Thursday, May 13, 2010
EEG (electroencephalography) uses scalp electrodes to measure electrical field potentials that result from brain activity. Many EEG studies focus on event related potentials (ERP), patterns of activity that occur in response to a stimulus or cognitive event (Hence, they’re “event related.”).
Usually, an experimenter averages the brain response over many trials to achieve adequate signal to noise ratio. The end result is a waveform representing the average pattern over trials of a certain type. Peaks and troughs in waveform are known as components. While the naming of components isn’t systematic, they are often named with a letter (P if it’s a peak in the positive direction and N if it’s in the negative direction), and a number that either corresponds to the approximate time of the peak or its order of appearance. Commonly studied components include the N400 and P300. To learn more about how ERPs are used in research, take a look at entries with the EEG label.