Selective Forgetting & Traumatic Coping
As noted earlier thought suppression paradigms illustrate that thought inhibition can induce impairments in the ability for retrieving properly sequenced film narrative memory, reduce coherency, produce “snapshots” of events, and increase thought preoccupation in healthy subjects (Harvey & Bryant, 1998a). Interestingly, these behaviors also characterize PTSD’s symptoms of avoidance and hotspot perceptual memories (Ehlers, Hackmann, & Michael, 2004; Berntsen & Rubin, 2006) as well as PTSD trauma narratives, which lack coherency and temporal sequencing (Foa, Molnar & Cashman, 1995; Hembree & Foa, 2000;). Patients with either acute stress disorder (ASD), a disorder characterized by early reactive symptoms of avoidance, intrusion, numbing, and anxiety to a recently experienced trauma (APA, 1994), or those with chronic PTSD (3-192 months post trauma) tend to experience a rebound effect and increased traumatic thoughts after being required to suppress traumatic thoughts earlier (Harvey & Bryant, 1998b). This effect has also been accompanied by intact thought suppression abilities and greater perceived difficulty in the trauma survivor’s ability for being able to control trauma-related thoughts (Shipherd & Beck, 1999). In a directed forgetting paradigm newly exposed trauma survivors with ASD have demonstrated learning impairments despite opportunities for post-learning retrieval. They also present enhanced suppression abilities needed for the directed forgetting task and superior abilities at forgetting (Moulds & Bryant, 2002).
Also noted earlier inhibitory mechanisms deactivating the retrieval of declarative mental representations center in the dorsal and ventrolateral PFC in concert with the dorsal pACC. This region’s interactions with the stress-related amygdala may allow expression of the sustained conditioning state while impairing hippocampal declarative processing. This supports Anderson’s conclusion, which is based on Bechara and colleagues’ (1995) research findings noted earlier (Bechara, Tranel, Damasio, Adolphs, Rockland, & Damasio, 1995), that “it may be possible to suppress (through self-thought suppressive processes) the declarative representation of trauma without altering a person’s conditioned emotional responses to trauma-related stimuli” (Anderson, 2001, p. 200).
References
American Psychiatric Association (APA) (1994). Diagnosis and Statistical Manual of Mental Disorders of Mood Disorders, 4th Ed. Washington, D.C.: American Psychiatric Association.
Anderson, M.C. (2001). Active forgetting: Evidence for functional inhibition as a source of memory failure. Journal of Aggression, Maltreatment, & Trauma, 4, 185-210.
Bechara, A., Tranel, D., Damasio, H., Adolphs, R., Rockland, C., & Damasio, A.R. (1995). Double dissociation of conditioning and declarative knowledge relative to the amygdala and hippocampus in humans. Science, 269(5227), 1115-8.
Berntsen, D. & Rubin, D.C. (2006). Flashbulb memories and posttraumatic stress reactions across the life span: age-related effects of the German occupation of Denmark during World War II. Psychology and Aging, 21(1), 127-139.
Ehlers, A., Hackmann, A., & Michael, T. (2004). Intrusive re-experiencing in post-traumatic stress disorder: phenomenology, theory, and therapy. Memory, 12(4), 403-415.
Foa, E.B., Molnar, C., & Cashman, L. (1995). Change in rape narratives during exposure therapy for posttraumatic stress disorder. Journal of Traumatic Stress, 8(4), 675-690.
Harvey, A.G., & Bryant, R.A. (1998a). The role of valence in attempted thought suppression. Behaviour Research and Therapy, 36(7-8), 757-763.
Harvey, A.G., & Bryant, R.A. (1998b). The effect of attempted thought suppression in acute stress disorder. Behaviour Research and Therapy, 36(6), 583-590.
Hembree, E.A., & Foa, E.B. (2000). Posttraumatic stress disorder: Psychological factors and psychosocial interventions. Journal of Clinical Psychiatry, 61 Supplement 7, 33-39.
Moulds, M.L., & Bryant, R.A. (2002). Directed forgetting in acute stress disorder. Journal of Abnormal Psychology, 175-179.
Shipherd, J.C., & Beck, J.G. (1999). The effects of suppressing trauma-related thoughts on women with rape-related posttraumatic stress disorder. Behaviour Research and Therapy, 37(2), 99-112.