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The Removal of Fear From the Brain

By: Sai Srihaas Potu

Fear may be as old as life on Earth. It is a fundamental, deeply wired reaction, evolved over the history of biology, to protect organisms against a perceived threat to their integrity or existence. Fear may be as simple as a cringe of an antenna in a snail that is touched, or as complex as anxiety in a human. Fear is a chain reaction in the brain that starts with a stressful stimulus and ends with the release of chemicals that cause a racing heart, fast breathing, and energized muscles, among other things, also known as the fight-or-flight response.


The fear reaction starts in the brain and spreads through the body to make adjustments for the best defense or flight reaction. The fear response starts in a region of the brain called the amygdala. This almond-shaped set of nuclei in the temporal lobe of the brain is dedicated to detecting the emotional salience of the stimuli.


A part of the brain called the hippocampus is closely connected with the amygdala. The hippocampus and prefrontal cortex help the brain interpret the perceived threat. They are involved in a higher-level processing of context, which helps a person know whether a perceived threat is real.


While fear can play tricks with your memory and your perception of reality, it also affects your body. Fear can weaken the creation of long-term memories and damage the hippocampus, short-circuiting the response paths and causing constant feelings of anxiety. Fear can also have long-term consequences on our health, including fatigue, chronic depression, accelerated aging, and even premature death.


According to recent research, by manipulating the brain activity of a group of participants, the scientists were able to first create and then erase a conditioned fear response, without their subjects even being aware of what was happening.


In the study, the researchers showed subjects a neutral picture and simultaneously administered an electric shock. In this way, the picture came to elicit fear in the subjects which meant a fear memory had been formed. To activate this fear memory, the picture was then shown without any accompanying shock. For one experimental group, the reconsolidation process was disrupted with the aid of repeated presentations of the picture. For a control group, the reconsolidation process was allowed to complete before the subjects were shown the same repeated presentations of the picture.


In that, the experimental group was not allowed to reconsolidate the fear memory, the fear they previously associated with the picture dissipated. In other words, by disrupting the reconsolidation process, the memory was rendered neutral and no longer incited fear. At the same time, using an MRI-scanner, the researchers were able to show that the traces of that memory also disappeared from the part of the brain that normally stores fearful memories, the nuclear group of the amygdala in the temporal lobe.


Subsequently, the deletion of cannabinoid receptor type 1 (CB1) results in a loss of ability to regulate fear. CB1 receptors are found primarily in the brain, to be specific in the basal ganglia and the limbic system, including the hippocampus. They are also found in the cerebellum and both male and female reproductive systems. Cannabinoids are a class of diverse chemical compounds that activate cannabinoid receptors. These include the endocannabinoids (produced naturally in the body by humans and animals), the phytocannabinoids (found in cannabis and some other plants), and synthetic cannabinoids (produced chemically by humans).


All fun aside, abnormal levels of fear and anxiety can lead to significant distress and dysfunction and limit a person’s ability for success and joy of life. Nearly one in four people experience a form of anxiety disorder during their lives, and nearly 8 percent experience post-traumatic stress disorder (PTSD).


Disorders of anxiety and fear include phobias, social phobia, generalized anxiety disorder, separation anxiety, PTSD, and obsessive-compulsive disorder. These conditions usually begin at a young age, and without appropriate treatment can become chronic and debilitating and affect a person’s life trajectory.


Fear is a notoriously difficult emotion to overcome, but a team of researchers may have just invented the perfect shortcut to conquer fear without ever having to face it. Further research has the chance to change the scope of psychology. To this day, many people suffer from fear-related disorders such as PTSD. Current treatment for these disorders lasts multiple years whereas this new treatment can be quicker and much more reliable. Understanding the physiological patterns behind fear can help researchers solve this puzzle and save time and lives as well.



References:

1. Adhikari A, Lerner TN, Finkelstein J, Pak S, Jennings JH, Davidson TJ, Ferenczi E. Biomedical amygdala mediates top-down control of anxiety and fear. Nature. 2015.

2. Åhs F, Kragel PA, Zielinski DJ, Brady R, LaBar KS. Medial prefrontal pathways for the contextual regulation of extinguished fear in humans. NeuroImage. 2015.

3. Amano T, Unal CT, Paré D. Synaptic correlates of fear extinction in the amygdala. Nature Neuroscience. 2010.

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