Original version belong to this story appeared in Quanta Magazine.
It was late at night. You are wandering alone on empty streets looking for a parked car when you hear footsteps crawling up from behind. Your heart beats loudly, your blood pressure skyrockets. Goosebumps on the arms, sweat on the palms. Your stomach tightened and your muscles coiled, ready to sprint or fight.
Now imagine the same scene, but without any of the body’s innate responses to an external threat. Would you still feel scared?
Experiences like these demonstrate the close unity between the brain and the body in the formation of the mind – the union of our unique thoughts, perceptions, emotions and personalities. The brain’s capabilities alone are amazing. The supreme organ gives most people a vivid sensory perception of the world. It can store memories, allow us to learn and speak, and create emotions and consciousness. But those who try to protect their mind by uploading its data to a computer miss an important point: The body is essential to the mind.
How is this important connection between the brain and body coordinated? The answer has to do with the very unusual vagus nerve. The longest nerve in the body, it travels from the brain to the head and trunk, giving commands to our organs and receiving sensations from them. The majority of the functions it regulates, such as mood, learning, sexual arousal, and fear, are automatic and operate without conscious control. These complex responses involve a series of brain circuits linking the brain and body. The vagus nerve, in one way of thinking, is the conduit of the mind.
Nerves are often named after the specific function they perform. The optic nerve carries signals from the eyes to the brain to control vision. The auditory nerve transmits sound information to the sense of hearing. However, the best that early anatomists could do with this nerve was to call it “vagus,” from the Latin word for “wandering.” The vagus nerve was known to the earliest anatomists, especially Galen, the Greek scientist who lived until about 216 AD. But it took centuries of research to understand its function. and its complex anatomy. This effort is underway: Research on the vagus nerve is at the forefront of neuroscience today.
The most robust research available today involves electrically stimulating this nerve for enhancement awareness And memoryand a variety of therapies for neurological and psychological disorders, including migraines, tinnitus, obesity, pain, drug addiction, etc. But how does stimulating a single nerve work? could provide such wide-ranging psychological and cognitive benefits? To understand this, we must understand the vagus nerve itself.
The vagus nerve originates from four clusters of nerve cells in the medulla oblongata, where the brain stem attaches to the spinal cord. Most of the nerves in our bodies branch directly from the spinal cord: They are threaded between vertebrae in our spine in a series of lateral tracts to carry information in and out of the brain. But it’s not ambiguous. The vagus nerve is one of 13 nerves that leave the brain directly through special holes in the skull. From there it grows thickets of branches that reach almost anywhere on the head and trunk. The vagus also radiates from two major clusters of nerve outposts, called ganglia, located at key points in the body. For example, a large cluster of vagus neurons clings like vines to the carotid artery in your neck. Its nerve fibers follow this network of blood vessels throughout the body to reach vital organs, from the heart to the lungs to the intestines.
