ARI SHAPIRO, HOST:

Even the tiniest fragment of a human brain contains multitudes, and now researchers have for the first time revealed almost every detail from a bit of brain the size of a grain of sand. NPR’s Jon Hamilton reports on how they did it and what they found.

JON HAMILTON, BYLINE: The study involved a 1 millimeter cube of brain tissue from a woman with severe epilepsy. Viren Jain, a scientist at Google Research, says surgeons hoped to reduce the woman’s seizures by eliminating a small area of brain behind her left ear.

VIREN JAIN: And to get to the part of the brain where they wanted to do the actual surgery, they had to remove other parts of the brain, and that is the tissue that we were able to study.

HAMILTON: Jain says the sample was preserved and stained to help show all the tiny structures, even the ones found inside cells.

JAIN: They cut it into thin slices, and there was about 5,000 of those slices in this particular study. And then they imaged each one of those slices using something called a multibeam scanning electron microscope…

HAMILTON: Which produced lots of very high-resolution images. Jain says computers and artificial intelligence helped stitch together all those pictures.

JAIN: If you’ve ever taken one of those panorama images on your phone, and it’s sort of guiding you through taking multiple overlapping images to create a single image – so that’s basically what’s going on here, except there’s 300 million individual images.

HAMILTON: All assembled into a three-dimensional representation that is about a million times more detailed than a typical MRI of the brain. Jain says that superfine resolution reveals every synapse – the place where signals in the brain jump from one neuron to another.

JAIN: The reason we think that’s so important is because you really want to understand how the nervous system is computing information, sharing information among cells, storing memories, etc. That is the hardware that’s achieving those functions.

HAMILTON: This unprecedented view of the brain’s hardware, published in the journal Science, has already led to several new observations. Jain says one involves the way neurons communicate.

JAIN: Some pairs of neurons in the brain formed not just one connection between them, but actually up to 50 different connections – in other words, 50 different points of communication between them.

HAMILTON: It’s a bit like stringing 50 separate phone lines between two houses instead of using just one. Jain says this approach might allow ultrafast communication between two brain cells or reduce interference from unwanted signals. Right now, though, it’s just not clear.

Jain says another discovery was that axons – the tail-like fibers that carry outbound messages from a neuron – sometimes tie themselves into a sort of knot.

JAIN: We’ve never seen these before. We don’t really know what their function is, and that’s something to follow up on as well.

HAMILTON: A key goal of the project is to give scientists everywhere access to a highly detailed view of human brain tissue. So Google has developed a freely available web-based app called Neuroglancer. Forrest Collman of the Allen Institute in Seattle says it’s a bit like Google Maps for the brain.

FORREST COLLMAN: And one of its really cool features is the same feature you use in Google Maps all the time. When you go and you find a place, you often copy a link to that place and then send it in an email and be like, let’s meet there.

HAMILTON: Collman says brain researchers are already using the software to compare notes on the fragment of brain tissue.

COLLMAN = ASSISTANT INVESTIGATOR, ALLEN INSTITUTE: We find something interesting, and we are sending Slack messages to one another with these Neuroglancer links. And then as soon as someone clicks on it – boom – they’re looking at exactly the same thing.

HAMILTON: Collman says that should speed up efforts to understand both healthy brain circuits and those affected by a range of psychiatric disorders.

COLLMAN = ASSISTANT INVESTIGATOR, ALLEN INSTITUTE: We do this research to lay a very basic understanding of how things exist in a normal brain so that you can put the things that are going wrong into context.

HAMILTON: Which could lead to a better understanding of brain diseases, like Alzheimer’s.

Jon Hamilton, NPR News.

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