Memory and trauma is the deleterious effects that physical or psychological trauma has on memory.
Memory is defined by psychology as the ability of an organism to store, retain, and subsequently retrieve information. When an individual experiences a traumatic event, whether physical or psychological trauma, their memory can be affected in many ways. For example, trauma might affect their memory for that event, memory of previous or subsequent events, or thoughts in general. Additionally, It has been observed that memory records from traumatic events are more fragmented and disorganized than recall from non traumatic events. Comparison between narrative of events directly after a traumatic event versus after treatment indicate memories can be processed and organized and that this change is associated with decrease in anxiety related symptoms.
Physical trauma When people experience physical trauma, such as a head injury in a car accident, it can result in 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, discussed in depth later in the article.
Traumatic brain injury 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. A patient whose fornix was damaged bilaterally developed severe anterograde amnesia but no effect on any other forms of memory or cognition.
Brain trauma In addition to physical damage to the brain as a result of mechanical injury, there are other changes in the brain that can be observed. Neuroimaging studies on PTSD repeatedly identify key structures associated with pathology development. The structures observed to change are the amygdala, Anterior Cingulate Cortex (ACC), Pre Frontal Cortex (PFC), insula, and hippocampus. These parts of the brain are most affected because they contribute to the feeling and actions associated with fear, clear thinking, decision making and memory. As a result of individual changes within different brain structures communication and regulation within structures is also impacted.
Amygdala The Amygdala is known as the "fear center of the brain," and is thought to be activated and regulated in response to stressful situations marked with perceived heightened stimulation. Specifically, the Amygdala is responsible for identifying threats of danger to self and safety. Consistent exposure to trauma and or stress, may lead to over-perception and heighten responsibility and sensitivity to threat. Increased activation in the fear center can impact communication with other circuits in the brain structure including connections between the PFC, amygdala, and hippocampus which can in turn affect how memory are stored by the hippocampus.
A person's amygdala does not fully develop until their late 20s. Stress experienced prior to that age may have more extensive impact compared to stress experienced after the amygdala is fully developed.
Pre-frontal cortex The PFC is a brain structure responsible for executive functioning skills. Included in executive function abilities are emotional regulation, impulse control, mental cognition, and working memory among many other abilities.The PFC is also in charge of modulating response from the Amygdala. However, during high-stress situations, the Amygdala can suppress higher thinking functions of the PFC. Some PFC functions that may be impacted during traumatic stress include; failure of emotion reappraisal, heightened salience of emotional stimuli, failure to inhibit neuro-endocrine response to threat stimuli, inability to maintain or use extinction of conditioned fear.). People who have experienced trauma, especially chronic and ongoing trauma, may be observed to have under-activation of multiple parts of the PFC. Under activation of the PFC can lead to decreased modulation of the amygdala during a stress response. The PFC in most vulnerable to the effects of stress during adolescent and a traumatic event during this time period would have more extensive changes than stress experience when the PFC is fully developed around the mid 20s.
Hippocampus The hippocampus is considered the memory center for the brain and is responsible for storing, encoding, retrieving, and reconsolidating memories. Studies indicate that people who have PTSD may have a "shrunken" hippocampus, some estimates indicate that there may be up to a decrease in a range of 5-26%. However, there are alternative explanations to account for the observed decreased hippocampus volume. One study by Gilbertson et al. (2002), suggests that perhaps decrease hippocampal volume may be a pre-existing factor that may predispose people for the development of PTSD. There are conflicting interpretation in understanding if decreased hippocampal volumes are a consequence or a pre-existing vulnerability associated with PTSD. While it is unclear if decreased hippocampal volume is evident as a consequence or prior to the traumatic event; there are numerous studies that indicate the hippocampus in under active during traumatic events and potentially also under-active after the event as well. An underactive or dysregulated Hippocampus has many clinical implications including in areas of neurogenesis, disturbances to organization of memory, and ability to impact other endocrine functions such as a stress-response.
The hippocampus is a major site of neurogenesis, it is where new neurons are born, impact to neurogenesis can have multiple implications. Some studies suggest that blocking of neurogenesis may have the ability to block the efficacy of anti-depressants which are used to treat symptoms of depression. According to the DSM-5 there is comorbidity among depression and PTSD. In addition to comorbidity rates, the symptoms of PTSD and Major Depression Disorder (MDD) also have some overlap. Specifically, both list negative alteration in mood and cognitive disturbances as a symptom, underlying the idea of a "c" factor or a cognitive dysfunction that can be seen as a transdiagnostic dimension of psychopathology. Trauma can impact the hippocampus and may have global implications in mood and symptom progression through the impacts on neurogenesis.
Changes to the hippocampus also may have impact to a person's ability to recall the traumatic experience and produce a trauma narrative . There have been studies that further expand on how trauma can impact victims ability to recall traumatic events. These memory difficulties in identifying, labeling, and completely processing the traumatic event can be targets for treatment through psychotherapy. The age of a person when they experience a traumatic event can also modulate the effects of the hippocampus. Particularly, the hippocampus is developing from birth to age 2 and is most vulnerable to the effects of stress during this time period. During adolescence the hippocampus is fully organized and less vulnerable to the effects of stress.
The hippocampus also has connections with the body's stress response system. The hippocampus is responsible for the negative feedback regulation of the Hypothalamic- pituitary-adrenal axis. Failure to regulate stress response through the HPA axis can have long-term health effects through the experience of chronic stress.
Interpersonal trauma
Interpersonal trauma is psychological trauma resulting from adverse interactions between people. Interpersonal trauma could include sexual violence, domestic violence, and abuse in childhood. People in these instances present with PTSD, often with more complex features. Interpersonal trauma continues to be a significant public health problem in the United States, contributing to significant psychological distress and functional impairment.
Sexual violence victims are predominantly women. When interviewing women who had been sexually abused in childhood, Williams found that 38% of women had no recollection of the abuse in later adulthood. While those who experienced a singular traumatic event (e.g., witnessing the death of a parent) were better able to remember the traumatic experience. These results indicate that repeated traumatic experiences are more likely to be repressed than those that occurred only once.
The World Health Organization has identified that one in three women are victims of intimate partner violence. Exposure to intimate partner violence results in many adverse psychological and neurological outcomes. Strangulation is common in interpersonal violence, causing cerebral dysfunction and leading to memory impairment. Initial consequences of strangulation could be loss of consciousness and mild brain injury, while long-term residual problems include neurological impairment. In a meta-analysis of primarily self-report responses from a female sample, women exposed to intimate partner violence are prone to experiencing loss of consciousness, mild brain injury, motor and speech disparities, memory loss, and lack of help-seeking behavior.
Treatment Individuals with a history of interpersonal trauma would benefit from psychoeducation concentrating on the manifestations of PTSD symptoms and trauma's consequences on memory may be beneficial. Some treatment approaches for survivors of interpersonal trauma also focus on memory restructuring. Trauma symptoms aid in preserving impaired memory; thus, restructuring memories through several possible treatment modalities can be advantageous in treating the trauma symptoms and patients' cognitions. These modalities include learning to address trauma memories by specifying triggers, re-conditioning flashbacks, and engaging in narrative restructuring. Additionally, some treatments aim to restructure memory through imagery and nightmare rescripting exercises. One consideration for therapists when suggesting memory restructuring to patients is the possible impact of prolonged exposure during treatment. Patients are required to describe trauma memories in great detail (e.g., imagery rescripting), which could lead to re-traumatization.
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. Missing memories, changes to memory, intensified memories – all are cases of manipulations of long-term memory. Within the construct of long-term memory, trauma has been shown to alter implicit and explicit memory. For example, sexual abuse victims with PTSD have been shown to present with explicit memory deficits. These alterations can even occur in individuals who did not develop PTSD from trauma exposure.
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. 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