We have all experienced the emotion of fear. Although what one individual might fear (e.g. rollercoasters or snakes), might be exciting and bring joy to others. Regardless fear is an essential emotion that has helped the human species survive. Fear enables us to meet threatening situations with appropriate physiological responses. For example, in a dangerous situation our heartbeat quickens, the bronchi in our lungs dilate which allows us to intake more oxygen, and our body mobilizes energy stores to the muscles so that we can either fight off the dangerous situation or flee from it.
Individuals who are unable to experience fear are often placed in dangerous or life-threatening situations. On the contrary, excessive fear can become pathological and develop into anxiety disorders like post-traumatic stress disorder or generalized anxiety disorder. Because of this, the body must maintain a fine balance between too little and too much fear. Researchers from the Max Planck Institute of Neurobiology in Germany recently asked the question of, how does the brain communicate with the body to maintain fear within this adaptive range? Their research addressing this question was published in the journal Science earlier this week.
The researchers investigated how fear memories in mice are regulated by a region of the brain called the insular cortex. The insular cortex is known to play a role in emotional regulation. However, the researchers wondered if the insular cortex also received feedback from the body to help maintain fear within the adaptive range. To test this, the researchers experimentally stimulated the vagus nerve, the main nerve that carries information from the body to the brain, including the insular cortex. The researchers found that by disrupting the communication from the body to the brain via vagus nerve stimulation, the balance between too little fear and too much fear in the mice was disrupted.
These findings are the first to show that the insular cortex is critically important for integrating bodily signals in order to maintain the emotion of fear within a healthy range. Future work is needed to understand how these findings can be used to treat individuals with anxiety disorders.