But Andrew Huberman, a neuroscientist at Stanford University who studies the visual system, sees matters a bit differently. Stress, he says, is not just about the content of what we are reading or the images we are seeing. It is about how our eyes and breathing change in response to the world and the cascades of events that follow. And both of these bodily processes also offer us easy and accessible releases from stress.
Huberman’s assertions are based on both established and emerging science. He has spent the past 20 years unraveling the inner workings of the visual system. In 2018, for example, his lab reported its discovery of brain pathways connected with fear and paralysis that respond specifically to visual threats. And a small but growing body of research makes the case that altering our breathing can alter our brain. In 2017 Mark Krasnow of Stanford University, Jack Feldman of the University of California, Los Angeles, and their colleagues identified a tight link between neurons responsible for controlling breathing and the region of the brain responsible for arousal and panic.
This growing understanding of how vision and breathing directly affect the brain—rather than the more nebulous categories of the mind and feelings—can come in handy as we continue to face mounting challenges around the globe, across the U.S. and in our own lives. Scientific American spoke with Huberman about how it all works.
Stress is one position along the continuum of what we call autonomic arousal. At one end of this continuum would be somebody in a coma. At the very other end of that continuum is a full-blown panic attack: heart racing, pupils dilating, hyperventilating. In between, we have lower levels of stress, [and the states of being] alert and focused, sleepy, and asleep. Stress is generally a high level of autonomic arousal. It was designed to be a generic response to mobilize the body.
Sometimes that’s well matched to the demands of life. If you need to run and catch your train, you want all the things that go along with stress to go pursue that train. But if the stress response is spontaneous or excessive, it can start to feel pathological.
When you see something exciting or stressful—a news headline, a fraudulent credit card charge—heart rate increases; breathing increases. One of the most powerful changes is with vision. The pupils dilate, and there’s a change in the position of the lens in the eye. Your visual system goes into the equivalent of portrait mode on a smartphone. Your field of vision narrows. You see one thing in sharper relief, and everything else becomes blurry. Your eyeballs rotate just slightly toward your nose, which sets your depth of field and focuses on a single location. This is a primitive and ancient mechanism by which stress controls the visual field.
How does this visual mode affect the body?
This focal vision activates the sympathetic nervous system. All the neurons from your neck to the top of your pelvis get activated at once and deploy a bunch of transmitters and chemicals that make you feel agitated and want to move.
Why is the visual field so connected to this brain state?
Something that most people don’t appreciate is that the eyes are actually two pieces of brain. They are not connected to the brain; they are brain. During development, the eyes are part of the embryonic forebrain. Your eyes get extruded from the skull during the first trimester, and then they reconnect to the rest of the brain. So they’re part of the central nervous system.
Having the eyes outside the skull orients the organism to the time of day. But it also means that you’ve got two pieces of brain that can register events in the environment at a distance in order to adjust the overall state of alertness in the rest of the brain and body. It would be terrible if we had to wait until things were in contact with us before we could prepare to react to them.
You are also researching breathing as a way to regulate autonomic arousal.
Yes. Vision and breathing are, without question, the fastest and most obvious ways to control autonomic arousal. The way we breathe impacts our states of stress very strongly.
Data show that during sleep and claustrophobic states, people and animals generate what are called “physiological sighs,” double inhales followed by exhales. Children also do this when they are sobbing. A physiological sigh, two or three times, is the fastest way that we are aware of to bring the level of autonomic arousal back down to baseline.
Our lungs consist of tons of tiny little sacs of air, millions of sacs of air. As we get stressed, these little sacs collapse. They deflate like a balloon. Physiological sighs cause the sacs to reinflate. Carbon dioxide is the trigger for breathing: We don’t breathe because we need oxygen. We breathe because carbon dioxide levels get too high. Physiological sighs offload the maximum amount of carbon dioxide.
So with vision and breathing, you are looking at physiological processes that are automatic but that we can also control.
Yes. If I make you stressed, you’ll perspire. But you wouldn’t say, “I’m going to make myself sweat, and therefore I’ll be stressed.” You can’t control your heart rate directly. You can’t control your adrenals with your mind. But you can control your diaphragm, which means you control your breathing, which means you control your heart rate, which means you control your alertness. You can control your vision, which thereby controls your level of alertness, your level of stress and your level of calmness.
Vision and breathing are essential as levers or entry points to autonomic arousal because they are available for conscious control at any point.