Electroencephalography: An Introduction
Electroencephalography (EEG) is a non-invasive method of measuring short-term brain activity. Electrodes placed on the scalp are used to record the electrical activity produced by neurons in the brain. When presented with a stimulus, the nervous system responds in a way that allows EEG measurement of brain wave activity. The recorded signal is called an evoked-response potential or event-related potential, depending on the nature of the task. Sensory evoked potentials (SEPs) can be distinguished according to the stimulus type (visual, somatosensory or auditory). Event-related potentials are thought to reflect cognitive processes like attention, memory, and language processing.
Research uses for EEG
EEG is frequently used in speech perception research. It provides a good measure of a person's ability to discriminate between sounds or groups of sounds, even passively. Use of EEG in speech production research is a little trickier, because the electrodes pick up electrical activity generated by the muscles of the face and mouth. By carefully taking out unwanted signals, it is possible to identify changes in perception during speech. There are also signals that occur before speaking that are associated with preparation for movement.