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Despite limited spatial resolution, EEG continues to be a valuable tool for research and diagnosis. EEG used to be a first-line method of diagnosis for tumors, stroke and other focal brain disorders, but this use has decreased with the advent of high-resolution anatomical imaging techniques such as magnetic resonance imaging (MRI) and computed tomography (CT). It is also used to diagnose sleep disorders, depth of anesthesia, coma, encephalopathies, and brain death. The latter analyses the type of neural oscillations (popularly called "brain waves") that can be observed in EEG signals in the frequency domain.ĮEG is most often used to diagnose epilepsy, which causes abnormalities in EEG readings. The former investigates potential fluctuations time locked to an event, such as 'stimulus onset' or 'button press'. Diagnostic applications generally focus either on event-related potentials or on the spectral content of EEG. Clinically, EEG refers to the recording of the brain's spontaneous electrical activity over a period of time, as recorded from multiple electrodes placed on the scalp.

Electrocorticography, involving invasive electrodes, is sometimes called intracranial EEG.ĮEG measures voltage fluctuations resulting from ionic current within the neurons of the brain. It is typically non-invasive, with the electrodes placed along the scalp. Electroencephalography ( EEG) is a method to record an electrogram of the electrical activity on the scalp that has been shown to represent the macroscopic activity of the surface layer of the brain underneath.