Event-related brain potential examination of implicit memory processes: masked and unmasked repetition priming.

The proposition that cortically based perceptual representation systems (PRSs) are responsible for some implicit priming phenomena was examined by using event-related potentials (ERPs) in repetition and masked word priming. Experiment 1 used an explicit recognition task, in which repeated words replicated previous ERP repetition priming effects, whereas masked repetition priming revealed a new ERP effect with a posterior topography. Experiment 2 demonstrated ERP and behavioral priming in a lexical decision task for repetition and masked repetition priming. Topographical mapping of ERP repetition priming effects involved both early and late effects over the right and left anterior regions, whereas masked priming produced only an early ERP effect posteriorly. These results suggest differences between early and late ERP priming effects in terms of explicit recollection. Moreover, a posterior PRS may not be involved in some longer term implicit repetition priming effects.