Mapping of a Fruit Fly Brain — A Step Closer to Understanding Ours

By Brooklyn Jang

For detrimental diseases of the brain, such as Alzheimer’s, Parkinson’s, and dementia, treatment often focuses on managing symptoms, as no cure currently exists. The reason lies in our limited understanding of the human brain, with billions of neurons connected by a hundred trillion synapses—it is easily one of the most complex systems to unravel.

By building a neuron-by-neuron roadmap through the brain of an adult fruit fly, “FlyWire,” a Princeton-led team of scientists, has now made a massive step towards understanding the human brain (Fuller-Wright). The effort started in 2018 when researchers at the Howard Hughes Medical Institute’s Janelia Research Campus produced an image of a female fly’s brain using electron microscopy. Fly neuroscientist Mala Murthy and computational neuroscientist Sebastian Seung at the Princeton Neuroscience Institute had the idea of using those images to identify and map the connections between each neuron, creating a connectome. This imaging data could be turned into 3D reconstructions of each neuron and its synapses through machine learning; however, the algorithms powering it generated errors so the reconstructions had to be corrected by hand. To do so, Murthy and Seung formed the FlyWire Consortium, a group of research labs worldwide. They built an online platform in 2022 to allow hundreds of volunteers to manually proofread the reconstructions and classify each neuron—a task that the group estimates would have taken a single person 33 years working alone (Ortega). Two years of corrections later, the culmination of their work was featured in Nature on October 2, 2024 (National Institutes of Health).

Previous research of brain mapping efforts included the mapping of a C. elegans worm brain, which had 302 neurons, and the brain of a larval fruit fly, which had 3,000 neurons; but now, with the uncovering of the adult fruit fly, 140,000 neurons and more than 54.5 million synapses are fully charted and understood in unprecedented detail (Reardon). Seung explains, "Any brain that we truly understand tells us something about all brains.” He further emphasizes that this breakthrough could offer opportunities for scientists to explore neural connections in ways that were previously unimaginable (Fuller-Wright). 

Having a full wiring diagram of the fly brain, researchers have taken a big step towards understanding brain function, which could eventually lead to more tailored treatments for neurological diseases. This achievement not only marks a significant milestone in brain mapping research but also showcases the power of interdisciplinary collaboration. The efforts of the FlyWire Consortium combined with the rise of AI to assist in mapping and corrections have made this possible. Sven Dorkenwald, the lead author of the Nature paper and the spearhead of the FlyWire Consortium, remarks, “What we build is, in many ways, an atlas. Just like you wouldn’t want to drive to a new place without Google Maps, you don’t want to explore the brain without a map.” This map, now completed with annotations of the neural connections, is a vital resource for future research to explore the complexities of the fly brain and, ultimately, the human brain.

Works Cited

Fuller-Wright, Liz. “Mapping an Entire (Fly) Brain: A Step toward Understanding Diseases of the Human Brain.” Princeton University, 2 Oct. 2024, www.princeton.edu/news/2024/10/02/mapping-entire-fly-brain-step-toward-understanding-diseases-human-brain.

National Institutes of Health. “Complete Wiring Map of an Adult Fruit Fly Brain.” National Institutes of Health (NIH), 22 Oct. 2024, www.nih.gov/news-events/nih-research-matters/complete-wiring-map-adult-fruit-fly-brain.

Ortega, Rodrigo Pérez. “Complete Map of Fruit Fly Brain Circuitry Unveiled.” Science, 2 Oct. 2024, www.science.org/content/article/complete-map-fruit-fly-brain-circuitry-unveiled, https://doi.org/10.1126/science.zulsbq9.

Reardon, Sara. “Largest Brain Map Ever Reveals Fruit Fly’s Neurons in Exquisite Detail.” Nature, 2 Oct. 2024, www.nature.com/articles/d41586-024-03190-y, https://doi.org/10.1038/d41586-024-03190-y.