Scientists Establish How Dopamine ‘Tunes’ the Brain

In a recent study, researches linked psychosis with the brain's problems in recognizing and processing information. Defective brain signals of patients with psychosis could then be altered with medication, which will help with new developments of treatment and therapies as scientists focused on dopamine levels and brain activity.

Psychosis, which doctors define as a symptom and not an illness on its own, results in losing touch with reality. This can be the effect of mental or physical illness, trauma, extreme stress, and substance abuse. Someone suffering from psychosis may hear, see, and believe things that are not real.

New research from the University of Cambridge analyzes how dopamine, a chemical messenger, 'tunes' the brain by helping individuals respond to information. Dopamine helps determine if the information is important or not, resulting in updating what people know as reality or distorting it.

The team discovered that it is within the superior frontal cortex region in the brain that signals for various degrees of learning are controlled, depending on the novelty of any given situation. For individuals with psychosis, the superior frontal cortex does not process new information on normal levels, leading patients to believe what is not real.

Novel Situations

Graham Murray from the University of Cambridge's Department of Psychiatry said, 'Novelty and uncertainty signals in the brain are very important for learning and forming beliefs. When these signals are faulty, they can lead people to form mistaken beliefs, which in time can become delusions.'

During a novel situation, the brain compares new information it is receiving to stored memory, creating a gap called the prediction error. When new information is perceived, the brain updates an individual's beliefs according to the size of the prediction error. A large error equates to the brain's perception or belief of the world to be inaccurate which means dopamine affected the 'precision weighting of prediction errors,' notes the study.

In the new research, 20 patients with psychosis were compared to 24 individuals with milder symptoms and 89 healthy people. Using a magnetic resonance imaging (MRI) machine and a computer game, the researchers recorded everyone's brain activity.

Dopamine and Learning

Another part of the study included 59 of the healthy participants having their brain scanned after taking medication that react to dopamine signals in the brain. The medication changed how prediction error responses of the superior frontal cortex became tuned to a degree of uncertainty.

Dr. Kelly Diederen from the Institute of Psychiatry, Psychology & Neuroscience at King's College London, said, 'Normally, the activity of the superior frontal cortex is finely tuned to signal the level of uncertainty during learning. But by altering dopamine signaling with medication, we can change the reactivity of this region. When we integrate this finding with the results from patients with psychosis, it points to new treatment development pathways.'

The mathematical models the team developed of the choices that players of the computer game made revealed that those with psychosis did not consider levels of uncertainty while learning to play the game and making strategies. The learning problems were linked to brain activation alterations, in which the psychosis patients showed significantly higher levels of alterations.

Dr. Joost Haarsma from University College London said that even though the brain responses of psychosis had been predicted years ago, it is only in the new study that the 'changes have actually been shown to be present. The results give us confidence that our theoretical models of psychosis are correct.'