Neuronal wiring diagram of an adult brain

Neurons in Drosophila are considered to be identifiable across hemispheres and individuals, enabling cell-type classification of all neurons in FlyWire’s brain dataset. Such classification is useful for generating testable hypotheses about circuit function from the connectome. FlyWire community members, many of whom are experts in diverse regions of the fly brain, have shared 133,700 annotations of 114,209 neurons (Supplementary Fig. 9), including comprehensive cell typing in the optic lobe, the majority of sexually dimorphic neurons and sensory neurons, as well as a diversity of cell types throughout the brain, including the SEZ (Fig. 2f). Each neuron in FlyWire is also given a unique identifier on the basis of the neuropil through which it receives and sends most of its information. Curation of these annotations continues, and we invite further community efforts to identify cell types, which can be contributed through Codex (https://codex.flywire.ai).

In addition, matching between cell types identified in the hemibrain and both hemispheres of FlyWire’s brain dataset provides additional annotations for neurons contained in both datasets. Our companion paper provides annotations for more than 8,400 unique cell types via such matching. All cell annotations can be queried in Codex. Some of these have already been mentioned, such as the ‘flow’ annotations of intrinsic versus afferent versus efferent, superclass annotations (Fig. 2), connectivity tags (such as rich club, broadcaster or highly reciprocal), neurotransmitter predictions and left–right annotations for cell body location, in addition to lineages or groups of neurons derived from a single neuroblast.