The impressive “lighting up” of neurons in the brain during decision making
In an unprecedented international effort, neuroscientists from 22 different laboratories have come together to create a neural “map” that illustrates brain activity during decision-making processes.
The data, gathered from 139 mice, documents the activity of over 600,000 neurons across 279 different regions of the brain. This covers approximately 95% of a mouse’s brain. This “map” is the first of its kind to provide a comprehensive view of the brain’s activity at the exact moment a decision is made.
“They’ve created the largest dataset imaginable at this scale,” stated Dr. Paul W. Glimcher, Chairman of the Department of Neuroscience and Physiology and Director of the Neuroscience Institute at New York University’s Grossman School of Medicine.
“This will be remembered as a significant milestone in the field of neuroscience,” Glimcher told CNN.
To create this “map”, the researchers first established a standardized procedure that was shared across all participating labs. They then recorded neural activity as the mice responded to visual stimuli, integrating all the collected data. The project, which spanned seven years, was presented in two studies published on September 3 in the journal Nature.
“There are essentially two major findings, which is why we have two papers,” explained Alexandre Pouget, Professor of Basic Neuroscience at the University of Geneva. One study details the widespread distribution of electrical activity related to decision making, while the other uses the data to investigate how expectations can influence choices.
“We started from scratch,” Pouget said. “No one had ever attempted anything like this before.”
Preliminary research suggested that small clusters of neurons are only activated in certain parts of the brain during decision making, primarily in areas related to sensory processing and cognitive function. However, the new map reveals that activity is far more widespread, with electrical signals firing across almost the entire brain at various stages of the decision-making process.
From Single Neurons to Thousands Simultaneously
For decades, scientists have been studying brain activity during specific tasks using electrodes that record pulses from individual neurons. The previous method was laborious and time-consuming, requiring months of work to gather data from merely 100 neurons, thus limiting its usefulness to very specific areas.
Over the past decade, the field of neuroscience has advanced significantly with the advent of Neuropixels, digital neural probes capable of monitoring thousands of neurons at once. These high-precision electrodes have played a crucial role in crafting the new brain map.
“We’ve progressed from tracking a few hundred neurons in one area to monitoring 600,000 neurons across the entire brain,” explained Pouget. During the experiments, mice were equipped with “helmet-electrodes” and tasked with manipulating a small steering wheel to move a black-and-white circle on a screen. If they successfully guided the circle to the center, they were rewarded with sugar water. As the mice responded, Neuropixels detectors recorded the electrical signals in their brains, first in the visual centers at the back of the brain, then in the movement areas, and finally in the extended networks when they received the reward.
The Role of “Prior Knowledge”
The researchers introduced an extra challenge: occasionally, the circle would appear very faint or nearly invisible. To determine which direction to turn the wheel, the mouse had to recall what it had observed in previous attempts.
“This is what we refer to as prior knowledge,” said Pouget. “Every decision we make is based on this process.”
Neuroscientists had previously theorized that the brain employs prior knowledge very early in the decision-making process. “As soon as you begin processing a sensory stimulus, you do it based on what you anticipate,” added Pouget.
He noted that the new brain map confirmed this hypothesis.
Information sourced from CNN
