Scientists studying anxiety in mice have discovered special neurons that may hold the key to understanding fear responses in humans. Not only were these “anxiety cells” previously unknown, but researchers also found they could suppress or activate them using targeted beams of light. These findings may have significant meaning for understanding and treating anxiety disorders in humans.

Identifying Anxiety In Mice

In 2018, researchers from the University Of California, San Francisco set out to study anxiety in mice. While fear and anxiety can be appropriate responses to threats and danger, excessive anxiety can cause harm. This is easily seen in humans, as anxiety disorders are often accompanied by a feeling of over-exaggerated fear–even when there is nothing concrete to be scare of. (1)

The test set out to examine anxious mice. Using live images of their brains as they navigated a maze, the mice showed increased activity in the hippocampus. This area of the brain is involved in navigation and memory–as well as anxiety. The “anxiety cells” were discovered here.

When the mice went into an area that sparked anxiety–like an open arm of the maze, rather than a closed one–certain cells in the hippocampus became more active. However, the team wanted to be sure that the neurons are what caused the anxiety in the mice. To test their theory, the researchers used a technique called optogenetics. By directing a beam of light to targeted cells, researchers found they could control the signals sent between these neurons and the hypothalamus. At the same time, they could observe the reactions of the mice. (2, 3)

Altering Neural Pathways

With the “anxiety cells” suppressed, the mice did not display the same anxious behavior–even in the open areas that naturally should have caused them fear. Alternatively, turning these neurons “on” made the mice anxious even when they were in a safe, comfortable environment. These findings offer new possibilities for treating humans with anxiety disorders.

Mazen Kheirbek, Ph.D., is an assistant professor of psychiatry. His lab, in partnership with neuroscientist René Hen, Ph.D., conducted the mice experiment. “This is exciting,” Khierbek told the University of California, San Francisco. “It represents a direct, rapid pathway in the brain that lets animals respond to anxiety-provoking places without needing to go through the higher-order brain regions.” These results could help researchers better understand the way anxiety disorders work in humans. If human anxiety neurons function similarly, there could be a way to “turn off” their expression by using optogenetics. (2)

Hope For Human Anxiety Disorders

This study on anxiety in mice adds another piece to the puzzle of anxiety disorders. Understanding them is key, as anxiety disorders affect an estimated 31.1% of U.S. adults at some time in their lives. These anxiety disorders can cause marked impairment in the daily lives of sufferers. By better understanding how these disorders work, more effective treatments could alleviate suffering from those affected. (4)

While scientists will need more studies to correlate the study results to human anxiety, the findings offer an interesting avenue to explore. Targeted therapies like optogenetics could someday alleviate human anxiety disorders. Many more could then experience relief from the overwhelming, exaggerated fears of anxiety disorders.