻断L2消除了对移动OFF边缘的响应。因此，与脊椎动物视网膜中ON和OFF双极细胞通路中的光感受器信号分离类似（4），果蝇的光感受器信号分离到ON-L1和OFF-L2通道中。
Motion vision is a major function of all visual systems, yet the underlying neural mechanisms and circuits are still elusive. In the lamina, the first optic neuropile of Drosophila melanogaster, photoreceptor signals split into five parallel pathways, L1-L5(1). Here we examine how these pathways contribute to visual motion detection by combining genetic block and reconstitution of neural activity in different lamina cell types with whole-cell recordings from downstream motion-sensitive neurons(2,3). We find reduced responses to moving gratings if L1 or L2 is blocked; however, reconstitution of photoreceptor input to only L1 or L2 results in wild-type responses. Thus, the first experiment indicates the necessity of both pathways, whereas the second indicates sufficiency of each single pathway. This contradiction can be explained by electrical coupling between L1 and L2, allowing for activation of both pathways even when only one of them receives photoreceptor input. A fundamental difference between the L1 pathway and the L2 pathway is uncovered when blocking L1 or L2 output while presenting moving edges of positive (ON) or negative (OFF) contrast polarity: blocking L1 eliminates the response to moving ON edges, whereas blocking L2 eliminates the response to moving OFF edges. Thus, similar to the segregation of photoreceptor signals in ON and OFF bipolar cell pathways in the vertebrate retina(4), photoreceptor signals segregate into ON-L1 and OFF-L2 channels in the lamina of Drosophila.