Justin Feinstein struggled for six years to scare the subject, codenamed SM. He showed her Blair Witch, Fear of Spiders, The Shining, and The Silence of the Lambs - no use.
He took her to an exotic animal store, but for no apparent reason she took the snake out of the terrarium and enthusiastically touched her tongue with her finger. And only because of the intervention of the seller, she could not make friends with the cute tarantula.
Then Mr. Feinstein took her to the abandoned Waverly Hills TB Sanitarium - “the scariest house in the world,” according to the flyers. The attendants of the attraction regularly turned on strange noises and eerie music, and the actors did their best to portray murderers, monsters and ghosts, but she only laughed when other tourists screamed gratefully in horror. Moreover, she accidentally managed to scare one of the "monsters" when she, out of curiosity, tried to touch his head.
Mr. Feinstein, a clinical neuropsychologist at the California Institute of Technology (USA), used this example to understand how fear is born in our brains. The benefits of this are the sea. For example, effective treatments for post-traumatic stress disorder could be developed.
SM came to the attention of scientists when she knocked on the lab of neurologist Daniel Tranel of the University of Iowa (USA) in the mid-1980s. She has just been diagnosed with Urbach-Vite disease. This genetic disorder is so rare that fewer than three hundred cases are known today. Symptoms include skin lesions and calcium deposits in the brain. In SM, the disease destroyed both amygdala.
"Such a localized lesion is extremely rare," says neuroscientist Daniel Kennedy of Indiana University (USA). "There are only a couple of dozen such cases." Seeing this, Mr. Tranel knew he had a unique chance to study the function of this area of the brain.
The amygdala (one in each hemisphere) plays an important role in the formation of emotions, especially fear. This has long been known, but the details are vague. In particular, scientists cannot yet say how much amygdala is necessary for fear, notes Mike Koenigs of the University of Wisconsin in Madison (USA). Perhaps the activity of the amygdala, recorded by the tomograph, is just the result of the activity of other areas of the brain.
It would seem that the case of SM ruled out this possibility, because together with the amygdala, her feeling of fear completely disappeared, while the rest of the emotional palette did not undergo any changes. At the same time, she was distinguished by extreme liveliness. We can say that in a sense she was chasing new sensations. One day, scientists invited her to a restaurant, where she happily chatted with a waiter, and the next day asked to take her to the same place. Seeing the same waiter, she noticeably cheered up and was extremely friendly with him.
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This is a sign that, unlike most other people, SM is unable to recognize subtle cues that make us behave more reservedly in certain situations. “People who you and I would appear to be dark people, she would call trustworthy,” says Mr. Kennedy. "She is biased towards people in the sense that she wants to get closer to everyone." Apparently, the amygdala is responsible not only for fear as an emotion, but also for some aspects of social behavior.
Mr. Kennedy recently tested SM's openness with her sense of personal space. He asked the women to slowly approach SM, and she had to give a signal when she began to feel discomfort. This border is located at a distance of 0.34 m from it, that is, almost twice as close as that of other participants in the experiment.
Moreover, it turned out that SM is not able to read facial expressions, but is not capable of selectively: she sees joy and sadness, but cannot identify fear. Moreover, this is a subconscious reaction: faces distorted by fear or anger, mixed with expressionless faces, appeared on the screen for only 40 ms, and SM was required to press the button as quickly as possible at the sight of a face that expressed fear rather than anger. She coped with this task in about the same way as the others. But when she was given unlimited time to think, she became mistaken.
Digging deeper, Mr. Kennedy discovered that the problem was how her brain directed her gaze. SM just doesn't look people in the eyes when fear is read in them, that is, when they expand. When she was placed in such conditions that she could not help but look into the eyes, she began to more often correctly identify the faces of frightened people.
Thus, the amygdala is not just a "hazard detector". The danger appears to be registered by other areas of the brain, and the amygdala, as a result of this work, directs our attention to gather critical information about the degree of danger. The result is a feeling of dread. And since SM had no amygdala, she felt only excitement akin to excitement, but not fear. This explains why in the pet store and in the "haunted house" she was not indifferent, as one would expect from a fearless person.
But Mr. Feinstein took a break from this coherent theory. He finally managed to scare the poor thing.
In one experiment, she was joined by twins AM and BG with identical injuries to the amygdala. Mr. Feinstein turned to the classic panic test: he asked participants to wear masks that were supplied with air containing 35 percent carbon dioxide. Most healthy people immediately develop shortness of breath, palpitations, sweat, dizzy. About a quarter of them panic.
Oddly enough, all three also experienced panic. SM waved her hands at the mask and shouted, "Help!" When the mask was removed, she said, "I panicked because the hell didn't understand what was going on." For the first time since the onset of her illness, she experienced fear.
The other two reacted in much the same way. AM grimaced and clenched her left hand into a fist, trying to free herself. According to her, she was afraid that she would suffocate, and noticed that this was the most terrible moment in her life. BG began to gasp for air and tore off the mask herself, later admitting that she felt something completely new - the fear of imminent death.
After this, Mr. Feinstein did not know what to think. For decades, the amygdala pair of the brain has been described as the center of fear, and it seemed natural that in their absence, a person would become desperately brave.
However, the scientist soon came to the conclusion that the old theory was not so wrong. Apparently, the brain processes threats from the inside differently (asthma, heart attack, etc.). “This is the primary layer, the basic form of fear,” emphasizes Mr. Feinstein. Indeed, there is nothing to strain attention and assess the state of the environment: a high level of carbon dioxide in the inhaled air directly leads to a change in the acidity of the blood, which triggers a cascade of reactions in the brain. Therefore, panic arises without the "tonsils" - most likely somewhere in the hypothalamus and periaqueductal (central) gray matter.
And here we must pay attention to such an important point. People with amygdala understand that this is a scientific experiment, that scientists will not allow something terrible to happen. That is why their panic is different. In this case, our trio experienced the most real dying horror. They could not properly interpret the excitement that gripped them.
The role of the amygdala in risk assessment explains another bizarre result of these experiments. Healthy participants usually have a pre-emptive reaction when repeating the test: before re-putting on the mask, they change their sweat patterns and have a slightly increased heart rate. Volunteers with Urbach's disease - Vite for the second time behave as fearlessly as the first. Consequently, the amygdala is also responsible for preserving memories of the horror experienced.
Interestingly, in a sample of 200 Vietnam War veterans with traumatic brain injury, none of the patients with damaged tonsils developed PTSD.
So work with this area of the brain should be very careful. On the one hand, because of her, we cannot get rid of painful memories, on the other hand, she protects us and teaches us to avoid dangers in the future. Deprived of her, SM once confessed, "I wouldn't wish that on anyone."