





Cassinello's uncle picked him up from the accident scene and drove him to a hospital for a checkup. Apart from a few minor scratches, he was fine. But Cassinello says he has flashbacks to the disaster. "The images of shattered people in my cabin and outside are in my head," he says. Flashbacks are a normal part of the stress response. If Cassinello is lucky, the flashbacks will fade within weeks as he learns to suppress the bad memories cued up by triggers such as the sound of a train.

That process is called fear extinction. McIntyre and colleagues want to be able to influence it, so as to better help victims of post-traumatic stress disorder (PTSD). Scientists could activate a trauma victim’s vagus nerve, amplifying the memory-writing process while the patient practiced healthy responses to a fear-inducing stimulus. If the process works, it could speed up recovery. Other researchers are working on drug-enhanced fear extinction using chemicals such as zeta inhibitory peptide (ZIP) or D-cycloserine. Another approach, called fear reversal, aims to provoke fear-inducing memories into a malleable state, such as all memories enter when we access them, and then changing them with the help of a different drug, propranolol, which interferes with protein formation, or even with precisely timed talk therapy aimed at blocking the reconsolidation of bad memories.

One thing that is almost certain is that his memories of the event will change with time. Studies after the September 11, 2001, attacks on the World Trade Center found that New Yorkers' reports of their experience of the attack changed over the years.

For now, survivors of traumatic experiences such as Cassinello can lean on the trauma therapists who rushed to Santiago after the crash. Some 70 to 80 percent of car accident survivors get away without PTSD, McIntyre reckons. As Rodriguez points out, however, most of those therapists are volunteers in town for a few days. It may take a few weeks or even months of therapy for patients to get past the worst of their experiences.