Remember when we would have total control of our problems once we grasped everything we needed to know about the brain? Over the years, with a lot of effort, we have succeeded in learning a lot more about the brain. Recently, a group of Google Research neuroscientists succeeded in mapping a cubic millimetre of human brain tissue. Not a lot, really, just a teeny fragment. Here’s what they said:

“The word ‘fragment’ is ironic,” [Jeff] Lichtman said. “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.”

Harvard University, “Amazingly Detailed Images Reveal a Single Cubic Millimeter of Human Brain in 3D,” EurekAlert, May 9, 2024; Shapson-Coe A, et al. A petavoxel fragment of human cerebral cortex reconstructed at nanoscale resolution. Science. 2024 May 10;384(6696):eadk4858. doi: 10.1126/science.adk4858. Epub 2024 May 10. PMID: 38723085. The paper is not open access but the data is online .

So, in one little dot of brain tissue there is data equivalent to a thousand filing cabinets or 250 movies…? We should remember that when people tell us they have quick and easy cures for issues that originate in the brain.

How did the researchers do it?

The tissue was removed from an epilepsy patient during a surgical procedure. According to NIH,

The team began by cutting the tissue into more than 5,000 slices, or sections, each of which was then imaged by EM. This yielded about 1.4 petabytes, or 1,400 terabytes, of data. Using these data, the researchers generated a 3D reconstruction of almost every cell in the sample. Results of the NIH-funded study appeared in Science on May 10, 2024.

“Unseen details of human brain structure revealed,” National Institutes of Health, May 21, 2024

The NIH Director’s blog tell us us that this sample was particularly valuable because it was normal tissue:

Most biopsies of the brain are done to examine or take out abnormal growths of cells or tissues, making them unsuitable for understanding the normal makeup of the brain. In this case, the researchers were able to obtain a tiny sample from the brain tissue removed and destined for disposal during the normal course of surgery for a patient with epilepsy. The researchers first stained the preserved sample to make the cells easier to trace individually before slicing it into 5,000 thin layers for microscopic imaging.

Dr. Monica M. Bertagnolli, “Most Detailed 3D Reconstruction of Human Brain Tissue Ever Produced Yields Surprising Insights,” May 30, 2024

In all, there were 57,000 cells to study, mostly neurons or glia. But one type of cell, a triangular one found in the innermost depths of the cerebral cortex, was found to have two orientations that are mirror images of each other: “The significance of this organization remains unknown.”

The brain is not what the textbooks told us

There were other surprises too, as science writer Will Sullivan tells us,

The data has already yielded some unexpected findings for the researchers. “There were just so many things in it that were incompatible with what you would read in a textbook,” Lichtman says to MIT Technology Review.

For instance, they found some rare sites where neurons were connected by more than 50 synapses. This is incredibly uncommon—more than 96 percent of connections between neurons have just one synapse, and more than 99 percent have three or fewer synapses, per Google’s blog post.

Will Sullivan, “Scientists Imaged and Mapped a Tiny Piece of Human Brain. Here’s What They Found,” Smithsonian Magazine, May 10, 2024

And there will doubtless be many more surprises to come.

You may also wish to read: Neuroscientist: Human brain more complex than the models show. The weird “homunculus” — the way the brain maps the body — was pioneer neurosurgeons’ best guess nearly a century ago. We shouldn’t be surprised if the brain is more complex than could be known earlier. Most modern research into human beings is turning out that way.