On the in Dependence of the Cnv a N D the P300 Components of the H U M a N Averaged Evoked Potential 1 Emanuel Donchin, Patricia Tueting, Walter Ritter, Marta Kutas and Earle Heffley

The form of the average cortical potential is determined both by the physical characteristics of the eliciting stimulus and by the nature of the information processing activities invoked by that stimulus. In particular, much evidence has shown that P300, a component with a positive polarity, and a modal latency of about 300 msec, is considerably enhanced in the average evoked potential (ALP) when the eliciting stimulus invokes information processing activities (Donchin and Cohen 1967; Donchin et al. 1973). The evidence is strong that P300 represents endogenous cortical processes (Sutton et al. 1967; Klinke et al. 1968; Weinberg et al. 1970). It has been suggested by several investigators (Karlin 1970; N/i~it~inen 1970) that the amplitude of P300 is determined by generalized preparatory activity preceding the eliciting stimulus rather than by processes invoked by the stimulus. Such accounts for P300 stress that in most experimental circumstances in which P300 is enhanced by the eliciting stimulus it is preceded by a contingent negative variation (CNV). This event-related potential (ERP) has been shown to precede forewarned events requiring a response by the subject (Walter et al. 1964). It has been proposed therefore that P300 is essentially a reflection of the CNV preceding the eliciting stimulus. This argument has taken several different forms,