Memory and trauma

Memory is described by psychology as the ability of an organism to store, retain, and subsequently retrieve information. When an individual experiences a traumatic event, whether physically or psychologically traumatic, his or her memory can be affected in many ways. For example, trauma might affect his or her memory for that event, memory of previous or subsequent events, or thoughts in general.

Physical trauma

When people experience physical trauma, such as a head injury in a car accident, this can have effects on their memory. The most common form of memory disturbance in cases of severe injuries or perceived physical distress due to a traumatic event is post-traumatic stress disorder,^[1] discussed in depth later in the article.

Brain damage

Damage to different areas of the brain can have varied effects on memory. The temporal lobes, on the sides of the brain, contain the hippocampus and amygdala, and therefore have a lot to do with memory transition and formation. Patients who have had injury to this area have experienced problems creating new long-term memories. For example, the most studied individual in the history of brain research, HM, retained his previously stored long-term memory as well as functional short-term memory, but was unable to remember anything after it was out of his short-term memory.^[2] A patient whose fornix was damaged bilaterally suffered severe anterograde amnesia but no effect on any other forms of memory or cognition.^[3] In the fictional case of a patient with a cherry-sized tumor pressing on the temporal lobe of his brain, he temporarily suffered total retrograde amnesia, even after surgery was performed to remove the tumor.^[4] However, with time, he was not only able to remember everything starting after the surgery, but childhood memories, up to age 12, all returned with clarity.

Psychological trauma

Relevant memory

Of the different aspects of memory – working, short-term, long-term, etc – the one most commonly affected by psychological trauma is long-term memory.^[5] Missing memories, changes to memory, intensified memories – all are cases of manipulations of long-term memory.

Physical aspect

Long-term memory is associated with many different areas of the brain including the hippocampus, amygdala, thalamus and hypothalamus, peripheral cortex and temporal cortex. The hippocampus and amygdala have been connected with transference of memory from short-term memory to long-term memory.^[6] Thalamus and hypothalamus, located in the forebrain, are part of the limbic system; they are responsible for regulating different hormones and emotional and physical reactions to situations, including emotional stress or trauma. The thalamus is also related to reception of information and transferring the information, in the case of memories, to the cerebral cortex.

Physical effects

Psychological trauma has great effects on physical aspects of patients’ brains, to the point that it can have detrimental effects akin to actual physical brain damage. The hippocampus, as mentioned above, is involved in the transference of short-term memories to long-term memories and it is especially sensitive to stress. Stress causes glucocorticoids (GCs), adrenal hormones, to be secreted and sustained exposure to these hormones can cause neural degeneration. The hippocampus is a principal target site for GCs and therefore experiences a severity of neuronal damage that other areas of the brain do not.^[7] In severe trauma patients, especially those with post-traumatic stress disorder, the medial prefrontal cortex is volumetrically smaller in size than normal and is hyporesponsive when performing cognitive tasks, which could be a cause of involuntary recollection (intrusive thoughts)^[8]. The medial prefrontal cortex controls emotional responsiveness and conditioned fear responses to fear-inducing stimuli by interacting with the amygdala. In those cases, the metabolism in some parts of the medial prefrontal cortex didn’t activate as they were supposed to when compared to those of a healthy subject.

Psychological effects

As with many areas of psychology, most of these effects are under constant review, trial, and dissent within the scientific world regarding the validity of each topic.

Repressed memory

Main article: Repressed memory

Perhaps one of the most controversial and well-known of the psychological effects trauma can have on patients is repressed memory. The theory/reality of repressed memory is the idea that an event is so traumatic, that the memory was not forgotten in the traditional sense, or kept secret in shame or fear, but removed from the conscious mind, still present in the long-term memory but hidden from the patient's knowledge.^[9] Sigmund Freud originated the concept of repression and it has developed and changed since his original work.^[10] In the eyes of critics of repressed memory, it is synonymous with false memory; however its proponents will argue that these people truly did have traumatic experiences.

Intrusive thoughts

Main article: Intrusive thoughts

Intrusive thoughts are defined as unwelcome, involuntary thoughts, images or unpleasant ideas that may become obsessions, are upsetting or distressing, and can be difficult to be free of and manage. In patients who have suffered from traumatic events, especially those with post-traumatic stress disorder, depression or obsessive-compulsive disorder, the thoughts are not as easy to ignore and can become troubling and severe. These thoughts are not typically acted on; the obsession of the thoughts usually comes from intense guilt, shame or anxiety relating to the fact that the patient is having the thoughts to begin with so they are unlikely to actually act on things they feel so badly about. In trauma patients, the intrusive thoughts are typically memories from traumatic experiences that come at unexpected and unwanted times. The primary difference from other intrusive thoughts sufferers is that the memories are real rather than imagined.

Emotion

Emotion is a large part of trauma, especially near death experiences. The effect emotions have on memory in different instances is an integral part of the effect of trauma on memory. Emotional events tend to be recalled with more frequency and clarity than memories not associated with extreme emotions^[11]. Typically traumatic events, such as physical attack or sexual abuse, are interrelated with strong negative emotions, causing these memories to be very strong and more easily recalled than memories not associated with similar emotions, or even those connected to positive emotions. Emotion's strong connection with memory also has to do with how much attention or focus an individual has on the event. If they are heavily emotionally involved in the event, a lot of their attention is directed at what’s happening, rendering it a stronger memory. It is also the case with emotionally aroused situations that even if attention is limited, it is more likely that a memory associated with the strong emotion will remain as opposed to some neutral stimulus. Chemically, this is because the emotional and physical stress caused by traumatic events creates an almost identical stimulation in the brain to the physiological condition that heightens memory retention. It excites the neuron-chemical activity centers of the brain that affects memory encoding and recollection.^[12] This reaction has been enforced by evolution as learning from high-stress environments is necessary in "fight or flight" decisions that characterize human survival.

Post-traumatic stress disorder

Main article: Posttraumatic stress disorder

PTSD is an anxiety disorder caused by exposure to a terrifying event or ordeal involving the occurrence or threat of physical harm. It is one of the most severe and well-known of the different types of psychological trauma, mostly due to it’s prevalence in war veterans. As mentioned above, the stress of PTSD can have severe effects on the hippocampus, causing problems with transferring short-term to long-term memory. There is no one way that patients’ memories are affected by PTSD, as shown by a variety of studies.^[13] Typically symptoms include avoidance of reminders of the traumatic event or mention thereof, irritability, trouble sleeping, emotional numbness and exaggerated reactions to surprises. One of the most common and powerful symptoms, is the recurrence of random intense memories from the event (intrusive thoughts). This can manifest itself in different ways such as flashbacks of the event and unwanted thoughts about the trauma (e.g. “why did this happen to me?”).^[14] PTSD patients who have gone through different traumatic experiences will have small variances in their symptoms, mostly insignificant. For example, PTSD patients who were rape victims will have aversion to words such as touch and dirty while patients who were in a fire or war experience will respond similarly to words like burn or fight.^[14]

Therapy

For patients who have suffered physical trauma that led to their memory damage, surgery can sometimes get them back to normal. Sometimes, as in the case of the patient mentioned above who had a tumor that caused his memory loss, therapy is needed to help recover memories. Drug therapy is more common in cases where the psychological trauma caused chemical imbalances and other physical changes in the brain which affected memory. Patients who use drug therapy also frequent some type of psychotherapy as well.

See also

• Effects of stress on memory
• Involuntary memory
• Muscle memory

References

1. ^ Davidson, J.R. Trauma: The impact of post-traumatic stress disorder. Journal of Psychopharmacology.2000; 14(2 Suppl. 1):S5–S12.
2. ^ Corkin, S. (2002). What’s new with the amnesic patient H. M.? Nat. Rev. Neurosci. 3: 153-160.
3. ^ Calabrese P, Markowitsch HJ, Harders AG, Scholz M, Gehlen W.(1995). Fornix damage and memory: A case report. (3):555-64. Physiological Psychology, University of Bielefeld
4. ^ Krauss, Nicole. (2002) Man Walks Into A Room. New York: Doubleday
5. ^ Squire, Larry S. (1987) Memory and Brain. New York, New York: Oxford University Press
6. ^ Fuster, Joaquin M. (1995) Memory in the Cerebral Cortex: An Empirical Approach to Neural Networks in the Human and Nonhuman Primate. Cambridge, MA: The MIT Press.
7. ^ Tarara, R., Else, J.G., Suleman, M.A., Sapolsky, R.M. (1989). Hippocampal damage associated with prolonged and fatal stress in primates. J Neurosci 9:1705-1711.
8. ^ McNally, Richard J. (2006) Trends in Cognitive Science, Volume 10, Issue 6: Cognitive Abnormalities in Post Traumatic Stress Disorder. P271-277
9. ^ Loftus, Elizabeth and Ketcham, Katherine. (1994) The Myth of Repressed Memory: False Memories and Allegations of Sexual Abuse. New York, New York: St. Martin’s Press
10. ^ Freud, Sigmund, and Breuer, Josef. (1895). Studies on hysteria
11. ^ L. Cahill, B. Prins, M. Weber and J.L. McGaugh , (1999).4Beta-adrenergic activation and memory for emotional events. Nature 371, pp. 702–704
12. ^ Christianson, S.A., & Loftus, E. (1990). Some characteristics of people's traumatic memories. Bulletin of the Psychonomic Society, 28, 195-198.
13. ^ Brewin, Chris R. (2003) Posttraumatic Stress Disorder: Malady or Myth?. New Haven and London: Yale University Press
14. ^ ^{a b} Loftus, Elizabeth and Ketcham, Katherine. (1994) The Myth of Repressed Memory: False Memories and Allegations of Sexual Abuse. New York, New York: St. Martin's Press