Original version With this story appeared in Quanta Magazine.
It’s slow at night. You’re alone and wandering the empty streets looking for your parked car when you hear footsteps sneaking up behind you. Your heart is beating, your blood pressure is skyrocketing. Goosebumps appear on your arms, sweat appears on your hands. Your stomach tightens and your muscles tense, ready to sprint or fight.
Now imagine the same scene, but without the body’s innate responses to an external threat. Would you still be afraid?
Experiences like this reveal the tight integration of brain and body in creating the mind – a collage of thoughts, perceptions, feelings and personality unique to each of us. The capabilities of the brain itself are astounding. The highest organ provides most people with a lively, sensory perception of the world. It can preserve memories, enable us to learn and speak, and generate emotions and awareness. But those who might try to protect their mind by uploading its data to a computer are missing a critical point: the body is necessary to the mind.
How is this crucial brain-body connection organized? The answer involves a very unusual vagus nerve. The longest nerve in the body, it runs from the brain through the head and torso, giving commands to our organs and receiving sensations from them. Much of the astonishing range of functions it regulates, such as mood, learning, sexual arousal and fear, is automatic and operates without conscious control. These elaborate responses engage a constellation of brain circuits that connect the brain and body. The vagus nerve is, in a sense, a conduit of the mind.
Nerves are usually named for the specific functions they perform. Optic nerves carry signals from the eyes to the brain to enable vision. Auditory nerves carry acoustic information for hearing. However, the best that early anatomists could do with this nerve was to call it a “lagus,” which is Latin for “wandering.” The wandering nerve was apparent to early anatomists, especially Galen, a Greek politician who lived until about AD 216. But understanding its elaborate anatomy and function required centuries of study. These efforts are ongoing: research on the vagus nerve is currently at the forefront of neuroscience.
The most vigorous current research involves stimulating this nerve with electrical energy for strengthening getting to know AND memoryand a wide range of treatments for neurological and mental disorders including migraine, tinnitus, obesity, pain, drug addiction and more. But how can stimulation of a single nerve potentially have such broad psychological and cognitive benefits? To understand this, we need to understand the vagus nerve itself.