MODEL RELEASED. EEG examination. 27-year-old woman undergoing an electroencephalograph (EEG) examination. Electrodes have been attached to her head. The EEG records the electrical activity from different parts of the brain, as it reacts to external visual or auditory stimuli (monitor, left). A computer maps an image of this activity, a process known as Brain Electrical Activity Mapping (BEAM, not shown). A comparison of the results is made with EEG data from a normal control subject and a colour map of statistical variance is produced, which can be used in the diagnosis of sensory defects.