The EEG or electroencephalogram is a test that allows the recording of brain activity. The EEG is absolutely painless. Electrodes are placed on the scalp and are connected to a monitor and a printer. Brain activity is transcribed as lines. These entries are evaluated by a neurologist who can determine whether they reveal a neurological abnormality. It may be performed during sleep or in the context of an activity, depending on the suspected abnormality. The EEG is mainly practiced for suspected epilepsy, sleep disorders, certain brain diseases. Two flat EEG's 4 hours apart is a sign of brain death.