Scientists Just Created the First Complete Map of an Insect Brain

Scientists have created the first complete map of an insect’s brain and, crucially, all of the synaptic wiring that connects it together, according to a new study published in the journal Science. The resulting map is known as a connectome, and is an absolute cornerstone of neuroscience.

“Now we have a reference brain,” University of Cambridge neuroscientist and study co-author Marta Zlatic told Nature.

The bug brain belongs to a fruit fly larva, and contains exactly 3,016 neurons and 548,000 synapses.

Whereas previous efforts either produced connectomes of creatures with even smaller brains like nematodes or simply were incomplete, this one is groundbreakingly detailed — and further benefits from the fact that the brain under examination is much more similar to the human brain than previous models.

“There’s regions that correspond to decision making, there’s regions that correspond to learning, there’s regions that correspond to navigation,” study co-author Joshua Vogelsteinm, a biomedical engineer at John Hopkins University, told NPR.

To produce the connectome, the researchers used the brain of a female fruit fly larva that was barely six hours old. For the next year and a half, they imaged the brain using an electron microscope, generating thousands of visual slices that were then synthesized using a specialized computer program.

It was thanks to this painstakingly meticulous work that the researchers were able to map the synapses.

“The brain is the physical object that makes us who we are,” Vogelstein said. “And to fully understand that object, he says, you need to know how it’s wired.”

And by tracing that neural wiring, the researchers realized something unexpected: how similar both the left and right sides of the brain were, markedly unlike a human’s.

That intriguing finding, however, is only the tip of the iceberg. The complete connectome could help answer questions on how an animal’s brain wiring develops and differs, and help scientists figure out ways to “fix” a human one.

“If your radio breaks, if someone has a wiring diagram of your radio, they’ll be in a better position to fix it,” explained Nuno Maçarico da Costa, an associate investigator at the Allen Institute who was not involved in the study, to NPR.

While a fruit fly’s brain pales in comparison to the complexity of a human brain, which contains around 100 billion neurons and some 100 trillion synapses, this is certainly a landmark step towards eventually mapping the human brain in its entirety.