Scientists believe they have found a way to probe the mysterious phenomenon of feeling you have witnessed something before - deja vu. Leeds Memory Group researchers say they have gone some way to recreating the sensation in the lab using hypnosis. New Scientist magazine reports the researchers hope their work will shed light on the fundamental workings of the human memory. It is estimated that as many as 97% of people have experienced deja vu. In some severe cases it can be distressing to the point of causing depression and some sufferers have been prescribed anti-psychotic medication. However, experts suspect that many people who experience the sensation are unwilling to discuss it with their doctor. Two key processes are thought to occur when someone recognises a familiar object or scene. First, the brain searches through memory traces to see if the contents of that scene have been observed before. If they have, a separate part of the brain then identifies the scene or object as being familiar. In deja vu, this second process may occur by mistake, so that a feeling of familiarity is triggered by a novel object or scene. The Leeds team set out to create a sense of deja vu among volunteers in a lab. They used hypnosis to trigger only the second part of the recognition process - hoping to create a sense of familiarity about something a person had not seen before. The researchers showed volunteers 24 common words, then hypnotised them and told them that when they were next presented with a word in a red frame, they would feel that the word was familiar, although they would not know when they last saw it. Green frames would make them think that the word belonged to the original list of 24.
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