According to a new study published in the journal Science, scientists have generated the first complete map of an insect’s brain and, critically, all of the synaptic wire that ties it together. The resulting map is known as a connectome, and it is a fundamental piece of neuroscience.
“Now we have a reference brain,” said Marta Zlatic, a neurologist at the University of Cambridge and research co-author.
The brain of a fruit fly larva
A fruit fly larva’s insect brain includes exactly 3,016 neurons and 548,000 synapses.
Previous efforts either produced connectomes of creatures with even smaller brains, such as nematodes, or were simply incomplete, but this one is mind-blowingly detailed — and benefits even more from the fact that the brain under review 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,” research co-author and Johns Hopkins University biomedical engineer Joshua Vogelsteinm told NPR.
The connectome was created using the brain of a female fruit fly larva just six hours old. They photographed the brain using an electron microscope for the next year and a half, generating thousands of visual slices that were subsequently synthesized using a specialist computer program.
The researchers were able to map the synapses because of their exact work.
A journey to understanding the brain
“The brain is the physical object that makes us who we are,” Vogelstein explained. “And to fully understand that object, he says, you need to know how it’s wired.”
By tracing that neuronal circuitry, the researchers discovered something unexpected: how similar the left and right sides of the brain were, in stark contrast to the human brain.
That fascinating discovery, however, is merely the tip of the iceberg. The whole connectome could help scientists figure out how an animal’s brain wiring grows and differs, as well as how 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,” Nuno Maçarico da Costa, an associate researcher at the Allen Institute who was not involved in the study, told NPR.
While the brain of a fruit fly pales in comparison to the complexity of a human brain, which has roughly 100 billion neurons and 100 trillion synapses, this is an important step toward someday mapping the human brain in its entirety.
Source study: Science—The connectome of an insect brain