Brain's taste centre. Coloured positron emission tomography (PET) scan of the brain during taste activity. The two hemispheres of the brain are at left and right, while the ventricles (cavities, black) are at lower centre. The PET scan has been superimposed onto a grey magnetic resonance imaging (MRI) scan. This is a coronal (vertical) section. The scan shows the level of brain activity associated with tasting, with the area of highest activity (white dot) in the sensory cortex. PET scans use radioactively-labelled substances introduced into the blood to view metabolic activity.