When you decide to reach for your morning coffee, more than half a million brain cells spring into action across nearly every region of your brain. Scientists have now captured this moment-by-moment neural activity in unprecedented detail, revealing that decision-making is far more brain-wide than researchers once believed.
An international team published two breakthrough studies in the journal Nature showing that making choices involves coordinated activity across the entire brain, not just specialized decision centers. The discovery challenges long-held models of how the brain processes information and could reshape research into conditions like schizophrenia and autism.
International Team Records Activity from 621,733 Brain Cells
Twelve laboratories across Europe and the United States joined forces to record activity from 621,733 individual brain cells in 139 mice. After applying quality-control measures, researchers identified 75,708 well-isolated neurons for their main analyses. Using advanced electrodes called Neuropixels probes, they monitored 279 different brain areas, representing about 95% of the entire mouse brain.
“This is the first time anyone has produced a full, brain-wide map of the activity of single neurons during decision-making. The scale is unprecedented as we recorded from over half a million neurons across mice in 12 labs, covering 279 brain areas, which together represent 95% of the mouse brain volume. The decision-making activity, and particularly reward, lit up the brain like a Christmas tree,” explained Professor Alexandre Pouget, Co-Founder of the International Brain Laboratory (IBL) and Group Leader at the University of Geneva, in a statement.
The experimental task was straightforward: mice watched a screen where a light appeared on the left or right side, then turned a wheel toward the light to receive a reward. On some trials, the light was so faint it was nearly invisible, forcing the mice to guess based on patterns they had noticed in previous rounds.
Brain Activity Spreads Everywhere During Decisions
The brain map challenged the traditional view of neural processing as a tidy assembly line. Instead of sensory areas passing information to decision areas, which then activate motor regions, researchers discovered something far more interconnected.
When mice made decisions, signals appeared simultaneously across the brain. Reward responses activated regions from visual processing areas to movement control centers. Even basic sensory regions showed decision-related activity.
“We’d seen how successful large-scale collaborations in physics had been at tackling questions no single lab could answer, and we wanted to try that same approach in neuroscience. The brain is the most complex structure we know of in the universe and understanding how it drives behaviour requires international collaboration on a scale that matches that complexity,” said Professor Tom Mrsic-Flogel, Director of the Sainsbury Wellcome Centre at University College London and one of the core members of IBL.
This coordinated, brain-wide activity occurred not just during the final act of making a choice, but throughout the entire process of sensing, choosing, and acting.
Brain Makes Predictions at Every Processing Level
The second study revealed where expectations live in the brain. When mice used past experience to guess where the next light would appear, those predictions weren’t confined to higher-thinking areas as many scientists had assumed.
Instead, expectations appeared across the brain, even in the thalamus (the first relay station for visual information from the eyes). This means the brain begins making predictions about what it will see before higher brain regions have even started processing.
The widespread encoding of expectations supports the view that the brain operates as a prediction machine, constantly using past experience to anticipate what comes next. Scientists now know this predictive activity occurs at every level of brain processing, from basic sensory input to motor output.
New Research Directions for Brain Disorders
These discoveries could transform how researchers approach neurological and psychiatric conditions. Schizophrenia and autism, for example, involve difficulties with forming and updating expectations about the world. Knowing that expectations are encoded across the brain, rather than in isolated regions, opens new paths for investigation.
“Traditionally, neuroscience has looked at brain regions in isolation. Recording the whole brain means we now have an opportunity to understand how all the pieces fit together. This was too big of a project for any one lab, and a collaboration on this scale was only possible because of the dedication and talent of our staff scientists, who are the best in the business,” said Dr. Kenneth Harris, Professor of Quantitative Neuroscience at UCL and one of the core members of IBL.
“It’s immensely gratifying to see the IBL deliver the first brain-wide map of neural activity with such high spatial and temporal resolution. The map describes the activity of over 650,000 individual neurons with single-spike resolution. This activity underlies the brain’s sensory and motor activity that constitutes a decision. The map is a fantastic resource that is already being mined by myriad scientists, and yielding unexpected discoveries. It’s a great success for team science and open science,” added Dr. Matteo Carandini, Professor of Visual Neuroscience at UCL and one of the core members of IBL.
Source : https://studyfinds.org/scientists-map-complete-brain-activity-during-decision-making-for-first-time/