The Endogenous Components of the Event-Related Potential -- A Diagnostic Tool?

This chapter introduces the conceptual foundations of a theory-based approach to the use of event-related brain potential (ERPs), in contrast to a nosological approach. The chapter provides description of a series of the studies of P300 in aged subjects conducted in laboratory that serves to illustrate an approach to the use of ERPs in cognitive psychophysiology. The degree to which the increase in P300 latency is indeed a specific indicator of senile dementia has proven somewhat controversial. Increases in P300 latency do tend to occur in association with other pathologies. The starting point for a nosological study is the availability of groups of clinically diagnosed patients, as well as an adequate control group of non-patients. The strategy is empirical. Given that the studied groups are known to be proper representatives of the diagnostic classes of interest, then any measure that discriminates among the groups is potentially useful. This approach has, for example, been of great benefit in developing a diagnostic measure for multiple sclerosis based on the latency of brain responses elicited by moving checkerboards. However, the success of the nosological approach is contingent on the specificity of the deficit and the certainty with which patients can be diagnosed clinically