People who suffer from post-traumatic stress disorder (PTSD) and other stress- and anxiety-related conditions experience debilitating bouts of fear when they encounter certain environmental cues. In some cases, these bouts of fear come about when cues that merely resemble those that were directly associated with a traumatic or stressful episode are encountered. As a result, individuals find themselves becoming paralyzed with fear when they encounter harmless cues in their environment.

This is called fear generalization, and it can significantly hamper one’s quality of life. The major question for researchers is: What happens in the brain to cause this generalized fear? 

Previous research has focused on the amygdala, prefrontal cortex and hippocampus, all brain regions that monitor and detect threatening stimuli. However, a new study from the Yerkes National Primate Research Center (YNPRC) has demonstrated the zona incerta (ZI), a brain region previously thought insignificant, may play an important role.

Scientists at the YNPRC mapped and manipulated brain activity in the ZI of mice that demonstrated fear toward neutral stimuli of which they should not have been fearful.

Review of the neural activity in the mice’s brains revealed the ZI was less active in mice that showed fear generalization, and stimulating specific cells in the ZI dramatically reduced fear generalization. This suggests the ZI might serve to halt exaggerated fear responses.

These findings could hold therapeutic value for suppressing debilitating fear generalization and helping thousands of people with stress- and anxiety-related disorders live calmer, happier lives.