Electroencephalography

Electroencephalography (EEG) records voltage differences produced by brain activity using electrodes on the scalp or, in specialized procedures, within the brain. Its high time resolution makes it useful for tracking rapid changes in neural activity.

Electroencephalogram: A time-varying record of voltage differences measured by electroencephalography. The recorded waveform is the direct output of an EEG examination.
Electroencephalography in epilepsy: The use of EEG to detect and characterize abnormal electrical activity associated with epilepsy. Interictal spikes and recorded seizures can help classify seizure disorders and guide care.
Magnetoencephalography: A method that measures magnetic fields produced by electrical activity in the brain. MEG detects related neural activity without scalp voltage measurements, but requires specialized sensors.
Richard Caton: A British physician who recorded electrical activity from exposed animal brains in the nineteenth century. Caton's experiments supplied early evidence that brain tissue generates measurable electrical signals.
EEG source localization: Methods for estimating the brain sources that produced measured scalp EEG signals. Inferring precise sources from scalp voltages is difficult because many source patterns can fit the same measurements.
Action potential: A rapid electrical impulse that travels along the membrane of an excitable cell. Neural action potentials contribute to brain activity, though scalp EEG mainly reflects synchronized postsynaptic currents.
Sleep electroencephalography: The use of EEG patterns to identify sleep stages and characterize sleep-related events. Changes in EEG rhythms help distinguish wakefulness, sleep stages, and abnormal events during sleep.
Functional magnetic resonance imaging: An imaging method that estimates brain activity from changes in blood oxygenation. fMRI localizes activity more precisely in space, while EEG tracks changes more quickly in time.
Hans Berger: A German psychiatrist who published the first human EEG recordings in 1929. Berger established scalp recording as a method for studying electrical activity in the human brain.
EEG inverse problem: The underdetermined problem of inferring neural sources from measured electrical potentials. The inverse problem limits how confidently EEG can identify the location and extent of active brain regions.

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