Image of the brain of a dyslexic boy produced by brain electrical activity mapping (BEAM). The process maps the degree of difference between each spot on a normal brain and a corresponding spot on an abnormal brain. The colour-coded computerised picture is collated from EEG data recorded in response to various applied stimuli (so-called evoked potential measurement).The brightest areas on the map are where these measured differences are greatest, in this case showing an abnormal theta pattern over the left frontal lobe of the brain.