How decisions are made by your brain without you realising it

Your brain is working hard before you decide. Without your knowledge, it begins gathering information, weighing your options, and gradually slanting in your favour.

Consider a straightforward scenario: two drivers stuck in traffic at peak hour. The clogged road is visible to both of them. To merge, one presses the gas pedal. The other waits while applying the brakes.

Different responses to the same scene. Why? For years, scientists have been working to find the answer to that question.

The brain's decision-making process

Princeton University researchers may be one step closer to solving the puzzle thanks to collaborations with teams from Boston University, Stanford University, and Cold Spring Harbor Laboratory.

The study focused on how distinct brain cells, each with unique characteristics, work together to form a conclusion. The scientists specifically examined the dorsal premotor cortex, a brain region that facilitates the conversion of decisions into actions.

The dorsal premotor cortex is active when we decide to reach, move, or act. However, this is not as straightforward as one neuron equalling one thought. There is a lot of action here.

Rhesus macaques were educated by the researchers to determine whether green or red was more dominant when they looked at a chequerboard screen. Sometimes it was easy to determine the solution, while other times it was difficult.

Individual neuronal signals

The researchers captured signals from individual neurons while the monkeys made their decisions. The neurones did not act in unison, the researchers discovered, even within the same trial. Scientists refer to this vast range of responses from the monkeys as "heterogeneity."

The study's senior author is Dr. Tatiana Engel, an associate professor at the Princeton Neuroscience Institute. According to Dr. Engel, "it is commonly assumed that this heterogeneity reflects the complex dynamics involved in cognition." Surprisingly, however, we discovered that a completely distinct brain coding theory is responsible for this seeming complexity.

Neurons collaborate to make a choice.

To assist understand this intricacy, the researchers created a novel kind of computer model. It was discovered that two important aspects influence how a neurone behaves. The first is tuning, or the type of decision that triggers a neuron's response. Neural dynamics, or how the brain's internal state affects its activity as it develops over time, is the second.

Picture a terrain that is undulating. Valleys in this concept stand for stable choices. Neurones' patterns move like a ball rolling down a slope when they fire. The ball travels swiftly in the direction of an obvious answer on steeper slopes (easier choices). The ball wobbles more on flatter terrain (harder decisions), increasing the likelihood of errors.

A well-coordinated mental voyage

The team found that this model stood up well when compared to actual brain data. No matter how simple or complex the task, the tuning remained the same, but the mental terrain's contour changed.

This change made it easier to understand why neurons that appear to be random on the surface are acting according to the same fundamental logic.

"Consider it as a team of skiers going down a mountain," Dr. Engel said. "Everyone has a slightly different preferred route, but the slope beneath them shapes them all."

In a similar vein, while every neuron has preferences and activities of its own, the premotor cortex's collective cell group travels in unison and eventually reaches a stable state that symbolises the choice.

Why is this important outside of the lab

The study sheds light on how the brain processes decisions, particularly difficult ones. That kind of understanding is essential for comprehending mental health illnesses as well as daily decision-making.

Bipolar disorder and schizophrenia are two disorders that might interfere with decision-making. Understanding how neurons typically coordinate may assist in identifying the issue. Additionally, it makes it possible to create more specialised treatments that target the brain activity involved in decision-making.

The group is not yet finished. Further investigation into the functions of various neuronal types and how their connections influence this internal environment is their next course of action.

"Every choice is different," Dr. Engel stated. "But we can begin to make sense of it by delving down to the level of individual neurones and trials."