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The biology of how the brain forgets

Our brain tends to forget things that we wish we would always remember. And yet, it cannot forget certain things we wish never occurred and existed. How does your brain forget? And, can your brain forget on purpose? By nature, the human brain forgets. Inopportunely, the biological mechanism underlying this brain process is poorly understood. Only few studies shed light on this aspect. In May 2012, scientists attempted to explain the molecular biology of active elimination of memories on their report. In September 2018, another team of researchers identified the parts of the brain associated with forgetting. Based on brain frequencies, they analyzed how the human brain voluntarily forgets.

 

 

 

Molecular biology of forgetting

In 2012, an independent research team from the Scripps Research Department of Neuroscience attempted to understand the molecular biology of active forgetting.1 To do so, they used fruit flies (Drosophila) as key model since this species is often used for studying memory. Accordingly, they found that a small subset of dopamine neurons regulated the acquisition as well as the forgetting of memories. In other words, they saw that the neurons that acquired memory on one hand also eliminated the memory on the other hand. Notably, they identified the two dopamine receptors involved, i.e. dDA1 and DAMB.

 

In this case, dopamine, a neurotransmitter, seemingly performs dual, yet opposing, roles. At first, the dopamine activates the dDA1 receptor of a neuron. In effect, the neuron begins forming memories. However, the same neuron sends out signal via another dopamine receptor, DAMB. As dopamine binds to the DAMB receptor, it activates the receptor. As a result, it triggers events that lead to the forgetting of the recently acquired memory (provided that the memory has not been consolidated yet). A process, called consolidation, protects important memories from being forgotten. In essence, while memory actively forms, a dopamine-based forgetting mechanism works as well. Unless the brain reckoned the memory as important, it erases the forming memory.

 

 

 

Forgetting on purpose

In September 2018, researchers from Ruhr-Universität Bochum and the University Hospital of Gießen and Marburg collaborated with researchers from Bonn, the Netherlands, and the UK.2  In brief, they identified the parts of the brain involved in the process of voluntary forgetting. In particular, these brain areas include the prefrontal cortex and the hippocampus, the brain region associated with memories.

 

In this recent study,  the researchers found that the prefrontal cortex regulates the activity in the hippocampus. One of the leaders of the team, Carina Oehrn, explicated that the prefrontal cortex suppressed hippocampus activity. Further, she noted that the frequency changed. Accordingly, the difference in frequency caused the currently processed information to cease from being encoded. They referred to this frequency as the forgetting frequency.2

 

 

 

Forgetting – crucial to health

biology of forgetting - post-traumatic stress disorder
A Marine attended art therapy to relieve post-traumatic stress disorder painted this mask. Credit: Work by Cpl. Andrew Johnston, and released by the United States Marine Corps.

 

As much as recalling is important, forgetting certain things is pivotal to mental and emotional well being. We inherently forget on purpose. Imagine remembering all – both good and bad. Not only we would have to deal with information overload but we would also be long exposed to feelings associated with those memories.

 

Post-traumatic stress disorder, regarded as a mental disorder, develops when a person has gone through a traumatic event. People with this condition face higher risks of inflicting self-harm, or worse, committing suicide.3 Hyperthymesia, a condition wherein an individual can extraordinarily recall much of one’s life in vivid and perfect detail, can be off-putting and distressing to the affected individual. Based on one such case, the patient recounted how the ability to remember constant, uncontrollable chain of memories could be exhausting and a burden.4

 

 

More research

The metaphorical inability to forget hinders a person to move on and focus on the tasks at hand. Traumatic events seem to be ingrained deeply in mind and soul. For instance, loss of a loved one, warfare, and sexual assaults prove to be difficult to ignore. Thus, we need more insights on the neuro- and molecular biology of forgetting. More studies could help shape up future therapeutic intervention. It may not necessarily lead to the absolute incapacity to recall. But, hopefully, it can help set aside spiteful memories. In that way, affected individuals could be freed from the traps of the past, and help them live life with a sanguine hope for a future.

 

 

 

— written by Maria Victoria Gonzaga

 

 

 

References:
1 Sauter, E. (2012, May 14). “Team Identifies Neurotransmitters that Lead to Forgetting”. The Scripps Research Institute. Retrieved from https://www.scripps.edu/newsandviews/e_20120514/davis.html
2 Ruhr-University Bochum. (2018, September 7). This is how the brain forgets on purpose: Two brain regions apparently play a pivotal role in forgetting. ScienceDaily. Retrieved from www.sciencedaily.com/releases/2018/09/180907110501.htm
3 Bisson, JI; Cosgrove, S; Lewis, C; Robert, NP (2015, November 26). “Post-traumatic stress disorder”. BMJ (Clinical research ed.). 351: h6161. doi:10.1136/bmj.h6161. PMC 4663500
4 Parker ES, Cahill L, McGaugh JL (2006, February). “A case of unusual autobiographical remembering”. Neurocase. 12 (1): 35–49. doi:10.1080/13554790500473680.