At the midpoint of the 1990s, the much-hyped Decade of the Brain, Peter Brook directed a stage version of Oliver Sacks’s book The Man Who Mistook His Wife for a Hat at the Cottesloe in London. At one point a patient was presented to a neurologist with a condition known as visual agnosia. The patient watched a screen on which a video of a seashore was depicted. He could describe moving white and blue lines and a strip of yellow: but he could not put it together to say what it was. At the end of the play, all the cast of patients and neurologists came on stage to watch another video: it depicted a PET scan showing the map of a brain gently pulsing in vivid colours. Brook meant his audience to grasp that brain imaging, as a way of understanding the mind, is as empty of meaning as impressions on a patient with visual agnosia.