The initial comprehensive activity map of the mammalian brain has unveiled groundbreaking revelations regarding decision-making processes.

For many years, neuroscientists aspired to capture neuronal activity throughout the brain at an individual level. However, challenges persist, including the limitations on the number of neurons an electrode can record, the number of electrodes deployable in a single brain, and the number of animals that a solitary lab can study.

To address these hurdles, a collaboration among 12 laboratories is underway, with each conducting identical experiments and recording duplicates to ensure consistency in collected data. This joint effort, tracking the activity of over 650,000 neurons, has resulted in the first comprehensive brain activity map related to complex behaviors.

“This research exemplifies a novel approach to addressing intricate inquiries in contemporary neuroscience,” stated Benedetto de Martino of University College London, who was not a part of this study. “Similar to CERN, which unites physicists to tackle profound issues in particle physics, this project will bring together global laboratories to confront challenges too expansive for individual teams.”

In each facility, mice were trained to maneuver a small LEGO steering wheel to direct a striped target towards the center of the display. The target was easily distinguishable when the stripes contrasted sharply. As contrast dwindled, the target nearly vanished, compelling the mice to rely on prior knowledge to respond accurately for a reward.

Bias was factored into the experiment, impacting the mice’s expectations about the target’s location. For instance, it could appear on either side of the screen. When the bias was inverted, the mice adjusted their expectations accordingly.

The resulting activity map indicates that decision-related processes are dispersed throughout the brain, rather than localized in one specific area. “Many assertions claimed, ‘this region is responsible for this function.’ However, our findings reveal that decision-making involves numerous regions collaborating through a consensus,” remarked team member Alexandre Pouget from the University of Geneva, Switzerland.

Furthermore, the findings support earlier research indicating that decision-related signals form long before an action is executed. Pouget noted that even prior to the commencement of individual experiments, signals linked to forthcoming decisions are evident. These signals accumulate when the target is presented, prompting the mice to move the wheels until a threshold is reached.

The second study reveals that beliefs regarding the target’s position are encoded very early in the brain’s activity. Researchers discovered that whether the signal emerged from the eye or journeyed to the thalamus, the brain’s relay center, advanced expectations regarding the target’s left or right positioning were already established.

This suggests that from the moment sensory information is processed by our brains, it is inherently influenced by knowledge, altering the conscious decision-making process unconsciously, according to Pouget. “While speculative, this may align with what we interpret as intuition,” he added.

Interestingly, the encoding not only captures recent sensory experiences but also seems to document the recent history of choices made. Lawrence Hunt from Oxford University pointed out, “This indicates that our actions and subjective experiences shape our perceptions, rather than the true objective reality.”

Does this imply our decisions are predestined? “The brain and its environment operate as a deterministic system. People often resist this idea, but it is accurate,” Pouget stated. “This means one can predict, to an extent, what actions will be taken before a decision is made. Nevertheless, when new information arises, expectations must be recalibrated, remaining unaware of how the surrounding world will evolve,” he explained.

Looking ahead, researchers are optimistic that the findings and collaborative methodologies will enhance the understanding of conditions like autism. A mouse model of autism suggests these animals struggle to update previous expectations with new information, according to Pouget, which resonates with our behaviors and perceptions.