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摘要 : 视网膜的 “星爆无长突细胞” (SAC)树突在计算运动视觉刺激之检测的方向选择性中扮演一个必不可少的角色。

 视网膜的 “星爆无长突细胞” (SAC)树突在计算运动视觉刺激之检测的方向选择性中扮演一个必不可少的角色。过去关于SAC解剖情况的研究工作大多涉及野兔的视网膜。现在,Kevin Briggman及同事发表了在单突触层面对小鼠视网膜所做的一次大规模重建,它显示抑制性和激发性输入突触在SAC树突上的分布存在明显的非对称性。通过电脑模拟和进一步的生理成像,本文作者发现,小鼠特定的视网膜回路适应了其与野兔相比较小的眼睛大小。如果没有这种适应性,那么小鼠将看不见慢速运动的物体。


Species-specific wiring for direction selecivity in the mammalian retina


Directionally tuned signalling in starburst amacrine cell (SAC) dendrites lies at the heart of the circuit that detects the direction of moving stimuli in the mammalian retina. The relative contributions of intrinsic cellular properties and network connectivity to SAC direction selectivity remain unclear. Here we present a detailed connectomic reconstruction of SAC circuitry in mouse retina and describe two previously unknown features of synapse distributions along SAC dendrites: input and output synapses are segregated, with inputs restricted to proximal dendrites; and the distribution of inhibitory inputs is fundamentally different from that observed in rabbit retina. An anatomically constrained SAC network model suggests that SAC–SAC wiring differences between mouse and rabbit retina underlie distinct contributions of synaptic inhibition to velocity and contrast tuning and receptive field structure. In particular, the model indicates that mouse connectivity enables SACs to encode lower linear velocities that account for smaller eye diameter, thereby conserving angular velocity tuning. These predictions are confirmed with calcium imaging of mouse SAC dendrites responding to directional stimuli.

来源: Nature 浏览次数:0


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