Accident gives clue to amnesia

It is the stuff of trashy Hollywood movies - a soldier suffers amnesia after a traumatic shock, attempts to help him fail and then, in the final reel, an accidental blow to the head preposterously restores the missing memories.

But this might not be so ludicrous after all. A team of doctors at the University of Malaga, Spain, have reported a bizarre case in the Journal of Neuropsychiatry and Clinical Neuroscience in which long-forgotten memories suddenly returned in the wake of a head injury.

The subject was a British soldier who fought in the Vietnam war. The man lost his Vietnamese wife and child when the refugee village they were staying in was attacked, while he was captured and tortured. Afterwards, as he recovered from the trauma, he could remember little of the horrors he had suffered. He later moved to Spain, remarried and led a happy life.

Several decades later, however, the veteran suffered a serious head injury in a car accident. After a fairly complete recovery from the wounds, he started to suffer vivid flashbacks about the attack on the village in Vietnam. During these episodes, he acted as though he were reliving the nightmare, complete with visual and auditory hallucinations. A brain scan revealed he had suffered a lesion to his right frontal lobe with a consequent reduction in blood flow.

The veteran's case is intriguing for several reasons, including the evidence it provides for the important role that repression plays in memory. Whether it is possible to repress traumatic events is the source of much dispute in cognitive science and is of particular legal importance in forensic psychology. The debate over false memory syndrome, for example, hinges on this issue.

Although it has recently been demonstrated under experimental conditions that repression can occur, the memories induced in subjects were, for obvious ethical reasons, non-traumatic.

The soldier's case suggests a positive role for repression in aiding recovery from trauma, as his successful reintegration into the community appeared linked to his previous inability to recall fully what had happened in Vietnam.

It also provides a clue as to where repression actually occurs - the right frontal area of the brain - and suggests that injury to this region can release previously "forgotten" memories.