ITHACA, N.Y. – A groundbreaking study by Cornell University has revealed that lab mice experience a significant reduction in anxiety when reintroduced to natural environments. Conducted over two years, the research found that the fear response of these mice, assessed through a classic anxiety assay, was notably diminished or even reversed after just one week in the field.
The study, published on December 15 in Current Biology, parallels findings in human psychology that suggest a broader range of experiences enhances a sense of agency and decreases anxiety levels. “We release the mice into these very large, enclosed fields where they can run around and touch grass and dirt for the first time in their lives,” explained Michael Sheehan, senior author and associate professor of neurobiology and behavior at Cornell. “It’s a new approach to understanding more about how experiences shape subsequent responses to the world, and the hope is that what we learn from these mice will have more generalizability to other animals and to ourselves as well.”
Understanding Anxiety Through the Elevated Plus Maze
The researchers employed the elevated plus maze, a widely used and humane method for studying anxiety in mice. This maze features two arms: one enclosed and safe, and the other open and elevated, exposing the mice to potential threats. Historically, mice have shown a fear response by spending less time in the open arms after initial exposure.
The Cornell team conducted trials where groups of lab mice were exposed to the maze before rewilding half of them. The mice that remained in the lab exhibited the expected fear response, while the rewilded mice displayed a markedly different behavior upon re-exposure to the maze.
“The rewilded mice show either no fear response or a much, much weaker response,” said Matthew Zipple, first author and Klarman Fellow.
Reversing Established Fear Responses
Further findings indicated that mice with an established fear response to the maze could reverse their anxiety after experiencing the field environment. “We put them in the field for a week, and they returned to their original levels of anxiety behavior,” Zipple noted. “Living in this naturalistic environment both blocks the formation of the initial fear response, and it can reset a fear response that’s already been developed in these animals in the lab.”
Zipple emphasized the concept of agency as a core factor in this behavioral change. “What I mean by agency is the ability of an animal to change its experiences in an environment through its own behavior,” he explained. The rewilded mice, able to move freely, burrow, climb, and find food, gain confidence from overcoming challenges, which may enhance their resilience to anxiety-inducing situations.
Implications for Broader Psychological Understanding
The study’s findings resonate with broader psychological theories regarding the impact of varied experiences on anxiety. “If you experience lots of different things that happen to you every day, you have a better way to calibrate whether or not something is scary or threatening,” Sheehan said. “But if you’ve only had five experiences, you come across your sixth experience, and it’s quite different from everything you’ve done before, that’s going to invoke anxiety.”
This research not only provides insights into the behavior of mice but also suggests potential applications for understanding anxiety in humans and other animals. By highlighting the role of environmental factors and experiential diversity, the study opens new avenues for exploring anxiety management strategies.
As the scientific community continues to investigate the intricate relationship between environment and behavior, the Cornell study stands as a testament to the potential benefits of rewilding and experiential diversity. Future research may further elucidate how these findings can be applied to enhance well-being across species.
