Many animals use visual information to navigate^1,2,3,4, but how such information is encoded and integrated by the navigation system remains incompletely understood. In Drosophila melanogaster, EPG neurons in the central complex compute the heading direction⁵ by integrating visual input from ER neurons^{6,7,8,9,10,11,12}, which are part of the anterior visual pathway (AVP)^{10,13,14,15,16}. Here we densely reconstruct all neurons in the AVP using electron-microscopy data¹⁷. The AVP comprises four neuropils, sequentially linked by three major classes of neurons: MeTu neurons^10,14,15, which connect the medulla in the optic lobe to the small unit of the anterior optic tubercle (AOTUsu) in the central brain; TuBu neurons^9,16, which connect the AOTUsu to the bulb neuropil; and ER neurons^{6,7,8,9,10,11,12}, which connect the bulb to the EPG neurons. On the basis of morphologies, connectivity between neural classes and the locations of synapses, we identify distinct information channels that originate from four types of MeTu neurons, and we further divide these into ten subtypes according to the presynaptic connections in the medulla and the postsynaptic connections in the AOTUsu. Using the connectivity of the entire AVP and the dendritic fields of the MeTu neurons in the optic lobes, we infer potential visual features and the visual area from which any ER neuron receives input. We confirm some of these predictions physiologically. These results provide a strong foundation for understanding how distinct sensory features can be extracted and transformed across multiple processing stages to construct higher-order cognitive representations.

许多动物使用视觉信息来导航^1,2,3,4，但导航系统如何对这些信息进行编码和整合仍不完全清楚。在黑腹果蝇中，中央复合体中的 EPG 神经元通过整合来自 ER 神经元^{6、7、8、9、10、11、12} 的视觉输入来计算航向⁵，这些神经元是前视觉通路 （AVP） 的一部分^{10、13、14、15、16}。在这里，我们使用电子显微镜数据密集重建 AVP 中的所有神经元¹⁷。AVP 由四个神经细胞组成，依次由三大类神经元连接：MeTu 神经元^10、14、15，它们将视叶中的延髓连接到中枢脑前视结节 （AOTUsu） 的小单位;TuBu 神经元^9,16，将 AOTUsu 连接到球神经细胞;和 ER 神经元^{6、7、8、9、10、11、12}，它们将球连接到 EPG 神经元。根据形态、神经类别之间的连接和突触的位置，我们确定了源自四种类型的 MeTu 神经元的不同信息通道，并根据延髓中的突触前连接和 AOTUsu 中的突触后连接进一步将它们分为十个亚型。利用整个 AVP 的连接性和视叶中 MeTu 神经元的树突野，我们推断出潜在的视觉特征和任何 ER 神经元接收输入的视觉区域。我们从生理学上证实了其中一些预测。这些结果为理解如何在多个加工阶段提取和转换不同的感觉特征以构建高阶认知表征提供了坚实的基础。