A Leap Forward to Understanding How the Brain Works

A milestone in neuroscience has been achieved with the world’s first wiring diagram of every neuron in an adult fly brain, along with the 50 million connections between them. This is a critical step in understanding how brains work.

“If we want to understand how the brain works, we need a mechanistic understanding of how all the neurons fit together and let you think,” explains study co-author Dr. Gregory Jefferis. “For most brains, we have no idea how these networks function.”

To create the first complete wiring diagram, or “connectome,” the less-than-a-millimetre-wide brain was cut into 7,000 thin slices. All those slices were then scanned using high-resolution electron microscopy to extract all 139,255 neurons and 50 million connections between them. Previous studies have been conducted on smaller brain systems, such as the fruit fly brain, which has 3,016 neurons, and the nematode worm, which has 302 neurons. Comparatively, the human brain has 86 billion neurons, and many of the fruit fly’s biological processes are similar to those in humans. The project included experts from the MRC Laboratory of Molecular Biology, Princeton University, the University of Vermont, and the University of Cambridge.