The interpretation of surface recorded evoked potentials

Despite widespread application of surface-recorded evoked potential techniques, many neurophysiologists have been reluctant to use them for the study of brain function. Many serious problems attend the application of these techniques and their interpretation. First of all, surface potentials are very attenuated and are often difficult to distinguish from background noise. Second, the most commonly used approach to extract signal from noise is to average the raw data, a procedure which degrades the information content of the data. Third, the origins of surface potentials cannot be unambiguously reconstructed. Many signal processing strategies have been devised to overcome these limitations, with varying degrees of success. This article reviews some of these strategies and offers a guarded but optimistic view of the value of surface potential recording techniques.