Largest, Most Complex Insect's Brain Map Ever Made Shows Neural Connection

Following 12 years of work, a big team of researchers from the United Kingdom, the United States, and Germany have constructed the largest and most complex brain map to date. It documents every neuronal connection in the brain of a larval fruit fly.

While it may not be as big and complex as a human brain, Science Alert reports that it nonetheless covers 548,000 connections between a total of 3,016 neurons.

Connectome: First Complete Brain Map of an Insect

The map shows distinct types of neurons and their routes, as well as connections between the two sides of the brain and the spinal cord. This advances scientists' knowledge of how signal transmission from neuron to neuron leads to behavior and learning.

Joshua T. Vogelstein, a biomedical engineer at Johns Hopkins University, said in a press release that understanding the machinery of the mind is part of knowing humans in the cognitive sense. The key to this is understanding how neurons communicate with one another.

Researchers used a high-resolution electron microscope to scan hundreds of slices of the young fruit fly's brain to produce this stunning multi-functional map, known as a connectome. Scientists then assembled the images and merged them with previously collected data, precisely noting each and every connection between neurons.

This includes both cells that communicate inside each half of the brain as well as those that communicate across the two hemispheres, allowing researchers to examine brain connections in depth.

Although the hemispheres of the brain have distinct and vital tasks, how they integrate and utilize information from each side for complex behavior and cognition is not fully understood.

Marta Zlatic, a researcher at the University of Cambridge, said that the way the brain circuit is built determines the communications that can execute. This is the first time scientists mapped the brain of insects with the exception of Caenorhabditis elegant, a larva of marine annelid, and a low chordate.

Observing Neural Activity of a Larva Fruit Fly

The team chose the larva fruit fly Drosophila melanogaster because it shares much of its fundamental biology with humans, like a comparable genetic foundation, SciTech Daily reports. More so, it is best for learning decision-making behaviors which makes it a useful model organism in neuroscience.

The high-resolution pictures of the brain were made by Cambridge researchers and painstakingly inspected to discover individual neurons, meticulously tracing each one and connecting their synaptic connections.

Cambridge forwarded the data to Johns Hopkins, where the researchers spent more than three years analyzing the brain's connections using the original programming they wrote. The Johns Hopkins scientists devised methods for identifying groupings of neurons based on similar connection characteristics and then investigated how information may spread across the brain.

Finally, the entire team tracked every brain cell and every connection and classified each neuron based on its function in the brain. They discovered that the busiest circuits in the brain were those that went to and from neurons in the learning area.

The methods developed by Johns Hopkins are applicable to any brain connection project, and their code is available to anyone attempting to map an even larger animal brain.

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