A group of British, American, and German researchers has completed the largest and most complicated brain map to date. This map details every neural connection of a fruit fly at the larval stage. After 12 years of work, they have created a comprehensive, 548,000-connection diagram of the brain. It charts the connections between 3,000 neurons and their axes, including connections between the two halves of the brain. This includes connections between the brain and the ventral nerve cord. The research provides insight into how neuronal movements result in behavior and learning.

Just so you understand how far we are from doing this with the human brain, these 3,000 neurons have over half a million connections. In contrast, the human brain has over 20 billion neurons and trillions of connections!

"If we want to understand who we are and how we think, part of that is understanding the mechanism of thought," says Joshua T. Vogelstein, a biomedical engineer at Johns Hopkins University. "And the key to that is knowing how neurons connect with each other."

To create this magnificent multi-functional map, researchers scanned thousands of slices of the fruit fly's brain with a high-resolution electron microscope. They then carefully connected and numbered every connection between neurons, including those that only connect in one hemisphere, in order to build a connectome.

"The way the brain circuit is structured influences the computations the brain can do," explains neuroscientist Marta Zlatic from the University of Cambridge.

"But, up until this point, we've not seen the structure of any brain except of the roundworm Caenorhabditis elegans, the tadpole of a low chordate, and the larva of a marine annelid, all of which have several hundred neurons."

Watch a video of the actual mapped brain:

The given shape represents neurons connected to one another, and the lines connecting them. The lines connecting neurons are colored differently. A connectome is a diagram of the brain that charts all of its connections. Although scientists have made significant progress charting the brain, they are currently unable to complete a connectome for large animals and humans. All brains are networks of interconnected neurons, and all brains of all species require them to perform diverse and complicated behaviors.

Drosophila melanogaster is a popular scientific research model due to its easy-to-study features, complicated yet compact brains, and many overlapping biological similarities with humans. Notably, the connecting structures observed by the researchers were determined to be most repetitive in the part of the brain that allows us to learn and remember what we've learned.

The research team suggests that the next step of their project is to learn more about the neural structure that controls certain behaviors, such as learning and decision-making, and to study the whole connectome while the fly is engaged in action.

"It's been 50 years and this is the first brain connectome. It's a flag in the sand," said Vogelstein.

"Everything has been working up to this."