An electroencephalogram (EEG) detects electrical activity in the brain. Electrodes are attached to the scalp and electrical activity shows up as wavy lines on the screen of an electroencephalogram monitor or printed out on paper from the monitor. A neurologist then interprets the reading to determine if it is normal or not. If not, the doctor may also be able to determine the type of abnormality and in which part of the brain the abnormality is occurring. The test is done under a number of conditions, such as when you are awake, when you are sleeping, during a seizure, when you are being stimulated with light, etc.