Scientists create the most complex map yet of an insect brain's 'wiring'

Researchers understand the structure of brains and have mapped them out in some detail, but they still don't know exactly how they process data — for that, a detailed "circuit map" of the brain is needed. 

Now, scientists have created just such a map for the most advanced creature yet: a fruit fly larva. Called a connectome, it diagrams the insect's 3016 neurons and 548,000 synapses, Neuroscience News has reported. The map will help researchers study better understand how the brains of both insects and animals control behavior, learning, body functions and more. The work may even inspired improved AI networks.

"Up until this point, we’ve not seen the structure of any brain except of the roundworm C. elegans, the tadpole of a low chordate, and the larva of a marine annelid, all of which have several hundred neurons," said professor Marta Zlatic from the MRC Laboratory of Molecular Biology. "This means neuroscience has been mostly operating without circuit maps. Without knowing the structure of a brain, we’re guessing on the way computations are implemented. But now, we can start gaining a mechanistic understanding of how the brain works." 

To build the map, the team scanned thousands of slices from the larva's brain with an electron microscope, then integrated those into a detailed map, annotating all the neural connections. From there, they used computational tools to identify likely information flow pathways and types of "circuit motifs" in the insect's brain. They even noticed that some structural features closely resembled state-of-the-art deep learning architecture.

Scientists have made detailed maps of the brain of a fruit fly, which is far more complex than a fruit fly larva. However, these maps don't include all the detailed connections required to have a true circuit map of their brains. 

As a next step, the team will investigate the structures used for behavioural functions like learning and decision making, and examine connectome activity while the insect does specific activities. And while a fruit fly larva is a simple insect, the researchers expect to see similar patterns in other animals. "In the same way that genes are conserved across the animal kingdom, I think that the basic circuit motifs that implement these fundamental behaviours will also be conserved," said Zlatic.