MEMORY LOSS SECONDARY TO PTSD

~Mehrun Nisa~ 

PTSD occurs in individuals exposed to exceptionally severe trauma. According to the fourth edition of the Diagnostic and Statistical Manual (DSM-IV; American Psychiatric Association [APA], 1994), PTSD is characterized by three symptom clusters: (1) re-experiencing the trauma (e.g., flashbacks, nightmares), (2) avoidance behaviors (e.g., avoiding reminders of the trauma, social withdrawal), and (3) increased physiological arousal (e.g., hypervigilance, exaggerated startle response). The APA first recognized PTSD as a distinct diagnosis in 1980 with its inclusion in the third edition of the DSM. 

This paper aims to review the literature on non-trauma-related episodic memory functioning in individuals with PTSD and to evaluate the evidence that the disorder is associated with a particular pattern of memory dysfunction. While PTSD is often related to trauma-related memory dysfunction, an alternative hypothesis suggests that the memory deficits in PTSD may stem from underlying attention and concentration deficits rather than trauma itself. (Stein, Hanna, Koverola, Torchia, & McClarty, 1997). 

People with PTSD often report difficulties remembering day-to-day information unrelated to their traumatic episode. Structural and functional imaging techniques have identified abnormalities in brain regions critical for memory functioning, which may further explain these deficits. Nevertheless, studies investigating cognitive functioning in people with PTSD have produced inconsistent results. This review aims to investigate studies reporting performance on tests of episodic memory. Specifically, papers were examined concerning the hypothesized memory functions of the frontal lobes, the hippocampus, and the amygdala. It is concluded that while there is reasonable evidence of frontal lobe involvement, memory deficits linked to hippocampal dysfunction have been harder to identify. Although no published studies directly examine the involvement of the amygdala, preliminary evidence suggests that dysfunction in this region may contribute to memory deficits in PTSD. Reasons for the inconclusiveness of the results are discussed. 

Disturbances in aspects of memory described in current learning and cognitive theories are much more strongly associated with the presence of psychiatric disorders than with mere exposure to traumatic events. In posttraumatic stress disorder (PTSD), numerous associated changes involve memory capacity, the content of trauma memories, and a variety of memory processes. Whereas some changes appear to reflect the effects of the disorder, other evidence supports a predictive or causal role for memory disturbance. The following aspects of memory are likely to play a causal role in the development or maintenance of PTSD: verbal memory deficits, negative conceptual knowledge concerning the self, over-general memory, avoidance or suppression of memories, and negative interpretation of memory symptoms. Other aspects of memory likely to play a causal role that is in addition specific to PTSD are the integration of the trauma with identity, impairment in the retrieval of voluntary trauma memories, and increased incidence of sensation-based memories or flashbacks. 

Evidence on intrusive memories and deficits in declarative memory function in individuals with PTSD is reviewed about three brain areas that are involved in memory functioning and the stress response: the hippocampus, amygdala, and prefrontal cortex. Neurobiological studies have shown that the noradrenergic stress system is involved in enhanced encoding

of emotional memories, sensitization, and fear conditioning, through its effects on the amygdala. Chronic stress also affects the hippocampus, a brain area involved in declarative memories, suggesting that hippocampal dysfunction may partly account for the deficits in declarative memory in individuals with PTSD. Deficits in the medial prefrontal cortex, a structure that normally inhibits the amygdala, may further enhance the effects of the amygdala, thereby increasing the frequency and intensity of the traumatic memories. Thus, by its influence on these brain structures, exposure to severe stress may simultaneously result in strong emotional reactions and difficulties recalling the emotional event. 

REFERENCES 

Brewin, C. R. (2011). The nature and significance of memory disturbance in posttraumatic stress disorder. Annual Review of Clinical Psychology, 7(1), 203-227. 

Isaac, C. L., Cushway, D., & Jones, G. V. (2006). Is posttraumatic stress disorder associated with specific deficits in episodic memory? Clinical Psychology Review, 26(8), 939–955. 

Elzinga, B. M., & Bremner, J. D. (2002). Are the neural substrates of memory the final common pathway in posttraumatic stress disorder (PTSD)? Journal of Affective Disorders, 70(1), 1–17.