Research shows that human behavior is driven by rapid changes in dopamine levels

What happens in the human brain when we learn from positive and negative experiences? To answer this question and better understand human decision-making and behavior, scientists study dopamine.

Dopamine is a neurotransmitter produced in the brain that serves as a chemical messenger, facilitating communication between nerve cells in the brain and body. It is involved in functions such as movement, cognition and learning. While dopamine is best known for its association with positive emotions, scientists are also exploring its role in negative experiences.

Now, a new study led by researchers at Wake Forest University School of Medicine was published Dec. 1 in Scientists progress shows that dopamine release in the human brain plays a crucial role in encoding reward and punishment prediction errors. This means that dopamine is involved in the process of learning from positive and negative experiences, allowing the brain to adjust and adapt its behavior based on the results of these experiences.

“Previously, research has shown that dopamine plays an important role in how animals learn from “rewarding” (and perhaps “punishing”) experiences. But little work has been done to directly assess what dopamine does on rapid time scales in the human brain,” said Kenneth T. Kishida, Ph.D., associate professor of physiology, pharmacology and neurosurgery at the Faculty of Medicine. in Medicine from Wake Forest University.

“This is the first study in humans to examine how dopamine encodes rewards and punishments and whether dopamine reflects an “optimal” teaching signal used in the most advanced artificial intelligence research in the world. ‘Today.”

For the study, researchers in Kishida’s team used rapid-scan cyclic voltammetry, an electrochemical technique, combined with machine learning, to detect and measure dopamine levels in real time (i.e. -say 10 measurements per second). However, this method is difficult and can only be performed during invasive procedures such as deep brain stimulation (DBS) brain surgery. DBS is commonly used to treat conditions such as Parkinson’s disease, essential tremor, obsessive-compulsive disorder, and epilepsy.

Kishida’s team collaborated with Baptist neurosurgeons Stephen B. Tatter, MD, and Adrian W. Laxton, MD, of Atrium Health Wake Forest, who are also both faculty members in the Department of Neurosurgery at the College of Medicine from Wake Forest University, to insert a carbon fiber microelectrode. deep into the brains of three participants from Atrium Health Wake Forest Baptist Medical Center who were scheduled to receive DBS to treat essential tremor.

While the participants were awake in the operating room, they played a simple computer game. While they played the game, dopamine measurements were taken in the striatum, a part of the brain important for cognition, decision-making and movement coordination.

During the game, participants’ choices were either rewarded or punished with actual monetary gains or losses. The game was divided into three stages in which participants learned positive or negative feedback to make choices that maximized rewards and minimized penalties. Dopamine levels were measured continuously, every 100 milliseconds, throughout each of the three stages of the game.

“We found that dopamine not only plays a role in signaling positive and negative experiences in the brain, but appears to do so optimally when trying to learn from those outcomes. Which was Also interesting is that it appears as if there may be independent pathways in the brain that separately engage the dopamine system for rewarding or punishing experiences. Our results reveal a surprising result that these two pathways may encode rewarding and punishing experiences on slightly offset time scales, separated by only 200 to 400 milliseconds,” Kishida said.

Kishida believes this level of understanding could lead to a better understanding of how the dopamine system is affected in humans with psychiatric and neurological disorders. Kishida said more research is needed to understand how dopamine signaling is altered in psychiatric and neurological disorders.

“Traditionally, dopamine is often called ‘the pleasure neurotransmitter,’” Kishida said. “However, our work proves that this is not the correct way to think about dopamine. Instead, dopamine is a crucial part of a sophisticated system that teaches our brains and guides our behavior. This dopamine is also involved in teaching our brains about punishing experiences. is an important finding and may open new directions of research to help us better understand the mechanisms underlying depression, addiction, and related psychiatric and neurological disorders.