How to Map a Fly Brain in 20 Million Easy Steps - The New York Times

For years, scientists have been mapping the fly’s neurons and synapses in an effort to create a comprehensive wiring diagram, or connectome, of its brain.Credit...David Scharf/Science Source.

The brain of a fruit fly is the size of a poppy seed and about as easy to overlook.

Since 2014, a team of scientists at Janelia, in collaboration with researchers at Google, have been mapping these neurons and synapses in an effort to create a comprehensive wiring diagram, also known as a connectome, of the fruit fly brain.

By analyzing the connectome of just a small part of the fly brain — the central complex, which plays an important role in navigation — Dr.

The only complete connectome in the animal kingdom belongs to the humble roundworm, C.

Several different teams at Janelia have embarked on fly connectome projects in the years since, but the work that led to the new paper began in 2014, with the brain of a single, five-day-old female fruit fly.

The team then used computer vision software to stitch the millions of resulting images back together into a single, three-dimensional volume and sent it off to Google.

Last year, the researchers published the connectome for what they called the “hemibrain,” a large portion of the central fly brain, which includes regions and structures that are crucial for sleep, learning and navigation.

The connectome, which is accessible free online, includes about 25,000 neurons and 20 million synapses, far more than the C.

The brain region, which contains nearly 3,000 neurons and is present in all insects, helps flies build an internal model of their spatial relationship to the world and then select and execute behaviors appropriate for their circumstances, such as searching for food when they are hungry.

Jayaraman’s lab, analyzed the neurons that send sensory information to the ellipsoid body, a doughnut-shape structure that acts as the fly’s internal compass.

The neurons dedicated to polarization of light also connect to — and are capable of strongly inhibiting — brain cells that provide information about other navigational cues.

The connectome data suggests that certain brain cells, technically known as PFL3 neurons, help the fly pull off this maneuver.

There are limitations to what a snapshot of a single brain at a single moment in time can reveal, and connectomes do not capture everything of interest in an animal brain.

(Janelia’s hemibrain connectome omits glial cells, for instance, which perform all sorts of important tasks in the brain.).

Jayaraman and his colleagues stressed that they would not have been able to infer so much from the connectome if not for decades of prior research, by many other scientists, into fruit fly behavior and basic neuron physiology and function, as well as theoretical neuroscience work.

Of course, one could — and some have — asked why a fruit fly’s brain circuitry matters

Gaining a deep understanding of the fly’s brain “also gives us insights that are very relevant to the understanding of mammalian, and even human, brains and behavior,” he said

The mouse brain contains roughly 70 million neurons, the human brain a whopping 86 billion

But the central complex paper is decidedly not a one-off; detailed studies of regional mouse and human connectomes are currently in the pipeline, Dr