On June 6, 2023, Janelia scientists and collaborators in the US and UK unveiled the wiring diagram of the male adult nerve cord, dubbed the MANC. The connectome, a joint effort by Janelia’s FlyEM Project Team, Google and the University of Cambridge, is detailed in preprints on bioRxiv and is freely available to researchers worldwide through Janelia websites.

With about 23,000 neurons, 10 million pre-synaptic sites, and 74 million post-synaptic densities, the MANC is the most in-depth and complete connectome of an adult fruit fly nerve cord – a structure analogous to the human spinal cord that controls most of the fly’s motor functions. The unprecedented detail in this map of neurons and their connections will help scientists figure out how a fly moves its legs or flaps its wings.

The ventral nerve cord includes many different classes of neurons that work together to control behavior. Ascending sensory neurons bring information from the periphery directly to the brain. Most sensory neurons, however, terminate in the ventral nerve cord. Descending neurons carry information from the brain to the ventral nerve cord via the neck connective. Ascending neurons relay information from the nerve cord to the brain, while intrinsic neurons are restricted to the nerve cord and form its largest population. Motor neurons target the muscles to control behavior. This complete, extensively annotated connectome of the adult ventral nerve cord can be used to investigate any neural circuit of interest.

Video by Elizabeth Marin and Philip Hubbard

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