Glossary
Event-related potential
What is an Event-Related Potential?
An event-related potential (ERP) is a measured brain response that is directly time-locked to a specific sensory, cognitive, or motor event. ERPs are extracted from EEG recordings by averaging brain activity across many trials to isolate the signal from background noise.
How it works
ERP components are voltage patterns defined by features such as timing, polarity, scalp distribution, and experimental sensitivity. They should not be treated as one-to-one readouts of particular mental processes. For example, the N400 is sensitive to the semantic context in which a word appears.
Other named components include P300, N170 and error-related negativity (ERN). They are studied in tasks involving attention, faces and performance monitoring, respectively, but none is a one-to-one label for a mental operation. What these signals mean depends on their timing and the experimental conditions.
Applied example
“I drink my coffee with cream and socks.” The last word does not fit. A sentence like this illustrates an N400 experiment: researchers compare responses to words that differ in how well they fit the preceding context. Unexpected words can produce a larger negative deflection around 400 milliseconds after they appear.
Why it matters
ERPs let researchers compare the timing of electrical responses on the scale of milliseconds. That makes them useful for studying what happens between an event and a response. Interpreting a peak still requires an experiment that distinguishes possible explanations.
Kutas and Hillyard’s N400 experiment (1984) linked the response to word expectancy and semantic association. The N400 is sensitive to context, not a unique detector of semantic mistakes.