Summary: Dopamine, a neurotransmitter, plays a vital role in encoding both reward and punishment prediction errors in the human brain.

This study suggests that dopamine is essential for learning from both positive and negative experiences, enabling the brain to adapt behavior based on outcomes. Using electrochemical techniques and machine learning, scientists measured dopamine levels in real-time during a computer game involving rewards and penalties.

The findings shed light on the intricate role of dopamine in human behavior and could have implications for understanding psychiatric and neurological disorders.

Key Facts:

Source: Wake Forest Baptist Medical Center

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

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

Now, a new study from researchers at Wake Forest University School of MedicinepublishedDec. 1 inScience Advancesshows thatdopamine releasein the human brain plays a crucial role in encoding both reward and punishment prediction errors.

This means that dopamine is involved in the process of learning from both positive and negative experiences, allowing the brain to adjust and adapt its behavior based on the outcomes of these experiences.

Previously, research has shown that dopamine plays an important role in how animals learn from rewarding (and possibly punishing) experiences. But, little work has been done to directly assess what dopamine does on fast timescales in thehuman brain, said Kenneth T. Kishida, Ph.D., associate professor of physiology and pharmacology and neurosurgery at Wake Forest University School of Medicine.

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

For the study, researchers on Kishidas team utilized fast-scancyclic voltammetry, an electrochemical technique, paired withmachine learning, to detect and measuredopamine levelsin real-time (i.e., 10 measurements per second). However, this method is challenging and can only be performed during invasive procedures such as deep-brain stimulation (DBS) brain surgery.

DBS is commonly employed to treat conditions such as Parkinsons disease, essential tremor, obsessive-compulsive disorder and epilepsy.

Kishidas team collaborated with Atrium Health Wake Forest Baptist neurosurgeons Stephen B. Tatter, M.D., and Adrian W. Laxton, M.D., who are also bothfaculty membersin the Department of Neurosurgery at Wake Forest University School of Medicine, to insert a carbon fiber microelectrode deep into the brain of three participants at Atrium Health Wake Forest Baptist Medical Center who were scheduled to receive DBS to treat essential tremor.

While the participants were awake in theoperating room, they played a simple computer game. As they played the game, dopamine measurements were taken in the striatum, a part of the brain that is important for cognition, decision-making, and coordinated movements.

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

We found that dopamine not only plays a role in signaling both positive and negative experiences in the brain, but it seems to do so in a way that is optimal when trying to learn from those outcomes. What was also interesting, is that it seems like there may be independent pathways in the brain that separately engage the dopamine system for rewarding versus punishing experiences.

Our results reveal a surprising result that these two pathways may encode rewarding and punishing experiences on slightly shifted timescales separated by only 200 to 400 milliseconds in time, Kishida said.

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

Traditionally, dopamine is often referred to as the pleasure neurotransmitter, Kishida said.

However, our work provides evidence that this is not the way to think about dopamine. Instead, dopamine is a crucial part of a sophisticated system that teaches our brain and guides our behavior.

Thatdopamineis also involved in teaching ourbrainabout punishing experiences is an important discovery and may provide new directions in research to help us better understand the mechanisms underlying depression, addiction, and related psychiatric and neurological disorders.

Author: Kenneth T. Kishida Source: Wake Forest Baptist Medical Center Contact: Kenneth T. Kishida Wake Forest Baptist Medical Center Image: The image is credited to Neuroscience News

Original Research: Open access. Sub-second fluctuations in extracellular dopamine encode reward and punishment prediction errors in humans by Paul Sands et al. Science Advances

Abstract

Sub-second fluctuations in extracellular dopamine encode reward and punishment prediction errors in humans

In the mammalian brain, midbrain dopamine neuron activity is hypothesized to encode reward prediction errors that promote learning and guide behavior by causing rapid changes in dopamine levels in target brain regions.

This hypothesis (and alternatives regarding dopamines role in punishment-learning) has limited direct evidence in humans. We report intracranial, subsecond measurements of dopamine release in human striatum measured, while volunteers (i.e., patients undergoing deep brain stimulation surgery) performed a probabilistic reward and punishment learning choice task designed to test whether dopamine release encodes only reward prediction errors or whether dopamine release may also encode adaptive punishment learning signals.

Results demonstrate that extracellular dopamine levels can encode both reward and punishment prediction errors within distinct time intervals via independent valence-specific pathways in the human brain.

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Dopamine's Role in Learning from Rewards and Penalties - Neuroscience News