Brain activity reading braille. Coloured positron emission tomography (PET) scan of human brain areas active while reading braille writing. The left side of the brain is seen, with the front at left. Active parts of the folded cerebral hemis- phere are red/orange. Tactile areas (upper right) of the parietal cortex are activated as the blind person's fingers feel the braille dots. An area of cognition has also lit up at lower right. The scan involved injecting the radioactive isotope oxygen-15 into the bloodstream to allow areas of the brain with high metabolic activity to be seen.