Researchers have created the first comprehensive activity map of a mammal’s brain, changing how we understand decision-making. This huge project included over a dozen labs and analyzed data from more than 600,000 individual mouse brain cells, covering over 95% of the brain. Findings, published in two papers in Nature, show that decision-making engages many more areas of the brain than we used to think.
The International Brain Laboratory (IBL) led this initiative. This group brought together scientists from Europe and the U.S. who shared concerns about existing research methods. Matteo Carandini, a key member from University College London, noted that past studies had inconsistencies. Different labs used varied methods and tested different mice, which made it tough to compare results effectively.
Carandini explained the challenge: “We didn’t know if we agreed or disagreed because of these differences.”
To solve this, the IBL designed a standardized experiment that no single lab could manage alone. They paired this with advanced brain measurement tools, aiming for clear and repeatable results. Federico Turkheimer, a neuroscientist at King’s College London, underscored the aim: understanding how differences in brain structure connect to behavior.
For this project, researchers worked with 139 mice implanted with Neuropixels probes, devices that can record activity from about 1,000 neurons at once. The test involved a simple task where a flashed marker indicated a direction. Mice that moved a wheel in the right direction earned a reward.
Initially, researchers expected that brain activity would follow a straightforward path: visual areas would activate first, followed by decision-making areas, and then muscle-control regions. Surprisingly, they discovered that many brain regions were involved. Carandini remarked, “We found decision signals in far more areas than expected.”
In some cases, the marker was dim, requiring mice to guess the movement direction. Another paper focused on how mice used prior experiences to inform these guesses, revealing widespread brain activity during the process.
Drawing parallels from other fields, Carandini likened their research to particle physics at CERN or the Human Genome Project. He explained that earlier brain research often resembled astronomers looking at different stars without a full view. This project allowed them to observe all brain activity collectively.
The findings were made possible thanks to technological advances and better collaboration. However, Carandini pointed out that the observed brain activity is correlational. They can’t yet determine if it directly causes a decision. “The next frontier,” he concluded, “is to add causality to the study.”
This research opens new pathways for understanding the brain. As technology evolves, we might finally grasp the intricate relationships between brain activity and decision-making. It’s an exciting time for neuroscience, one that could reshape our understanding of how we think.
