Brain hearing activity. Coloured positron emission tomography (PET) scan data, showing brain activity (red) due to hearing an unknown language. The PET data has been laid over three-dimensional magnetic resonance imaging (MRI) scans of profiles of the left (left) and right (right) brain hemispheres, positioned with the front of the brain at far left and right. The red area is in the temporal lobe of the brain, responsible for hearing ability. The areas responsible for language comprehension have not been activated. For a PET image of the brain response to hearing a known language, see image P335/067.