Largest fragment of the human brain mapped

Computer generated image of a section of human brain, neurons are coloured from purple, to red, to yellow, green, and blue in successive layers
Researchers built a 3D image of nearly every neuron and its connections within a small piece of human brain tissue. This version shows excitatory neurons colored by their depth from the surface of the brain. Blue neurons are those closest to the surface, and fuschia marks the innermost layer. The sample is approximately 3 mm wide. Credit: Google Research & Lichtman Lab (Harvard University). Renderings by D. Berger (Harvard University)
May 10, 2024
Imma Perfetto

Imma Perfetto

Cosmos science journalist

Researchers from Harvard University and Google published the largest synaptic-resolution and 3D reconstruction of a piece of human brain to date.

The cubic millimetre of brain tissue is about half the size of a grain of rice but contains 57,000 cells, 230mm of blood vessels, and 150 million synapses.

The resulting digital reconstruction amounts to 1,400 terabytes of data. It is described in a new paper in the journal Science.

Computer generated image of human neurons in varying shades of yellow, blue, and red
This rendering shows all of the excitatory (pyramidal) neurons in a part of the brain sample, at varying degrees of magnification and tilt. They are colored by size; the cell body (central core) of the cells ranges from 15-30 micrometers across. Credit: Google Research & Lichtman Lab (Harvard University). Renderings by D. Berger (Harvard University)

“The word ‘fragment’ is ironic,” says Jeff Lichtman, a professor of molecular and cellular biology at Harvard University, who led the research.

“A terabyte is, for most people, gigantic, yet a fragment of a human brain – just a miniscule, teeny-weeny little bit of human brain – is still thousands of terabytes.”  

The research is the result of a nearly 10-year collaboration between Lichtman’s team and scientists at Google Research, who combine Lichtman’s electron microscopy imaging with AI algorithms to colour-code and reconstruct mammal brains in 3 dimensions. 

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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)

Their ultimate goal is to create a high-resolution map of a whole mouse brain.

This field of research studies the “connectome” which is defined as the “complete, point-to-point spatial connectivity of neural pathways in the brain”.

Creating a comprehensive catalogue of brain structure, down to individual cells, would help provide new insights into brain function and disease.

Shapson coe adk4858 image 7 850
Researchers built a 3D image of nearly every neuron and its connections within a small piece of human brain tissue. Blue neurons are inhibitory neurons. Red, orange, yellow, and green are excitatory neurons colored by size (red is largest, green is smallest) ranging from 15-30 micrometers across at their cores. The sample is approximately 3 mm long. Credit: Google Research & Lichtman Lab (Harvard University). Renderings by D. Berger (Harvard University) Google Research & Lichtman Lab (Harvard University). Renderings by D. Berger (Harvard University)

“Given the enormous investment put into this project, it was important to present the results in a way that anybody else can now go and benefit from,” says co-author Viren Jain, a research scientist at Google Research.

The authors are: “sharing all of the data in an online resource and also providing tools for analysis and proofreading.”

Next up is the mouse hippocampal formation, which is important to neuroscience for its role in memory and neurological disease.

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