Geoff Watts meets researchers attempting to unlock the mysteries of hallucination as well as some of those who experience the phenomenon. Hallucinations aren't what they used to be. Time was when reporting a divine vision would bring fame or fortune. The Enlightenment changed all that and nowadays you'd be more at risk of being handed a prescription for a major tranquilliser for reporting what you saw or heard.

Hallucinating, in essence, the experience of seeing or hearing (and sometimes smelling or touching) something that by any objective measure, isn't there, has been linked to a wide variety of causes. But there are also examples of otherwise 'healthy' individuals who have experienced vivid and sometimes distressing hallucinations. With the advent of fMRI scanning, researchers can observe the hallucinating brain in action, it is these 'healthy' individuals who are beginning to open the doors of perception and which may provide new insights and treatments for psychosis and schizophrenia.

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