Brain activity reading braille. Coloured positron emission tomography (PET) scans of human brain areas active while reading braille writing. The left sides of the brains are seen, with their fronts at left. Active parts of the folded cerebral hemisphere are red/orange. Tactile areas (upper centre on both scans) of the parietal cortex are activated as the blind person's fingers feel the braille dots. Areas of cognition have also lit up at lower right on both scans. 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.