What is Electroencephalography?
Electroencephalography (EEG) is a neuroimaging technique that records electrical activity from the scalp, providing millisecond-level temporal resolution of brain activity. It measures the synchronized electrical potentials generated by large populations of neurons.
How it works
EEG records voltage fluctuations using electrodes placed on the scalp. Its main advantage is temporal resolution (detecting changes within milliseconds), making it ideal for studying the timing of cognitive processes. Its main limitation is spatial resolution (it cannot precisely localize where in the brain activity originates). EEG is widely used to study event-related potentials (brain responses to specific stimuli), oscillatory activity (rhythmic patterns linked to cognitive states), and clinical conditions (epilepsy, sleep disorders).
Applied example
A researcher studying decision-making places an EEG cap on a participant and measures the error-related negativity (ERN) signal that appears within 80 milliseconds of making an error, long before the person is consciously aware of the mistake. This reveals that the brain detects errors before conscious awareness.
Why it matters
EEG provides a window into the brain’s real-time information processing, capturing cognitive events that occur too quickly for behavioral observation.
