The neurology of traumatic "dissociative" amnesia: Commentary and literature review

Background: The relationship between traumatic emotional stress, hippocampa l injury, memory loss, and traumatic ("dissociative") amnesia was examined. Method: A survey of the research on emotional trauma, learning, memory loss , glucocosteroid stress hormones, and the hippocampus was conducted, and an imal and human studies were reviewed. Results: it is well documented and has been experimentally demonstrated in animals and humans that prolonged and high levels of stress, fear, and arou sal commonly induce learning deficits and memory loss ranging from the mini mal to the profound. As stress and arousal levels dramatically increase,lea rning and memory deteriorate in accordance with the classic inverse U-shape d curve. These memory deficits are due to disturbances in hippocampal activ ation and arousal, and the corticosteroid secretion which can suppress neur al activity associated with learning and memory and induce hippocampal atro phy. Risk and predisposing factors include a history of previous emotional trauma or neurological injury involving the temporal lobe and hippocampus, the repetitive and prolonged nature of the trauma, and age and individual d ifferences in baseline arousal and level of cortisol. Conclusions: Although some victims may be unable to forget, amnesia or part ial memory loss is not uncommon following severe stress and emotional traum a. Even well publicized national traumas may induce significant forgetting. Memory loss is a consequence of glucocosteroids and stress-induced disturb ances involving the hippocampus, a structure which normally plays an import ant role in the storage of various events in long-term memory. (C) 1999 Els evier Science Ltd.