Welcome to brain Stuff. Production of I Heart Radio, Hey brain Stuff Lauren vogelbam here. Almost a decade ago, scientists introduced the world to patient s M. At first glance, the forty four year old mother of three seemed to lead a pretty average life, but upon closer observation, she exhibited one rare and somewhat troubling characteristic. She had no fear.
Researchers wrote to provoke fear and SM. We exposed her to live steaks and spiders, took her on a tour of a haunted house, and showed her emotionally evocative films. On no occasion did SM exhibit fear, and she never endorsed feeling more than minimal levels of fear. The reason s M had lippoid protein osis or werbak Vita syndrome, a rare condition that damaged an important structure in her
brain called the amygdala. But aside from plowing fearlessly through some of life's unsettling triggers, SM functioned relatively normally, which begs the question can you live without the amygdala? But let's back up a tiny step. What is the amygdala? Located deep within the brain's temporal lobes. It's an almond
shaped massive cells or nuclei. That's your amygdala. It's a bit misleading to think of the structures one single unit, since there are actually two parts to it, each one located in opposite hemispheres of the brain, but for general purposes, the distinct halves are considered as one part of the limbic system, which are the brain structures involved in matters
of emotions and motivations. The amygdala specifically is associated with memory storage and the processing of emotions like anger, pleasure, and yep, you guessed it, fear. One major part of the amygdala's role is its responsibility in fear conditioning, an associative learning process that allows us to learn through repeated experience to be scared of something. That learning process happens because experiences change our brain circuitry and form new memories.
This concept was pretty clearly illustrated in experiment which was totally unethical by today's standards. Involving an eleven month old infant own as a little Albert. Scientists John Watson and Rosalie Rayner wanted to see what would happen if they paired Albert's perfectly natural fear of loud noises with the stimulus he seemed to be pretty neutral about, in this case, a white rat. Watson and Rayner allowed Albert to reach for the rat, and every time he did, they struck
a hammer against a steel bar. After sadden repetitions of this pairing, Albert started bursting into tears at the very sight of the rat. No hammer needed. Because of this fear conditioning, his amygdala had linked the disturbing noise with the neutral stimulus, and the latter now elicited fear without the former. Unfortunately for poor Albert, and again this type
of experiment would not go down today. The experiment led him to develop a generalized fear of things that even resembled the white rat, so white coats and white dogs would freak him out too. But back to Patient s M. On the surface, her fearlessness seems kind of funny, charming. Even her kids even got a kick out of it. Her eldest son once wrote, me and my brothers see the snake on the road. I was like, holy cow,
that's a big steak. While Mom just ran over there and picked it up and brought it out of the street and put it in the grass. And let it go on its way. She would always tell me how she was scared of snakes and stuff like that, but then all of a sudden, she's fearless of them. But while navigating life without anxiety may seem somewhat exciting and patient, SM has made it clear that a person can survive perfectly well without an intact amygdala. The absence of natural
fear can be dangerous, even potentially fatal. A complete lack of suspicion or distrust meant SM was vulnerable in many ways. Once, while walking through a small park at ten PM, a man accosted SM and held a knife to her throat. According to researchers quote, in the distance, she could hear the church choir singing. She looked at the man and confidently replied, if you're going to kill me, you're going
to have to go through my God's angels first. The man suddenly let her go, and if that wasn't strange enough, SM didn't flee the scene. She simply walked home. And she walked past the same park the next day and showed no signs of fear or avoidance. She just didn't have it in her. That wasn't the only time SM walked right into seriously risky situations and emerged unscathed and unbothered.
Researchers say she was once physically accosted by a woman twice her size, she was nearly killed an act of domestic violence, and on more than one occasion, she's been explicitly threatened with death. What stands out most is that in many of these situations, SM's life was in danger, yet her behavior lacked any sense of desperation or urgency.
But while SM has been held up as the prime example of a fearless, amygdala less life, more recent research has indicated that the connection between the two characteristics isn't so clear. According to a study published in the journal Nature Neuroscience, people with damaged amygdala's did still report feelings of intense fear, and some even felt more fear than those with normally functioning amigdala's. The study looked at participants with the same super rare genetic condition that caused SMS
amygdala damage or about vita disease. Less and three hundred people have been found to have it since it was discovered in nine nine. Orbak vita disease causes three main types of symptoms an extremely hoarse voice, small bumps around the eyes, and calcium deposits in the brain. The amygdala happens to be the spot in the brain where these
deposits form. Researchers found that watching horror films did nothing to incite fear in participants with this disorder, but they were curious whether exposing them to carbon dioxide would induce a fear reaction. The amyndella plays a big part in detecting carbon dioxide, and when it detects higher concentrations of it in the blood, a possible sign that suffocation is occurring. It can cause a person to feel panic, contrary to
what seemed logical. When participants with worbok Vita syndrome breathed in air that was thirty five carbon dioxide, they freaked out. So what's the deal, a, researchers wrote. Results indicate that the amygdala is not required for fear and panic and make an important distinction between fear triggered by external threats from the environment versus fear triggered internally by carbon dioxide. So can you live without the amygdala? Yes? Can you
live safely and securely without it? Still unclear what scientists are working to figure it out. Today's episode was written by Michell Konstantinovski and produced by Tyler Clain. Brain Stuff is a production of I Heart Radio's How Stuff Works. For more in this and lots of other brainy topics, visit our home planet, how stuff Works dot com. And for more podcasts for my heart radio, visit thy heart radio app, Apple Podcasts, or wherever you listen to your favorite shows.