Phonological/semantic word recognition. Coloured Positron Emission Tomography (PET) scan of areas of the brain involved in processing words. Active areas on the left-side of the brain are in red and yellow. In a phonological task (at top), meaning- less sounds are listened to for word recognition. The superior temporal and inferior frontal areas are active, particularly the hearing" region of the brain. In a semantic task (at bottom), heard words are listened to for their meaning. Superior frontal, parietal and temporal areas are active, in the intellectual processing of words. Active areas show cerebral blood flow detected by PET."