Attempts to Understand Fear and Extinguish Fear Memories

Fear is an important survival mechanism that allows individuals to avoid dangerous and harmful stimuli. However, fear can become debilitating and interfere with one’s ability to function daily within society. Therefore, researchers have begun making attempts to reduce or eliminate the effects of debilitating fearful memories. Before this can be done, a few concepts need be understood. Such concepts consist of what fear actually, is and how researchers are able to distinguish fear from other neurological mechanisms like panic and anxiety.

Dr. Jennifer N. Perusini and Dr. Michael S. Fanselow have made strides in defining fear and distinguishing it from panic and anxiety within their article, “Neurobehavioral perspectives on the distinction between fear and anxiety.” The researchers hypothesized that if there is a distinction between fear and anxiety, then they will feature different antecedent conditions as well as have unique consequences and circuitry. It was noted within this article that this research is necessary because most individuals and the Diagnostic and Statistical Manual of Mental Health Disorders fail to have a clear distinction between anxiety and fear. Furthermore, their definitions are often unclear and tend to define one concept in terms of another. In order to build a more accurate definition of fear and anxiety as well as gain a better understanding of the circuitry involved, the researchers utilized several neurobiological models. These tests were predominantly performed on rats and involved the use of aversive stimuli in order to condition the rats. Unfortunately, the majority of these models failed to consistently distinguish between fear and anxiety. Essentially, all of these tests failed to produce responses that clearly illustrated that fear and anxiety were unique. However, the predatory imminence model was in fact able to distinguish between fear and anxiety. Pre-encounter features strong activity in the pre-frontal cortex. The researchers defined this activity as anxiety. Post-encounter activity in the subcortical forebrain was defined as fear. Lastly, dorsolateral PAG activity was defined as panic. Therefore, the work of Dr. Jennifer N. Perusini and Dr. Michael S. Fanselow successfully distinguished between fear, anxiety, and panic since they identified different antecedent conditions and unique circuitry for fear panic and anxiety.

Researchers at the University of Queensland utilized what they know about fear and its circuitry in order to conduct research on how fearful memories can be extinguished. Specifically, there work was aimed at assisting those with crippling fear. Fear responses differ by species. In Dr. Fanselow’s article, fear in rodents was defined by a freezing behavior. For humans, a fear response could feature impaired cognitive function, inability to perform daily or routine responses, or potentially freezing. In the article from Science Daily titled, “Extinguishing fear memories relies on an unusual change to DNA” the researchers attempted to create new non-fearful memories in similar environments to condition participants and balance the effects of their memories. As a result, the participant would still have the fearful memory so they can exhibit avoidance to certain stimuli, however they will have better responses. To further support the findings, Dr. Xiang Li discovered that the DNA base adenosine is able to be chemically tagged. He also found that fear extinction memories form due to a modification of adenine. Therefore, after performing fear eliciting activities and fear extinction memories, Dr. Li analyzed the adenine bases of the rats and found that fear extinction activities produced these adenine modifications. He also performed an experiment where he prevented these modifications from occurring. Doing so resulted in no fear extinction.

Thanks to Dr. Fanselow and the researchers at the University of Queensland, we now have a better understanding of fear and anxiety, their circuits, and how to manage debilitating fear memories. Hopefully the work of these researchers can pave the way to assisting those with neurological diseases such as Post Traumatic Stress Disorder.

“Extinguishing Fear Memories Relies on an Unusual Change to DNA.” ScienceDaily, ScienceDaily, 20 Feb. 2019, www.sciencedaily.com/releases/2019/02/190220103333.htm.

Perusini, Jennifer N, and Michael S Fanselow. “Neurobehavioral Perspectives on the Distinction between Fear and Anxiety.” Learning & Memory (Cold Spring Harbor, N.Y.), Cold Spring Harbor Laboratory Press, 18 Aug. 2015, www.ncbi.nlm.nih.gov/pmc/articles/PMC4561408/.