Scientists Have Created A Complete Map Of An Insect’s Brain For The First Time - March 17, 2023 at 05:00AM

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You might think that when a fruit fly gets squished, it’s all guts and wings. In truth, it has a brain so complex that scientists from the US, UK, and Germany have spent 12 years visualizing it.

They’ve now finalized their full map, called a connectome, of an insect’s brain—bringing to light, for the first time, a larval fruit fly’s 548,000 connections (AKA synapses) and 3,016 neurons. Admittedly, the bug’s gray matter isn’t as intricate as a human’s, but it’s remarkable nonetheless.

Previously, researchers mapped out 20 million synapses and 25,000 neurons from the brain of an adult fruit fly, but the resulting image was just a partial connectome.

The new, fully-fleshed-out imagery can now serve as a reference map to teach scientists more about how animals’ brains work, the study’s co-author Marta Zlatic, a neuroscientist at the University of Cambridge in England, tells Science News. The team has published its findings, along with the map, in the journal Science.

A baby fruit fly, whose brains are the ones being picked here, is just a fraction of an inch long, the Smithsonian Magazine points out. As for its brain, it’s only about the size of a grain of salt.

Scientists carefully inspected the organ with an electron microscope to visualize thousands of fragments in the brain. It took them a full day to image each neuron, the collaborators at the Johns Hopkins University recount.

After identifying the neurons, they linked them to their associated nerve cells.

In building the colorful map, they discovered that nearly 75% of the most strongly-connected neurons were joined to the brain’s learning center. Accordingly, while there were multiple layers of connections, there were also shortcuts with skipped layers to, presumably, compensate for the fewer neurons.

Interestingly, the left and right hemispheres of the larval fruit fly brain were similar in function with each other. In contrast, the left side of human gray matter is responsible for speech and abstract thinking, while the right half controls attention, memory, and problem-solving.

There are still some similarities between human and fruit fly brains, such as how both of them have areas assigned for learning, decision making, and navigation.

Now that they have a complete picture, the team hopes to better understand how learning and decision-making figures into the insect brain. It also plans to observe the fruit fly’s entire neural activity while the bug is on the move.

[via Smithsonian Magazine and ScienceAlert, images via various sources]