Acquiring and losing our fears: from the general to the specific
(a sketch in bits and pieces)
Fears come in all sorts of flavors. Our brains maintain records of our fearful experiences and they have been registered in memory through a variety of pathways. Some pathways are innate but most are learned. In some instances fear itself can disappear through damage to specific brain regions.
Part 1
No doubt you know all about Pavlov and his dogs that learned to salivate when hearing a bell that was associated with a tasty meat treat. During the following hundred years we have learned all about conditioning, how it works, the brain circuitry involved, how to form associations of all sorts and how to ‘erase’ (extinguish) what was learned. Fear is just one of the classes of our responses to the elements of the world around us and all of us can learn to fear almost anything from fear associated with eating oysters to the sound of a drill sergeant’s voice. While this is all too familiar to you it is nevertheless important to note that many of our fears, the ones that are irrational are perfectly reasonable when we take into account our learning history. We are after all the product of our experiences including our history of learning which need not be intentional. You also of course know that getting rid of an irrational fear through deconditioning is easy to understand but hard to accomplish. Think of what it would take to get someone we know who is afraid of flying, or elevators, or public speaking, or close relationships to give up their fear.
What also helps to amplify our learned fears is the power of our imagination. After all minds are powerful instruments for creating all sorts of realities including what we fear onto death.
Part 2
What would it be like to never experience fear and would you want for yourself? No doubt many of us would consider a treatment that would erase some of our fears, especially the ones that are disabling and irrational but all fears Well that is a nothing all together.
Imagine day traders, soldiers in the battle field, politicians, gamblers, drivers in traffic, football players, without being able to experience fear but unimpaired in other mental functions. Imagine being able to block the functioning of a key brain structure that is essential for experiencing fear. In the laboratory such a phenomenon is within the realm of the possible. Accidents of nature can actually produce fearless humans.
In an ‘old’ study published on the on line journal in Current Biology (Dec. 16, 2010) Justin Feinstein and his colleagues report their observations from a study of a woman who suffers from an unusual genetic disorder called Urbach-Wiethe disease. During early adolescence the disease destroyed both sides of her amygdale and as a result she could not experience, report, being fearful. The researchers explored in detail her life experiences including whether she experienced fear when reaching for poisonous snakes, when in haunted houses (she giggled) and on one occasion she described escaping the clutches of a knife-wielding man. She didn’t run but calmly walked away from him. When the researchers tried to induce a fear response via scary films they could not elicit fear.
Would you want to go through life without fear? I think most of us would prefer being scared some of the time.
Part 3
Being fearful is useful (much of the time). After all we live in a world with potential dangers to our health and well being. Without being fearful we might not survive. It is not only the bump in the night, the surge of wind pushing the ocean towards us, and a test result at the doctor’s office that spells disease are just some obvious fear provoking events. Add to that list all that places, people and things associated with threat to our safety and composure, ‘events that have been associated, tied, to what can frighten us that now are perfectly suited to make us fearful. Fear is a reflex response to a danger signal tied to an event, place, thing, not unlike the odor of a juicy steak on the barbeque, can get your gastric juices going.
However what about irrational fears, fears associated with flying, elevators, public speaking, open or closed spaces, snakes, birds, clowns and you can add your favorites to that list. We can consider how we became saddled with these types of irrational fears that can disrupt our lives and happiness. Most often we can’t come up with a cause an effect. However, for many, people crippled by anxiety, illogical fears, their lives are miserable as a result of these awful emotions that persist without end. No wonder that many forms of treatments have been formulated and tested to alleviate ‘neurotic’ fears.
Much of this research has been completed in people but even more has been tested in animals that have been made fearful in the laboratory. One recent treatment strategy is to ‘fix’ fearful memories through the use of drugs that induce epigenetic changes to DNA. One of the foundations of the study conducted at MIT by Li-Huei Tsai and colleagues (published in the journal Cell, Jan 16, 2014) is the well known fact that recent memories are more amenable to reconsolidation than memories that have been around for a long time. What the MIT researchers showed is that a DNA modification that is controlled in part by the enzyme histone deacetylase 2 (HDAC2) helps make recent (fearful) memories more prone to reconsolidation. They found that HDAC2, which is responsible for removing acetyl groups from histones, is modified by nitrosylation and dissociated from chromatin during recall of early memories, allowing memories to be modified.
Sleep can also be used to cure individuals from irrational fears. In an article that appeared in Nature Neuroscience researchers ( Katherina Hauner and colleagues) demonstrated that training during sleep can diminish fearful memories. First they created a fear in volunteers via mild electric shocks as subjects viewed pictures of faces that were paired with a distinct odor. After confirming that a mild fear was conditioned in association to the faces and odors. The subjects then napped in the laboratory and researchers monitored their brain waves. When the volunteers entered slow-wave sleep the researchers released one of the fear-linked odors in 30-second intervals and that triggered the memory of being shocked (measured by monitoring sweating) but the sweating decreased with repeated exposure to the odor.
When the subjects woke up they showed diminished fear responses when exposed to the odor–face combination that had been triggered repeatedly during sleep. They also noted changes in the activity in the amygdala, a region of the brain involved in emotion and fear. This suggested that the sleep treatment did not erase the fearful memory, but indicated new ‘learning had taken place. The odor no longer was associated with fear of being shocked.
Other studies have also demonstrated that learning can take place during sleep and in this study learning involves unlearning of a conditioned fear response.
Obviously there is so much more to say about what is known about how fears start, are maintained, and sometimes wane and, in time and experience are lost from memory.
Much more later