Filling in the fly brain

Scheffer, L.K. et al. eLife (2020) https://doi.org/10.7554/eLife.57443

Drosophila melanogaster may be small, but there are plenty of connections to parse through to understand its brain and how the ~100,000 neurons and millions of synapses within are assembled and communicate to give rise to a behaving fly. A recent effort from an international team of researchers reconstructs the circuity of the fly’s hemibrain, an area of the central brain involved in associative learning and navigation as well as sleep and circadian rhythms.

The dataset, available online at the neuPrintExplorer, includes over 20,000 neurons and 20 million chemical synapses. The team also divides the hemibrain into subregions and assigns cell types — 5,229 based on morphology, and 5,609 based on connectivity, to most of those neurons. Initial analyses suggest there are more potential pathways than identified fly behaviors and indicate ways that the fly brain is different from mammalian versions.