Electroencephalography (EEG) By Michael C Levin, MD, College of Medicine, University of Saskatchewan Reviewed / Revised Jul 2021 | Modified Sep 2022 View Patient Education Twenty electrodes are distributed symmetrically over the scalp to detect electrical changes in the brain that are associated with Seizure disorders Sleep disorders Metabolic or structural encephalopathies The normal awake EEG shows 8 - to 12-Hz, 50 - mu V sinusoidal alpha waves that wax and wane over the occipital and parietal lobes and > 12-Hz, 10 - to 20-muV beta waves frontally, interspersed with 4 - to 7-Hz, 20 - to 100-muV theta waves.