Researchers have captured the first images of a brain changing its beliefs.

It’s not easy being a brain. Among a host of other very complex tasks, this lump of gray matter is also responsible for accurately representing the surrounding world. Keeping these beliefs as true to reality as possible is literally a matter of life and death. As such, brains come equipped with mechanisms that allow them to ‘update’ their beliefs.

That tidbit likely comes as a surprise to anyone who has ever seen a comment section, however. Experience has thought us that most people hate having their beliefs challenged, and will defend them with a fury. So, what exactly makes a brain change a set of beliefs it holds? Well, a team of UK researchers was also very curious to know, so they set about studying the brains of participants as they changed (simple) beliefs.

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It’s dope(amine)

“We form beliefs about the world based on the information we get from our senses. When our sensory perceptions surprise us, it could mean that the world has changed and this might cause us to update our beliefs,” explains lead researcher Matthew Nour, from the University College London and Kings College London. “For example, if we are told that it’s sunny outside, and then we hear raindrops, then we modify our belief.”

Previous research has suggested that the neurotransmitter dopamine is related to the process of updating representations — at least in rodent brains. However, there was no direct evidence that human brains work through the same process, especially since it was very difficult to reliably measure dopamine functions in living people.

For the study, the team used a fMRI (functional magnetic resonance imaging) machine to peer into the brains of people as they were changing short-term beliefs and later tied these readings to the participants’ dopamine functions.

Volunteers were asked to respond to a series of sounds and images — some of which were meant to surprise. These latter ones, the team’s hypothesis went, would cause the participants to change their beliefs about the task environment, since ‘a surprise’ is something the brain didn’t expect, i.e. didn’t conform to its current beliefs. They used the fMRI scanner to measure changes in brain activity while these beliefs were changing, and measured activity in the dopamine system using PET scans — Positron Emission Tomography, which uses a small amount of radioactive tracer to measure dopamine receptors in the brain.

“We found that two key brain areas of the dopamine system (the midbrain and striatum) appear to be more active when a person updates their beliefs about the world, and this activity is related to measures of dopamine function in these regions,” Nour explains.

This is the first study to establish a direct link between dopamine activity and the process of updating beliefs in humans; the neurotransmitter has previously been linked to learning and the brain’s reward pathway.

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Such findings could have several implications, especially pertaining to drugs or medicine that have a powerful impact on dopamine levels in the brain. Cocaine and amphetamine use, for example, “increase[s] brain dopamine release and can cause significant changes in our perceptions and beliefs about the surrounding world,” the team explains.

The paper could also improve our understanding of the several psychiatric disorders have also been tied to abnormal dopamine function. For example, in the case of schizophrenia, abnormal dopamine activity might impair the brain’s ability to update beliefs from outside input, potentially contributing to symptoms such as delusion.

Still, the findings are far from conclusive right now. The team looked at the brain activity of people changing simple beliefs about the causes of their perceptions. However, it points the way for future research into how the brain supports the formation of more general beliefs.

The paper “Dopaminergic basis for signaling belief updates, but not surprise, and the link to paranoia” has been published in the journal Proceedings of the National Academy of Sciences.