Trauma and Flashing Lights
Psychologists say they might be able to prevent or treat post-traumatic stress disorder using glasses with a pair of flashing lights.
Dr Peter Naish of the Open University said that sufferers process the lights in their brains in the same way as people in a hypnotic state.
Sometimes they can believe that their flashbacks are real, and that real life is just a dream. And this is echoed in how they use their brains to see the lights.
Dr Naish said that some trauma survivors seem to be in a hypnotic state most of the time, and can suffer from extreme hallucinations.
In the case of one of the survivors of the London tube bombings of 2005, he said: "In her flashbacks, she thought she was in one of the trains still and was going to die, and in the much longer moments of lucidity, she thought she was lapsing into unconsciousness and her brain was playing tricks." For this woman, this state of confusion went on for a few days, and for at least a year clear flashbacks of the trauma continued.
Dr Naish and his colleague Dr Ksenja da Silva have developed a piece of equipment that may be able to work out who is at risk of the disorder. They use an ordinary pair of sunglasses, with a light at each side, on the outside corner of the lens.
People put on the glasses and the lights are flashed one after another. The subject is then asked to tell the person running the experiment which light came on first.