Researchers map the entire brain of an adult fruit fly for the first time

A Princeton-led team of scientists has built the first neuron-by-neuron and synapse-by-synapse roadmap through the brain of an adult fruit fly (Drosophila melanogaster), marking a major milestone in the study of brains. This ...

Previous researchers mapped the brain of a C. elegans worm, with its 302 neurons, and the brain of a larval fruit fly, which had 3,000 neurons, but the adult fruit fly is several orders of magnitude more complex, with almost 140,000 neurons and roughly 50 million synapses connecting them. Fruit flies share 60% of human DNA, and three in four human genetic diseases have a parallel in fruit flies. Understanding the brains of fruit flies is a steppingstone to understanding brains of larger more complex species, like humans.

This is a major achievement," said Mala Murthy, director of the Princeton Neuroscience Institute and, with Sebastian Seung, co-leader of the research team. "There is no other full brain connectome for an adult animal of this complexity." Murthy is also Princeton's Karol and Marnie Marcin '96 Professor of Neuroscience. Princeton's Seung and Murthy are co-senior authors on the flagship paper of the Nature issue, which includes a suite of nine related papers with overlapping sets of authors, led by researchers from Princeton University, the University of Vermont, the University of Cambridge, the University of California-Berkeley, UC-Santa Barbara, Freie Universität-Berlin, and the Max Planck Florida Institute for Neuroscience.

This map shows the precise location and arrangement of the 50 largest neurons of the fly brain connectome. These 50, along with another 139,205 brain cells in the brain of an adult fruit fly, were painstakingly mapped by a Princeton University-led team of neuroscientists, gamers and professional tracers. Activity within these neurons (brain cells) drives everything the organism does, from sensory perception to decision-making to controlling flight. The brain cells are connected by more than 50 million connections (synapses). Credit: Tyler Sloan and Amy Sterling / FlyWire / Princeton University Read more

This image is a video still showing the brain inside an adult fruit fly. Credit: Amy Sterling / FlyWire / Princeton University Read more

This image shows the complete fruit fly connectome: all 139,255 brain cells in the brain of an adult fruit fly. Activity within these neurons drives an entire organism, from sensory perception to decision-making to flying. These neurons are connected by more than 50 million connections (synapses). A Princeton-led team of gamers, neuroscientists and professional tracers painstakingly mapped out the locations and connections of every brain cell, using 21 million images. Credit: Tyler Sloan / FlyWire / Princeton University Read more