An Analysis of Preparation and Response Activity in P300 Experiments in Humans

Abstract

The limitations of the averaging technique in studies of sensory evoked potentials (EPs) and “endogenous” event-related potentials (ERPs) have been discussed by various authors (Sayers 1974; Basar et al. 1975, 1976a, b; Squires and Donchin 1976; Van der Tweel et al. 1980). These authors have questioned the assumptions underlying the averaging technique (identical stimuli, identical responses, and random stationary background EEG activity that is not correlated with the EP and ERP response) and have suggested that EP and ERP slow potentials may be manifestations of stimulus-evoked and response-evoked synchronization, frequency stabilization, frequency selective enhancement and damping, and phase reordering of spectral components of the spontaneous EEG activity already present. That is to say, these slow potentials signify a dynamic change in the spontaneous EEG activity associated with an “event” of signal or information processing in the brain. From this perspective, the “background” EEG activity should not be considered as “noise” that has to be averaged out, nor should the EP and ERP signal be interpreted in terms of some “additive component” to the spontaneous EEG activity.