Abstract
D.Litt. et Phil.
The evoked potential has proved to be one of the most important methods of studying brain function, specifically since it is a non-invasive or non-surgical method. The term evoked potential refers to a change in the pattern of the brain's electrical potential in response to an external stimulus. The external stimulus can be an auditory, visual or somatosensory stimulus. The evoked potential is measured by means of two electrodes connected to a recording apparatus such as the Nicolet Pathfinder. The difference in potential between the two active electrodes (bipolar recording) or the recording and reference electrodes (monopolar recording) is amplified and averaged over time by means of a computer to average transients. The development of the averaging computer was a major breakthrough in evoked potential research. The averaging technique assumes that the brain's sensory responses have an invariant time relationship to the evoking stimulus, whereas the ongoing background activity (EEG) does not. By averaging the electrical activity following the presentation of a stimulus, a small "signal" from the sensory pathway can be separated from the background "noise" of the EEG.
Over the past forty years, scalp recording of human sensory evoked responses has emerged as a useful technique for assessing sensory-pathway integrity, and it is now a standard tool in clinical neurology. Basic research on evoked responses has also addressed issues that may be more directly relevant to neuropsychology, such as identifying the evoked response measures corresponding to various stages of information-processing and cognitive functioning in both the intact and damaged brain...