First-Ever Insect Brain Neuron Map Completed

An international research team led by Johns Hopkins University and the University of Cambridge have completed the most advanced brain map to date, that of a baby fruit fly, Drosophila melanogaster larva. The journal Science published the work on March 10.

The delicate map, which includes 3,016 neurons and the 548,000 connections between them, is an incredible breakthrough in neuroscience that brings scientists closer to a true understanding of the mechanism of thought. 

Related article: Human “Mini-Brains” Transplantation Shows a Way to Cure Blindness 

A New Milestone in Neuroscience Development

The researchers chose the fruit fly larva for several reasons. First, its insect nature shares much of its fundamental biology with humans, including a comparable genetic foundation. In addition, its rich learning and decision-making behaviors make it a useful model organism in neuroscience; thus, having the mapping done will ease future neuroscience research.

Scientists first created high-resolution brain images and manually studied them to find individual neurons by tracing each and linking their synaptic connections.  However, the most challenging part of this work is understanding and interpreting the massive amount of images. A team spent years developing original code to analyze the brain’s connectivity while novel techniques were developed to find groups of neurons based on shared connectivity patterns and therefore analyze how information propagates through the brain.

Shedding Insights on Mapping Mammalian Brains

The history of brain neuron mapping started in the 1970s, and targeted roundworms resulting in a partial map and a Nobel Prize. So far, comprehensive connectomes have only been generated for small species, such as larval sea squirts and larval marine annelid worms, with only hundreds to thousands of neurons in their bodies.

Mapping whole brains is never easy and extremely time-consuming, even with today’s advanced technology. That’s why neuroscience is one of the most mysterious careers. Getting a complete cellular-level picture of a brain requires slicing the brain into hundreds or thousands of individual tissue samples, all of which have to be imaged with electron microscopes before reconstructing all those pieces into a full portrait of a brain. 

It took more than a decade to complete the baby fruit fly’s brain, while the brain of a mouse is estimated to be a million times larger than that of a baby fruit fly, meaning the chance of mapping anything close to a human brain is a task of the next level.

Nevertheless, the good news is that the Johns Hopkins researchers claim their methods apply to any brain connection project, and their code is available to whoever attempts to map an even larger animal brain. Despite the challenges, scientists are willing to collaborate and are determined to take on the mouse, possibly within the next decade. 

Author

Nai Ye Yeat