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Here's What a Tiny Fragment of Your Brain Looks Like

A cubic millimeter is, by all accounts, tiny. A mere speck. But with modern technology it's possible to zoom in closely enough to reveal an entire world of wonder.

Close up of human brain tissue
A "pizza slice" of brain tissue | Google Research & Lichtman Lab (Harvard University) | Renderings by D. Berger (Harvard University)

A team of neuroscientists and engineers at Harvard University, assisted by machine learning tools, have managed to map a cubic millimeter volume of the human brain at nanoscale resolution, tracing every neuron, synapse, blood vessel, and supporting cell within the fragment and reconstructing a 3D model of the tissue.

It is the most detailed map of a piece of human brain matter ever created, and it's hoped that it will spur a wave of scientific discovery about neurological disorders, brain structure, and the origins of our behaviour.

“In one respect, our data set is miniscule,” Jeff Lichtman, co-senior study researcher and a neuroscientist and professor of molecular and cellular biology at Harvard University. “But it doesn’t feel small because when you get in it, you see it’s like a gigantic forest. It’s a very tiny forest, but it’s a very, very, very complicated forest,” he adds.

A single neuron in the human brain
A single neuron (white) shown with 5,600 of the axons (blue) that connect to it. The synapses that make these connections are shown in green. The cell body (central core) of the neuron is about 14 micrometers across | Credit: Google Research & Lichtman Lab (Harvard University) | Renderings by D. Berger (Harvard University)

“Not only is this an impressive technological feat, this is a tool and a resource that is really aimed at sharing with the world and getting all of this scientific information out there,” says Tim Mosca, a neuroscientist at Thomas Jefferson University who wasn't involved in the project. “This group has done an amazing job designing all of the new tools and the pipelines to make this available to anyone who wants to look at it, wants to think about it, wants to use this in their research.”

The study sample was collected over a decade ago from an anonymous patient undergoing epilepsy surgery. The surgeon removed a small piece of the temporal lobe to access and treat an underlying lesion, quickly preserved the tissue, and later shared it with scientists. Though the total volume of the fragment is about 1 cubic millimeter, it's not actually cube shaped. Instead, “it’s like a thick piece of pizza - but it’s not that thick,” says Lichtman. This blunt, triangular chunk, longer than it is wide, enabled the researchers to capture a bit of all six layers of the 3mm thick cerebral cortex.

“It’s like being an explorer that lands on a new island,” says Lichtman. “You keep looking around and you’re just going to keep finding new things.”



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