The Science Behind the Most Perplexing Emotion: Fear

Have you ever heard a strange noise when you were walking down the street late at night? If the answer is yes, how did you feel at that moment? How do you react when you're watching a scary movie and a jumpscare pops up? Whatever your answers to these two questions were, they most likely had something to do with the concept of fear. Fear is such an intriguing emotion for so many reasons. Its presence is both a blessing and a curse simultaneously. It makes us feel uncomfortable but has also benefited us in so many ways. For example, throughout history, humans have utilized fear in order to sense danger and escape from larger animals. This trait has aided the evolution of our species through natural selection because running away from larger creatures means longer life-spans and more opportunities to reproduce. Now, let's dive into the topic of how the human brain interprets the amazing emotion that is fear. 

A Diagram of The Human Brain. The location of the Amygdala is indicated. Source

The amygdala and more specifically the basolateral amygdala are regions of the brain that take in the majority of the sensory inputs that are related to fear associations. The basolateral amygdala is made up of the lateral, basal, and accessory-basal nuclei of the amygdala. The lateral nuclei takes in most of the sensory information. This information comes to the lateral nuclei from the temporal lobe structures of the brain (the hippocampus and the primary auditory cortex). This same information is then interpreted by the basolateral complex. Then, it's shipped to the central nucleus of the amygdala which further processes the information. The process I just described encapsulates the cerebral system that mammals (including humans) use to express emotions. Now that we have a broad understanding of the basolateral amygdala and its function, let's get back to talking about fear. 

The central nucleus of the amygdala is commonly thought of as the main source for moderating fear responses. These responses are dealt with by specific regions and subdivisions of the central nucleus itself. The amygdala's broader purpose is understanding and interpreting the emotional significance of the stimuli (in other words, to what level does something affect us). The amygdala comes to life when one sees a face filled with emotion. In the wild, the sight of a predator causes a fear response within the amygdala of a prey. This response prepares parts of the brain having to do with motor responses (the movement of our muscles) so that the prey can escape the danger it's in by running/flying away. Certain threats also cause the secretion of stress hormones which leads to changes within our bodies that keep humans alert (pupils dilate, breathing gets quicker, etc.). 

This Diagram of the Brain Indicates the Location of the Hippocampus. It's very close to the amygdala. Source

The hippocampus is a region of the brain that is heavily associated with the amygdala. The hippocampus along with the prefrontal cortex allow the brain to process different dangers/threats in a specific manner. They interpret threats in a very complex way that allows a person to understand if something that's thought to be dangerous is actually dangerous (supposed danger vs. actual danger). The structures of the brain mentioned in this paragraph are what allow us to feel safe in various situations such as when we're at the zoo and we see lions and tigers in man-made habitats. Thanks to our brains, we don't feel as if the animals can hurt us because our hippocampus and frontal cortex tell us that the animals are contained. The hippocampus and the frontal cortex cause the fear response of the amygdala to be reduced significantly in situations like this. Now, allow me to introduce you to one of the bravest and most incredible human beings on this Earth. Please trust me when I say that I'm not about to go completely off topic!

World Famous Professional Rock Climber Alex Honnold "Free-Soloing" El Capitan in Yosemite National Park. Source

Alex Honnold isn't your typical rock climber. He's a complete and utter daredevil who puts his life on the line on a consistent basis for his craft. Honnold is famous for his "free solo" climbs of massive walls that occur in nature. Free soloing is only meant for the boldest of the bold. This method of climbing includes ascending massive walls without the use of cables, ropes, harnesses, or any safety equipment. If you're free soloing a massive stone wall and you fall, it's all over. This is why the vast majority of people on this planet don't free-solo! Only a very small group partakes in this activity and Honnold is a part of it. Free-soloers like Honnold must depend fully on their preparation, physical prowess, and technical skills in order to preserve their lives. The movie "Free Solo" documents Alex Honnold's shocking free solo climb of El Capitan, which is considered by many to be the hardest climb possible on Earth. Here's where we connect all of this to the brain and the idea of fear. You might be wondering, "how does Honnold stay calm enough to perform such daunting tasks? Is he scared out of his mind when he's sandwiched between a 4x4 inch crack of granite thousands of feet above the ground?" The answers to these questions may surprise you. Honnold's brain is a complete anomaly. 

Alex Honnold getting an MRI to calculate his brain's fear levels. Source

One time, Alex Honnold was doing a presentation at Explorers Hall which is part of National Geographic's HQ. After blowing the minds of all in attendance with pictures and stories about his greatest climbs, Honnold was approached by a neurobiologist who said to one of his friends, "That kid's amygdala isn't firing." In March 2016, Honnold received an MRI at the Medical University of South Carolina in Charleston. The machine that scanned him is basically a massive magnet that pinpoints activity in all the regions of the brain through mapping blood flow. Honnold's reaction to this neurobiologist's curiosity was pretty hilarious. He kept saying stuff like "I feel totally normal, whatever that means." I think anyone would be uncomfortable if a medical professional told them they were essentially wired differently than most of the human population. The neuroscientist who performed the scan of Honnold's brain is named Jane Joseph. Joseph was among the first group of scientists to do MRIs on "high sensation seekers": those who seek out thrilling experiences and assume large risks to do so. Joseph considered Honnold to be on a different level than these sensation seekers. Honnold is what she calls a "super sensation seeker": someone who seeks the greatest of dangers who is also capable of strictly controlling the brain and body's reaction to these dangers. Joseph's plan was to check on his amygdala after the scan to see if Honnold actually didn't have any fear. After the scan, Joseph and her colleagues noticed that Honnold does indeed have a working, healthy amygdala. The next discovery they made was shocking. 

Honnold's Brain (left) vs. a control subject's brain (right). The control is a climber in Honnold's age range. The amygdala is located at the intersection of both crosshairs. The glowing colors indicate activity. Source

During the brain scan, Honnold had been shown gruesome images of all sorts in order to stimulate activity in his amygdala. The control subject was shown the same images. The pictures above show the activity in Honnold's brain (left) and the control's brain (right) after seeing the gruesome images. The intersection of the crosshairs indicates the location of the amygdala and neon color indicates activity. Honnold's amygdala is literally silent. This is so fascinating to me. He basically had zero fear response to seeing very violent and disturbing videos and images. The control's amygdala was very active after seeing the images as shown by the picture on the right. After playing a risk and reward game that monitored amygdala activity, Joseph noticed the same results as she'd seen after Honnold and the control subject saw the gruesome images in the first experiment. Joseph described Honnold's brain as lifeless to which Honnold jokingly replied, "There's just not much going on in my brain. It just doesn't do anything." Now, you might be wondering, does Honnold's brain respond in the same way when he free-solos gargantuan rock walls? Yep! This is precisely what Joseph thinks is happening. Since there's zero activation of his amygdala, there's most likely zero threat response, she says. What a crazy conclusion to this experiment. Honnold is potentially BIOLOGICALLY fearless. It's almost too crazy to believe!

Hopefully, after reading this article, you have a whole new outlook on what fear really is. Would you prefer to be literally fearless and a massive risk-taker like Alex Honnold? Or would you rather just stay the way you probably already are: fearful and more measured? Let me know in the comments and thanks for reading!