A fragment of human brain, mapped

Harvard and Google researchers have achieved a significant milestone by creating the largest 3D synaptic-resolution reconstruction of a human brain fragment, measuring just half the size of a rice grain. This intricate piece of human temporal cortex contains 57,000 cells, 230 millimeters of blood vessels, and 150 million synapses, representing 1,400 terabytes of data.

The project, led by Jeff Lichtman, Jeremy R. Knowles Professor of Molecular and Cellular Biology and the new dean of science at Harvard, was carried out in collaboration with Google researchers. They employed advanced electron microscopy and AI algorithms to color-code and analyze the dense and complex neural connections.

This research, part of a long-term partnership spanning nearly a decade, was highlighted in a recent publication in Science. The paper lists Alexander Shapson-Coe, a former Harvard postdoctoral researcher, Michal Januszewski from Google Research, and Daniel Berger, a current Harvard postdoctoral researcher, as its co-first authors.

One of the broader aims of this collaboration, supported by the National Institutes of Health's BRAIN Initiative, is to eventually map the entire neural wiring of a mouse brain at high resolution, which would encompass around 1,000 times more data than the current human brain fragment.

"The word 'fragment' is ironic," Lichtman said. "A terabyte is, for most people, gigantic, yet a fragment of a human brain - just a minuscule, teeny-weeny little bit of human brain - is still thousands of terabytes," commented Jeff Lichtman, emphasizing the scale of the data involved.

The detailed mapping revealed new insights into brain structure, including a unique network of axons linked by up to 50 synapses and some unusual formations potentially related to the sampled patient's epilepsy condition.

The field of "connectomics," akin to genomics, aims to comprehensively catalog brain structures down to the minutest details, offering new pathways to understanding brain functions and diseases-a subject still largely mysterious to scientists.

This collaboration also produced a suite of tools now publicly available for other researchers to explore and annotate the connectome, enhancing the utility and accessibility of the data produced.

"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 them," stated Viren Jain, a collaborator from Google Research.

Looking forward, the team plans to focus on mapping the mouse hippocampal formation, crucial for memory and understanding neurological diseases.

Research Report:A petavoxel fragment of human cerebral cortex reconstructed at nanoscale resolution