MODEL RELEASED. Electroencephalography. Doctor monitoring a young boy's brain activity (brain waves) using an electroencephalography (EEG) machine. The boy is reading a book as the test is carried out. A number of small electrodes are taped to the boy's scalp. The electrodes detect the tiny electrical impulses produced by the activity of the brain. The brain waves are being displayed as graphs on the monitor. Characteristic brain wave patterns on the screen can be used to help diagnose medical conditions such as epilepsy, encephalitis, dementia, brain tumours and brain death.