Neuroscience research reveals unexpected role of dopamine in reshaping reward memories

New research has uncovered an unexpected function of dopamine, a brain chemical traditionally associated with pleasure and motivation. Scientists found that dopamine plays a role in reducing the value of memories linked to rewards, suggesting that it can help reshape past experiences in ways that influence future behavior. The findings, published in Communications Biology, challenge long-standing theories about how dopamine functions in learning and memory.

Dopamine is a neurotransmitter—a chemical messenger in the brain—that plays a key role in motivation, pleasure, and reinforcement learning. It is often described as the brain’s “feel-good” chemical because it is released during rewarding experiences, such as eating, social interactions, and other pleasurable activities. Dopamine helps animals, including humans, predict future rewards based on past experiences. Traditional theories suggest that dopamine is involved in reinforcement learning through a process called reward prediction error. This means that dopamine signals help adjust expectations when there is a mismatch between expected and actual rewards.

However, new evidence suggests that dopamine may have a more complex role beyond simple reward signaling. Some studies indicate that dopamine may help encode detailed sensory information about rewards, influencing not only how much we value a reward but also the way we remember and associate it with different experiences. The new study was designed to explore whether dopamine plays a role in modifying reward-related memories and, if so, how this process works.

“The function of dopamine has always fascinated me. It’s been implicated in a vast array of learning and motivation processes, whereas dysfunction of the dopamine system is associated with many mental disorders. Accordingly, understanding more about the nature of dopamine encoding can have wide-reaching implications,” said study author Alex Johnson, an associate professor at Michigan State University.

To test their hypothesis, the researchers used mice in a controlled experiment. They trained the mice to associate an auditory cue with a sweet-tasting food. The sound signaled the arrival of the reward, helping the mice form a strong connection between the cue and the experience of consuming the treat. Later, when the mice heard the same cue, their brains retrieved the memory of the food, even though the food itself was not present.

At this point, the researchers introduced an unexpected twist. Instead of giving the mice the food, they administered a mild treatment that made them feel temporarily unwell. This was similar to how humans might feel after eating something that causes an upset stomach. The key aspect of this experiment was that the mice were not directly consuming the food at the time they felt unwell—they were only recalling the memory of the food.

When the mice had fully recovered, their behavior had changed. They reacted to the sweet-tasting food as if it had made them sick, even though the food itself had never been paired with the illness. This suggested that altering the memory of the food was enough to change how the mice valued it in the future. Instead of associating it with a positive experience, the food now seemed less appealing.

The researchers wanted to identify which brain mechanisms were responsible for this effect. By using specialized techniques to track and manipulate brain activity, they discovered that dopamine-producing cells played a critical role in this process. When they artificially reactivated the dopamine cells that had been engaged during the memory retrieval phase, the mice displayed an even stronger reduction in their preference for the sweet food. Conversely, when the researchers blocked dopamine activity in these cells, the mice did not show the same memory-based devaluation of the food.

“We were able to show that dopamine encodes and reshapes how we process memories associated with reward,” Johnson told PsyPost. “This is important as it tells us that dopamine can play a more elaborate role in learning than originally proposed and may offer the potential in the future to devalue memories associated with certain problematic behaviors, such as those seen with addiction and other neuropsychiatric conditions.”

The findings were surprising because they contradicted the traditional view of dopamine as a simple reward signal. Instead, dopamine appeared to be actively reshaping the memory of the reward, reducing its appeal based on new information. The researchers also used computational models to simulate how dopamine signals might contribute to this process, providing further support for their findings.

“Our study is particularly striking in that we were able to reveal a role for dopamine using a variety of different techniques, each of which revealed a critical role for dopamine in memory devaluation,” Johnson said. “This included labelling, reactivating, inhibiting and recording dopamine circuitry, as well as accurately predicting how dopamine would go about this role through computational modeling.”

While this study sheds new light on dopamine’s role in modifying reward memories, there are limitations. The experiments were conducted in mice, and while the basic mechanisms of dopamine function are shared across species, further research is needed to determine whether the findings apply to humans in the same way. Additionally, the study focused on a specific type of learning and memory—associating a cue with a reward—so it remains unclear whether dopamine has a similar effect in other types of memory processing.

“The study used mice, thus one needs to be cautious in generalizing the findings to humans,” Johnson noted. “Also, it’s unclear whether other approaches could be used to induce a temporary state of malaise for memory devaluation.”

Future studies could explore whether dopamine’s influence on memory extends to more complex behaviors, such as decision-making and habit formation. There is also interest in investigating whether similar mechanisms are involved in conditions like addiction, where problematic reward memories can drive compulsive behavior. Understanding how dopamine reshapes memory could lead to new approaches for reducing the impact of harmful memories, potentially offering new treatment strategies for addiction, eating disorders, and other psychiatric conditions.

The long-term goal of the research is “to further elucidate brain circuitry controlling how we encode rewards in our environment and whether the approaches used in the study could be adopted to help treat neuropsychiatric conditions,” Johnson explained.

The study, “Devaluing memories of reward: a case for dopamine,” was authored by Benjamin R. Fry, Nicolette Russell, Victoria Fex, Bing Mo, Nathan Pence, Joseph A. Beatty, Fredric P. Manfredsson, Brandon A. Toth, Christian R. Burgess, Samuel Gershman, and Alexander W. Johnson.