Neuron-by-neuron mapping of a whole fly brain

Abstract

The brain of fruit flies (Drosophila melanogaster) contains 130,000-200,00 neurons, a more approachable number than the 86 billion of the human brain. Last year, the FlyWire research consortium released the first neuron-level adult fruit fly brain map to help understand how the nervous system processes information. Here we describe our effort adding the FlyWire dataset to NeuroMorpho.Org, an open-access database of >260,000 digital tracings of neural morphologies from multiple species. This operation is particularly challenging due to the sheer number (160,427) of FlyWire reconstructions, the morphological irregularities to fix (e.g. long connections and included side branches) and the complex metadata annotation (cell type and anatomical region). NeuroMorpho.Org currently has 36,276 Drosophila cells (13% of the total content, third most represented species) across 17 brain regions. Developmentally, 72% are from adults, 19.4% from larvae, and 8.6% from pupas or unreported stages. The addition of the FlyWire dataset will make Drosophila the species with the most reconstructions in NeuroMorpho.Org, and 97.4% of those tracings will be from adult flies. By utilizing these morphologies, scientists may gain a better understanding of invertebrate brain architectures, which could help reveal how the key organizational principles evolved in more complex organisms such as mammals.