What happens in the brain when we make a decision? A large consortium of neuroscientists unveils the first comprehensive brain activity map of this complex process in mice.
With never before achieved cell-by-cell resolution, this brain map challenges the traditional hierarchical view of information processing in the brain. It demonstrates that the brain is capable of coordinating numerous regions to simultaneously process different external stimuli, but also of making predictions based on previous experiences in order to make its decision. These results are the subject of two articles published in Nature.
© Dan Birman. IBL
Officially launched in 2017, the IBL introduced a new model of collaboration in neuroscience which pools a standardized set of tools and information management between several laboratories, thus guaranteeing the reproducibility of data. “Thanks to this collaboration ofwingspan21 laboratories worked together on the same experimental model to record theactivity individual of more than 650,000 neurons distributed in 279 areas of the brain, or 95% of the brain volume of the mouse”, details Alexandre Pouget, full professor in the Department of Fundamental Neurosciences at the Faculty of medicine from UNIGE and co-founder of IBL.
There is constant communication between different areas of the brain during the entire decision-making process.
A brain lit up like a Christmas tree
The scientists used Neuropixel probes, a special type of electrode, to simultaneously record neuronal activity and measure the brain activity of mice performing a decision-making task. Placed in front of a screen, they had to move a small wheel left or right, towards a light appearing sporadically, to receive a reward. But sometimes the light was so dim that the animal had to guess which direction to turn the wheel.
“The mouse then uses the frequency with which the light previously appeared on the left or right to make guesses, which allows us to study how prediction based on previous experience influences perception and decision-making,” says Alexandre Pouget. “And we found that when it’s deciding, the whole brain lights up like a Christmas tree!”
From these experiments was born an extremely detailed map of the brain in a decision-making situation, from the very beginning of the process until the reward is obtained.
Two major discoveries
The research teams then made two major discoveries. First, decision-making signals are distributed throughout the brain. They are not located only in certain specific regions, contrary to the commonly accepted model of a hierarchical decision tree. “There is constant communication between different areas of the brain during the entire decision-making process,” explains the researcher.
Furthermore, prior expectations, that is, what one thinks is likely to happen based on previous experiences, are encoded throughout the brain, not just in areas responsible for cognition. The parts of the brain responsible for processing sensory information or those controlling actions also play a central role in the brain’s ability to anticipate and therefore guide behavioral responses.
These findings are important for understanding certain neuropsychiatric disorders such as schizophrenia and autism, where the management of anticipation and reward appears to malfunction.
“Traditionally, neuroscience studies regions of the brain in isolation. Recording the whole brain now gives us the opportunity to understand how all the pieces fit together,” emphasizes Kenneth Harris, professor of quantitative neuroscience at UCL and one of the key members of the IBL.
Acting for open science
One of the principles governing the IBL is a commitment to democratize and accelerate science, as well as to improve the reproducibility of data. The brain map published here is available to teams around the world, who are already using it for numerous research.
Furthermore, all data from these studies, as well as detailed specifications of the tools and protocols used for data collection, are freely accessible to the scientific community. More details on the IBL website in the sections: Data, Tools, Protocols.