The vagus nerve is the fastest and most important route from the gut to the brain. It runs through the diaphragm, between the lungs and the heart, up along the esophagus, through the neck to the brain. Experiments on humans have shown that people can be made to feel comfortable or anxious by stimulating their vagus nerve at different frequencies. In 2010, the European Union approved a medical treatment that uses stimulation of the vagus nerve to help patients suffering from depressive disorders.
