“Memories warm you up from the inside. But they also tear you apart.” Haruki Murakami
We all know from popular drama (TV shows, movies, etc.) that traumatic events are often forgotten by the sufferer. People who experience a devastating event such as a car accident, natural disaster, or terror attack often cannot remember the incident. It’s also common not to remember what took place right before or right after the incident. In a similar way, many adults who suffered child abuse have difficulty recalling large chunks of time from childhood. In these cases, problems with memory can continue into adulthood as well, particularly when faced with emotional distress.
Our brain and nervous system have evolved to do spectacular things: we can read, write, make music, and contemplate the meaning of life. But the brain’s first and foremost duty is to keep us alive. When it comes to traumatic events, the part of our brain that protects our physical and emotional well-being takes control. In this process, the parts of the brain that are responsible for higher thought processes, such as forming and retrieving memories, are suppressed.
How the Brain Forms Memories
On a regular stress-free day, memories for facts are made and stored in three steps: acquisition, consolidation, and retrieval.
- Acquisition occurs through the combination of sensory experience and emotion. The amygdala processes and interprets the experience so it can become a memory.
- The hippocampus consolidates the experience and sends the information off to the appropriate place for storage (memories are stored all over the brain).
- It is thought that retrieval of factual memories occurs as a function of the prefrontal cortex. When we want to think of a fact, such as the definition of a word, the prefrontal cortex retrieves it and we remember.
When we are confronted with life-threatening danger, the brain behaves differently. The amygdala sends an emergency signal to the hypothalamus, which in turn activates the fight or flight response. Corticosteroids are then released into the bloodstream in order to prepare the body for action. Blood pressure, heart rate, and respiratory function all increase to provide the body and brain with extra energy and oxygen. Our alertness increases, and our body is ready to move.
When this is happening, the amygdala inhibits the activity of the prefrontal cortex. When faced with danger, this is useful, as the prefrontal cortex operates substantially slower. While it is trying to work out what is happening, our body may be harmed. The quicker, action-oriented part of the brain enables us to respond rapidly and try to avoid danger. We act fast. Later, once we are safe, we have time to think. In respect to memory, the parts of the brain involved in memory formation are shut down when faced with a traumatic experience.
The activation of the fight or flight response prevents the parts of the brain responsible for creating and retrieving memory from functioning effectively. This is why we can forget what occurred around a traumatic event. In the case of ongoing trauma, such as with childhood abuse, ongoing problems with memory and the related process can occur, leading to what is understood as dissociation.
Dissociation and Memories
At the heart of dissociation is memory disruption.At the heart of dissociation is memory disruption. During dissociation, the normally integrated functions of perception, experience, identity, and consciousness are disrupted and do not thread together to form a cohesive sense of self. People with dissociation often experience a sense that things are not real; they can feel disconnected from themselves and the world around them. Their sense of identity can shift, their memories can turn off, and the connection between past and present events can be disrupted.
In understanding the human response to trauma, it is understood that dissociation is a central defense mechanism because it provides a kind of mental escape when physical escape is not possible. This type of defense is often the only kind available for children living in abusive situations. Posttraumatic stress (PTSD) and complex posttraumatic stress (C-PTSD) often go hand in hand with dissociation. In studies investigating the impact of PTSD and memory, researchers have found that people with dissociative symptoms have a greater impairment with both working memory and long-term memory.
Long-Term Impact of Memory Impairment
To understand the long-term impact of memory impairment due to dissociation, we need to look at the context from which it arises. Dissociation occurs as a result of ongoing trauma which is associated with chronic stress. A chronically stressed brain and nervous system have difficulty learning. The hippocampus, critical for memory formation and consolidation, can become damaged from ongoing exposure to stress hormones. Researchers have found that the hippocampus actually shrinks in people who suffer from major depression. In addition to the emotional impact of chronic stress and abuse, difficulties with learning and memory can occur as well.
Implications range from difficulties with academics to reduced on-the-job learning and performance. In terms of survival, the implications are serious, as we all need the ability to prepare for, find, and keep employment. Unfortunately, once a person frees him or herself from an abusive childhood, the effects can follow into adulthood in unexpected ways. A damaged hippocampus and overactive nervous system can make life more difficult than it has to be. Over time, self-esteem and confidence can be negatively impacted as well.
Fortunately, the prognosis of dissociation can be optimistic. Researchers have found treatment with antidepressants can increase hippocampal volume. Talk therapy and other therapeutic approaches that are designed to reduce stress and increase emotional resilience may also help.
If you are experiencing trauma or dissociation, you can find a mental health professional here.
References
- Bedard-Gilligan, M., & Zoellner, L. A. (2012). Dissociation and memory fragmentation in post-traumatic stress disorder: An evaluation of the dissociative encoding hypothesis. Memory, 20(3), 277-299. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/22348400
- Lanius, R. A. (2015). Trauma-related dissociation and altered states of consciousness: A call for clinical, treatment, and neuroscience research. European Journal of Psychotraumatology, 6(1), 27905. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4439425
- Nuwer, R. (2013, August 1) Why can’t accident victims remember what happened to them? Smithsonian. Retrieved from https://www.smithsonianmag.com/smart-news/why-cant-accident-victims-remember-what-happened-to-them-21942918
- Özdemir, O., Özdemir, P. G., Boysan, M., & Yilmaz, E. (2015). The relationships between dissociation, attention, and memory dysfunction. Nöro Psikiyatri Arşivi, 52(1), 36-41. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5352997
- Phelps, E. A. (2004). Human emotion and memory: Interactions of the amygdala and hippocampal complex. Current Opinion in Neurobiology, 14(2), 198-202. Retrieved from https://www.ncbi.nlm.nih.gov/pubmed/15082325
- Rosack, J. (2003, September 5) Antidepressants may prevent hippocampus from shrinking. Psychiatric News. Retrieved from https://psychnews.psychiatryonline.org/doi/full/10.1176/pn.38.17.0024
- Sapolsky, R. M. (2001). Depression, antidepressants, and the shrinking hippocampus. Proceedings of the National Academy of Sciences, 98(22), 12320-12322. Retrieved from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC60045
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