Alex Honnhold climbs El Capitan in Yosemite National Park, alone and
without ropes, as featured in the documentary 'Free Solo.' He has had his
brain scanned to find how he reacts to fearful situations differently than
most people. Photo: National Geographic/Jimmy Chin

When Dave Henson signed up in 2010 to be a bomb disposal officer with the British Army Royal Engineers in Afghanistan, he knew the risks he would face - a one-in-six chance of death or maiming. When Angie Padron stopped for gas in 2016 in Hialeah, Fla., with her two small children, she didn't have time to think before a masked man approached with a gun pointed at her head while another opened the car door to get in. She fought off both assailants.

Such exceptional bravery impresses us and makes us wonder whether we could ever rise to such feats. But where does bravery come from? What accounts for it?

In recent years, researchers across several fields have examined what happens in our brains when we are challenged by fear or danger. They have learned a great deal not only about the complex biology of bravery but about the possibility of helping all of us to deal more effectively with life's most extreme situations.

Most of the science focuses on the amygdala, the almond-shaped structure deep in the brain (one on each side) that generates such feelings as fear and anxiety. In 2005, a team led by Gleb Shumyatsky at Rutgers University reported in the journal Cell that stathmin, a protein produced by the STMN1 gene, has an important role in the amygdala. Mice that were bred not to have the protein explored more of a new environment. They lacked what the researchers called "innate fear" and were unable to form memories of fear-inducing events.

' We don't want to make people irrationally brave. But fear can be disabling, too. '

The researchers also manipulated the gene as a kind of "volume" control, producing different levels of stathmin, which in turn resulted in different levels of fear in the mice. In 2010, researchers led by Burkhard Brocke at the Institute of Psychology II in Germany found that people with an exaggerated response to fear had mutations in the gene that controls this volume switch.

As for how we overcome fear, scientists have found brain structures that appear to resist the prompting of the amygdala. In a 2010 study published in the journal Neuron, the neurobiologist Uri Nili at the Weizmann Institute in Israel scanned the brains of research subjects who were afraid of snakes as they decided whether or not to move a live snake closer or farther away on a conveyor belt. The more people were able to overcome their fear and move the snake closer, the more activity they showed in the sgACC, a brain region that sits between the amygdala and the hypothalamus, which stimulates the release of hormones. A control group that wasn't scared of snakes didn't show such activity.

Hormones released in the amygdala itself also have been shown to affect bravery. Oliver Bosch, a neurobiologist at the University of Regensburg in Germany, studies maternal instinct in mammals and has found that oxytocin is released in the amygdala when a mother faces a danger to herself and her children. This hormone, in turn, blocks the production of a hormone called CRH, which primes the body for action but can generate feelings of fear and anxiety. It is this sort of hormonal override that would have given Angie Padron, the mother in Florida, the instant courage to confront her assailants. As she herself said of the incident, her instincts just kicked in.

Indeed, taking the amygdala entirely out of the picture can virtually eliminate fear. Justin Feinstein, a clinical neuropsychologist at the Laureate Institute for Brain Research at the University of Tulsa, works with three women, known in the literature just by their initials, who have Urbach-Wiethe disease, a rare genetic disorder that destroys the amygdala. One of them, SM, has never experienced fear in her adult life. A man once threatened her by putting a gun to her head and shouting "Bam!" She didn't flinch.

Of course, it's not necessary to have a brain disorder in order to control one's fear, even in the face of heart-stopping danger. Consider Alex Honnold, the climber who has scaled the 3,000-foot El Capitan in Yosemite National Park without ropes (as featured in the new documentary, "Free Solo") and made other notable ascents. In 2016, Mr. Honnold's brain was scanned by neuroscientist Jane Joseph at the Medical University of South Carolina in Charleston. When exposed to images that excite the amygdala in most people, his brain scans showed no response. What's unclear is whether this capacity predates and enables his daredevil climbing or has been created by it.

' We know, too, that training and conditioning alters pathways in the brain. '

Never feeling fear is dangerous, but as this emerging body of research suggests, modulating the action of the amygdala may offer a way to control responses to threats and fearful experiences. It points the way to potential treatments for, among other things, post-traumatic stress disorder.

But the amygdala isn't the only candidate for controlling fear. In a study published earlier this month in the journal Nature Communications, Sanja Mikulovic and colleagues at Uppsala University in Sweden showed that cells called OLM neurons produce theta brain waves, which are seen during meditation and when you feel safe despite a threat in the environment. By manipulating those cells in laboratory mice, the scientists were able to dial up a mouse's willingness to venture into unexplored areas and tamp down its indications of anxiety, even when smelling a cat. Nicotine also stimulates OLM neurons in humans, a reason that some people chain-smoke to relieve stress.

We know, too, that training and conditioning alters pathways in the brain and can help to mitigate stress and promote calm in fearful situations. A study published in the journal PLOS Biology last year showed, for example, how training instills a kind of autopilot setting. Researcher Sirawaj Itthipuripat at the University of California, San Diego, measured brain activity when people were learning a task and found that less was needed after training, though improvement in performance remained. Another recent paper connected that idea to how people respond to uncertainty and threats. A team of German and Greek researchers completed a nine-month longitudinal study, published in the journal Science Advances, that showed some forms of training changed structures in the cortex and reduced secretions of the stress hormone cortisol.

Military training is partly designed to hold fear in check when carrying out missions that risk death and injury, as well as in the case of disaster. Dave Henson's training before he deployed to Afghanistan helped him to stay composed while detecting and disarming improvised explosives. Then, a year into his tour, Mr. Henson stepped on an IED. He lost both of his legs.

Once the immediate shock of the blast receded, he found himself reciting the process that he had been trained to follow in the event of a casualty scenario. "The training definitely kicked in," he says; it distracted him from the pain. Over the years that followed, Mr. Henson demonstrated another form of bravery, the kind necessary to recover from great trauma and adjust to a new career and way of life. Running on prosthetic limbs, he won a bronze medal in the 200 meters in the 2016 Paralympics in Rio de Janeiro.

Fear can be useful and plays a key role in our self-preservation. We don't want to make people irrationally brave. But fear can be disabling too, in a variety of situations, and overcoming it often allows people to live fuller lives. The new science of bravery holds out the promise of finding that balance, between anxious passivity and recklessness, in our everyday lives.

- Dr. Hooper is managing editor of New Scientist magazine. This essay is adapted from his book "Superhuman: Life at the Extremes of Our Capacity," published last month by Simon & Schuster.

→ This Essay was last updated 20 Oct 2018 14:15 PDT ←