ANATOMICAL and physiological studies have shown that there is an area specialized for the processing of colour (area V4) in the prestriate cortex of macaque monkey brain1. Earlier this century, suggestive clinical evidence for a colour centre in the brain of man2,3 was dismissed4-8 because of the association of other visual defects with the defects in colour vision4,5,7. However, since the demonstration of functional specialization in the macaque cortex9, the question of a colour centre in man has been reinvestigated,based on patients with similar lesions in the visual cortex10-12. In order to study the colour centre in normal human subjects, we used the technique of positron emission tomography (PET), which measures increases in blood flow resulting from increased activity in the cerebral cortex. A comparison of the results of PET scans of subjects viewing multi-coloured and black-and-white displays has identified a region of normal human cerebral cortex specialized for colour vision.
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