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Google Maps Brain Activity with Janelia Research Campus has just achieved a significant breakthrough in brain mapping. They have constructed the most complete high-resolution map of a fly brain and were able to pinpoint millions of connections between 25,000 neurons.

The team at Janelia Research Campus achieved this feat by cutting sections of the fly’s brain into ultra-thin (20-micron) slices, image the pieces with electron streams from a scanning electron microscopes, and stitching them back together. This results in sophisticated highly detailed map with few disruptions so that it is practical to trace neurons through the brain.

The scientists’ goal is to represent part of a fruit fly neuron on different computer display screens with vivid 3D images. Such a wiring diagram reveals the complete circuitry of the different areas in the brain and how they link to one another. This work could help unlock networks involved in the formation of memory or neural pathways that underlie movements.

Gerry Rubin, vice president of HHMI and executive director of Janelia, has championed this project for more than a decade. “It’s a necessary step in understanding how the brain works”, he says. When the project began, Rubin estimated that with the available methods, tracing the connections between every fly neuron by hand would take 250 people working for two decades – what he refers to as “a 5,000 person-year problem.”

Google Maps Brain Connectivity Geek impulse
High-level connectome reconstruction pipeline © Janelia

Today, a team of Janelia researchers report hitting a critical milestone: they’ve traced the path of every neuron in a portion of the female fruit fly brain they’ve dubbed the “hemibrain.” The map encompasses 25,000 neurons – roughly a third of the fly brain, by volume; but its impact is outsized. It includes regions of keen interest to scientists; those that control functions like learning, memory, smell, and navigation. With more than 20 million neural connections pinpointed so far, it’s the biggest and most detailed map of the fly brain ever completed.

With this detailed neural map in hand, scientists will be able to answer more questions about how the brain works. This is an important moment in neuroscience and it is ultimately a stepping stone to understanding brains of larger and more complex organisms.

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