Scientists have discovered that dopamine in a part of the brain called the tail of the striatum helps animals adapt to recurring threats and shift their focus toward rewards.

When an animal encounters a potential threat in its environment, it must focus completely on the danger in order to protect itself. But with repeated exposure, the threat becomes familiar and less important. The animal learns to adapt and shift its focus toward opportunities in its environment, such as food.

How the brain makes this transition has remained unclear until now. Researchers at Hokkaido University have found that dopamine signaling in a brain region called the tail of the striatum helps animals shift from defensive behavior toward reward-seeking behavior.

The study, published in Communications Biology, shows that dopamine activity in this region is initially high when mice first encounter an unpleasant stimulus or potential threat. With repeated exposure, however, the dopamine response gradually decreases as the mice adapt to the threat and shift their attention toward seeking rewards.

“In nature, animals constantly face a dilemma between avoiding threats and seeking rewards,” says Professor Iku Tsutsui-Kimura of Hokkaido University, who led the study. “In our previous work, we showed that dopamine in the tail of the striatum plays a critical role in promoting threat-avoidance behavior. Building on that finding, our new research shows that the gradual decrease in dopamine in this region is also responsible for the transition to reward-seeking behavior. It acts as a ‘switch’ that enables this behavioral shift.”

When threat and reward compete

To uncover how the brain handles competing negative and positive experiences, the researchers exposed mice to three different odors. One odor was followed by water as a reward, another by an unpleasant puff of air, and the third by nothing.

The researchers monitored the mice’s responses to each odor. Blinking indicated that the mice were anticipating the unpleasant air puff, while licking indicated that they were anticipating the water reward.

At first, the mice learned to blink when they smelled the odor associated with the air puff. With repeated exposure, however, they gradually reduced this defensive response as they became familiar with the threat. As they adapted, they could instead focus on the reward, anticipating it earlier and earlier.

This suggested that defensive and reward-learning behaviors may compete for attention. While the mice were focused on avoiding the threat, they were less focused on seeking rewards. As they adapted to the repeated threat, reward learning became more prominent.

Dopamine changes as animals adapt

The researchers found that the dopamine response to a threat, such as the air puff, was initially strong but gradually declined with repeated exposure as the mice adapted.

To test whether this decline caused the adaptation, the researchers manipulated dopamine signaling in the mice’s brains. Using optogenetic tools, they prevented the normal decline in dopamine activity that occurs during adaptation. The mice were then slower to adapt to the repeated air puff and did not seek the reward as effectively.

The findings suggest that dopamine in the tail of the striatum helps focus attention on defensive behavior when a threat is new or important. As the animal adapts to the threat, the dopamine response decreases, allowing attention to shift toward other opportunities, including rewards.

These findings provide new insight into how the brain balances competing demands for attention and switches between defensive and reward-seeking behaviors. The study also points to the potential importance of safer environments, where fewer threats may allow attention to shift toward opportunities for learning, exploration and reward.

Original article:

Funding:

This work was supported by the Japan Society for the Promotion of Science (JSPS) KAKENHI (grant number 25K02415), the JST PRESTO program (grant number JPMJPR22S4), and the JST FOREST Program (grant number JPMJFR241R).

Contacts:

Iku Tsutsui-Kimura
Department of Pharmacology
Graduate School of Pharmaceutical Sciences
Hokkaido University
Email: ikimura[at]pharm.hokudai.ac.jp

Megha Kalra
Public Relations & Communications Division
Office of Public Relations and Social Collaboration
Hokkaido University
Email: en-press[at]general.hokudai.ac.jp