A team at Baylor College of Medicine did just that, using a mouse engineered with a gene that makes its neurons glow when they’re active. The researchers used a laser-powered microscope to record how individual cells in the animal’s visual cortex lit up as they processed the images flashing by.
Next, scientists at the Allen Institute analysed that small piece of brain tissue, using a special tool to shave it into more than 25,000 layers, each far thinner than a human hair. With electron microscopes, they took nearly 100 million high-resolution images of those sections, illuminating those spaghetti-like fibres and painstakingly reassembling the data in 3D.
Finally, Princeton University scientists used artificial intelligence to trace all that wiring and “paint each of the individual wires a different colour so that we can identify them individually,” Collman explained.
They estimated that microscopic wiring, if laid out, would measure more than five kilometres. Importantly, matching up all that anatomy with the activity in the mouse’s brain as it watched movies allowed researchers to trace how the circuitry worked.
The Princeton researchers also created digital 3D copies of the data that other scientists can use in developing new studies.
Could this kind of mapping help scientists eventually find treatments for brain diseases? The researchers call it a foundational step, like how the Human Genome Project that provided the first gene mapping eventually led to gene-based treatments. Mapping a full mouse brain is the next goal.
“The technologies developed by this project will give us our first chance to really identify some kind of abnormal pattern of connectivity that gives rise to a disorder,” another of the project’s leading researchers, Princeton neuroscientist and computer scientist Sebastian Seung, said in a statement.
The work “marks a major leap forwards and offers an invaluable community resource for future discoveries,” wrote Harvard neuroscientists Mariela Petkova and Gregor Schuhknecht, who weren’t involved in the project.
The huge and publicly shared data “will help to unravel the complex neural networks underlying cognition and behavior,” they added.
The Machine Intelligence from Cortical Networks, or MICrONS, consortium was funded by the National Institutes of Health’s BRAIN Initiative and IARPA, the Intelligence Advanced Research Projects Activity.
