Researchers mapped every neural connection in a fruit fly and found a surprise

The achievement gives the team a new way to examine how the brain and body work together to produce complex actions, including walking and flying. "We can see all of the neurons and their connections as a complete unit for the first time and ask, 'What do we learn from that?'" told reporters paper co-senior author Rachel Wilson, the Joseph B.

First Complete Fruit Fly Brain and Body Wiring Map The new map of neural connections, known as a connectome, extends a earlier on published fruit fly brain connectome by adding the fly's spinal cord equivalent, called the nerve cord. "It is really important to have a central nervous system connectome that is as complete as possible so we can link up the brain and body and start thinking about behavior holistically," explained paper co-senior author Wei-Chung Allen Lee, associate professor of neurobiology at HMS and HMS professor of neurology at Boston Children's Hospital.

When the team studied the connectome, they discovered that many fruit fly behaviors appear to be directed by local neural circuits in the relevant body parts, rather than by one central command area in the brain. One of neuroscience's leading unanswered questions is how neurons in the brain and body connect and coordinate to generate behavior. In 2024, the FlyWire Consortium, led by Mala Murthy and Sebastian Seung at Princeton, who are in addition co-authors of the new research, published a complete connectome of a fruit fly brain.

At the same time, Lee and his colleagues were building a connectome of the fruit fly nerve cord, which controls the legs, wings, and other appendages while in addition processing sensory information. "The brain and nerve cord connectomes are each useful on their own, but until you can bridge the two, it's hard to understand how information moves between the brain and the body," said co-first author Helen Yang, a work fellow in neurobiology in the Wilson Lab.

Co-first author Alexander Bates, in addition a investigation fellow in neurobiology in the Wilson Lab, pointed out that the brain holds most of the neurons, but the nerve cord contains neurons that are "some of the most useful" since they are tied to sensation, movement, and functions that are often easier to interpret. The FlyWire team was eager to shift toward the brain and neural cord, or BANC, dataset imaged in the Lee Lab, told reporters co-senior author Murthy, the Karol and Marnie Marcin '96 Professor of Neuroscience at Princeton and director of the Princeton Neuroscience Institute (PNI).

"The new connectome represents a major advance for the field, with the ability to understand how circuits in the brain receive feedback from and control the actions of the body," she stated. The finished connectome points to how each neuron connects with other neurons in the brain and nerve cord at the level of individual synapses.

The map does not cover the fly's entire body, but the the team used identifiable neurons and previous scientific literature to link central nervous system neurons with neurons in many appendages and sensory organs, effectively "embodying" the connectome. Lee stated the team can use the connectome to develop new hypotheses for lab experiments.

The the team have already used the connectome to paper motor control, especially how a fly moves its legs and other body parts. The same pattern appeared in circuits connected to the fly's wings, mouth, and other body parts.

The scientists as well found that motor circuits connect with other circuit types, including those in the visual and endocrine systems, which supply extra information that helps shape behavior. The authors also acknowledge that the work benefited from the O2 High-Performance Compute Cluster, supported by the Research Computing Group at HMS.