original version of this story appeared in Quanta Magazine.
It’s late at night. As you wander alone through the empty streets, looking for a parked car, you hear footsteps creeping up behind you. My heart races and my blood pressure soars. I have goosebumps on my arms and sweaty palms. Your stomach is knotted and your muscles are coiled, ready to sprint or fight.
Now imagine the same scene. However, there is absolutely no innate response of the body to external threats. Do you still feel afraid?
Experiences like these demonstrate the close integration between brain and body in the creation of the mind, a collage of thoughts, perceptions, emotions, and personality that is unique to each of us. The power of the brain alone is astounding. The best organs provide most people with a vivid sensory perception of the world. It can preserve memories, enable learning and speaking, and generate emotions and consciousness. But those who try to preserve the mind by uploading its data to a computer are missing an important point. The body is essential to the mind.
How is this important brain-body connection organized? The answer has to do with the very unusual vagus nerve. The longest nerves in the body travel from the brain through the head and torso to send commands to our organs and receive sensations. The incredible variety of functions the brain regulates, including mood, learning, sexual arousal, and fear, are automatic and operate without conscious control. These complex responses involve a series of cerebral circuits that connect the brain and body. The vagus nerve is, in some ways, a pathway to the mind.
Nerves are usually named according to the specific function they perform. The optic nerve carries signals from the eye to the brain for vision. The auditory nerve carries acoustic information for hearing. But the best the early anatomists could do with this nerve was to call it “vagus,” from the Latin word for “wandering.” The wandering nerve was evident in the first anatomists, especially Galen, a Greek polymath who lived until about 216. But it took centuries of study to understand its complex anatomy and function. These efforts continue. Research on the vagus nerve is at the forefront of neuroscience today.
Currently, the most active research is by stimulating this nerve electrically. recognize and memoryWe offer a variety of treatments for neurological and psychological disorders, including migraines, tinnitus, obesity, pain, drug addiction, and more. But how can stimulating a single nerve potentially have such wide-ranging psychological and cognitive benefits? To understand this, you need to understand the vagus nerve itself.
The vagus nerve originates from a cluster of four neurons in the brain medulla where the brainstem connects to the spinal cord. Most nerves in our body branch directly from the spinal cord. These nerves connect in a series of lateral bands between the vertebrae of the spine and carry information in and out of the brain. But not the vagus nerve. The vagus nerve is one of 13 nerves that exit directly from the brain through a special opening in the skull. From there sprout bushes of branches that reach almost every part of the head and torso. The vagus nerve also emanates from two main clusters of sentinel neurons called ganglia located at important points in the body. For example, a large population of vagus nerve cells clings like vines to the carotid artery in the neck. Nerve fibers follow a network of blood vessels throughout the body, reaching vital organs from the heart and lungs to the intestines.
