Low frequency oscillations are responsible for changes in EEG complexity during wakefulness and sleep

Electroencephalography (EEG) is a technique for recording an electrogram of electrical activity on the scalp, which has been shown to represent the macroscopic activity of the brain's surface layer beneath. The electrodes are typically placed along the scalp, making it noninvasive. Electrocorticography, which uses invasive electrodes, is also known as "intracranial EEG.