A catalogue of neuronal cell types has often been called a ‘parts list’ of the brain¹, and regarded as a prerequisite for understanding brain function^2,3. In the optic lobe of Drosophila, rules of connectivity between cell types have already proven to be essential for understanding fly vision^4,5. Here we analyse the fly connectome to complete the list of cell types intrinsic to the optic lobe, as well as the rules governing their connectivity. Most new cell types contain 10 to 100 cells, and integrate information over medium distances in the visual field. Some existing type families (Tm, Li, and LPi)^6,7,8,9,10 at least double in number of types. A new serpentine medulla (Sm) interneuron family contains more types than any other. Three families of cross-neuropil types are revealed. The consistency of types is demonstrated by analysing the distances in high-dimensional feature space, and is further validated by algorithms that select small subsets of discriminative features. We use connectivity to hypothesize about the functional roles of cell types in motion, object and colour vision. Connectivity with ‘boundary types’ that straddle the optic lobe and central brain is also quantified. We showcase the advantages of connectomic cell typing: complete and unbiased sampling, a rich array of features based on connectivity and reduction of the connectome to a substantially simpler wiring diagram of cell types, with immediate relevance for brain function and development.

神经元细胞类型的目录通常被称为大脑的“零件清单”¹，并被视为了解大脑功能的先决条件^2,3。在果蝇的视叶中，细胞类型之间的连接规则已被证明对于理解苍蝇视觉至关重要^4,5。在这里，我们分析了 fly 连接组，以完成光叶固有的细胞类型列表，以及控制它们连接的规则。大多数新细胞类型包含 10 到 100 个细胞，并在视野中整合中等距离的信息。一些现有的类型系列（Tm、Li 和 LPi）^6,7,8,9,10 的类型数量至少翻了一番。一个新的蛇纹髓 （Sm） 中间神经元家族包含比其他任何类型都多的类型。揭示了 cross-neuropil 类型的三个家族。通过分析高维特征空间中的距离来证明类型的一致性，并通过选择判别特征的小子集的算法进一步验证。我们使用连接性来假设细胞类型在运动、物体和色觉中的功能作用。与跨越视叶和中枢脑的 “边界类型” 的连接也被量化。我们展示了连接组细胞分型的优势：完整和无偏倚的采样，基于连接的丰富特征以及将连接组简化为更简单的细胞类型布线图，与大脑功能和发育直接相关。