An event-related potential (ERP) is any stereotyped electrophysiologicalresponse to an internal or external stimulus. More simply, it is any measured brainresponse that is directly the result of a thoughtor perception.
- 1 Measurement
- 2 Clinical ERP
- 3 Research ERP
- 4 See also
ERPs can be reliably measured using an electroencephalography(EEG), a device that measures electricalactivity of the brain through the skulland scalp. As the EEG reflects thousands of simultaneously ongoing brain processes, the brain response to a certain stimulus or event of interest is usually not visible in the EEG. One of the most robust features of the ERP response is a response to unpredictable stimuli. This response-known as the P300(or simply "P3")-manifests as a positive deflection in voltageapproximately 300 millisecondsafter the stimulus is presented.
In actual recording situations, it is difficult to see an ERP after the presentation of a single stimulus. Rather the most robust ERPs are seen after many dozens or hundreds of individual presentations are averagedtogether. This technique cancels out noisein the data allowing only the voltage response to the stimulus to stand out clearly.
While evoked potentialsreflect the processing of the physical stimulus, event-related potentials are caused by the "higher" processes, that might involve memory, expectation, attention, changes in the mental state etc.
Physiciansand neurologistswill sometimes use a flashing visualcheckerboard stimulus to test for any damage or trauma in the visual system. In a healthy person, this stimulus will elicit a strong response over the primary visual cortexlocated in the occipital lobein the back of the brain.
Experimental psychologistsand neuroscientistshave discovered may different stimuli to elicit reliable EEG ERPs from participants. The timing of these responses is thought to provide a measure of the timing of the brain's communication or time of information processing. For example, in the checkerboard paradigm described above, in healthy participants the response of the visual cortex is around 150-200ms. This would seem to indicate that this is the amount of time it takes for the transduced visual stimulus to reach the cortexafter lightfirst enters the eye. Alternatively, the P300 response occurs at around 300ms regardless of the stimulus presented: visual, tactile, auditory, etc. Because of this general invariance in regard to stimulus type, this ERP likely reflects a higher cognitive response to new stimuli.
- Evoked potential
- Induced activity
- N400de:Ereigniskorrelierte Potenziale
This article is licensed under the GNU Free Documentation License.
It uses material from the http://en.wikipedia.org/wiki/Event-related+potential Wikipedia article Event-related potential.