Epigenetics and Neurobiology Unit, EMBL Rome, European Molecular Biology Laboratory, Monterotondo, 00015, Italy.
Collaboration for joint PhD degree between EMBL and Université Grenoble Alpes, Grenoble Institut des Neurosciences, La Tronche, 38700, France.
Nat Commun. 2023 Nov 16;14(1):7418. doi: 10.1038/s41467-023-43218-x.
Retinotopy, like all long-range projections, can arise from the axons themselves or their targets. The underlying connectivity pattern, however, remains elusive at the fine scale in the mammalian brain. To address this question, we functionally mapped the spatial organization of the input axons and target neurons in the female mouse retinocollicular pathway at single-cell resolution using in vivo two-photon calcium imaging. We found a near-perfect retinotopic tiling of retinal ganglion cell axon terminals, with an average error below 30 μm or 2° of visual angle. The precision of retinotopy was relatively lower for local neurons in the superior colliculus. Subsequent data-driven modeling ascribed it to a low input convergence, on average 5.5 retinal ganglion cell inputs per postsynaptic cell in the superior colliculus. These results indicate that retinotopy arises largely from topographically precise input from presynaptic cells, rather than elaborating local circuitry to reconstruct the topography by postsynaptic cells.
视皮层排列，就像所有的长程投射一样，可以源于轴突本身或其靶标。然而，在哺乳动物大脑的精细尺度上，潜在的连接模式仍然难以捉摸。为了解决这个问题，我们使用体内双光子钙成像技术，以单细胞分辨率对雌性小鼠视皮层-顶盖（retinocollicular）通路上输入轴突和靶神经元的空间组织进行了功能映射。我们发现，视网膜神经节细胞轴突末梢的视皮层排列近乎完美，平均误差低于 30μm 或 2°的视角。上丘中的局部神经元的视皮层排列精度相对较低。随后的数据驱动建模将其归因于输入的低会聚，在上丘中，每个突触后细胞平均有 5.5 个视网膜神经节细胞输入。这些结果表明，视皮层排列主要源于来自突触前细胞的拓扑精确输入，而不是通过突触后细胞构建局部回路来重建拓扑。
