Event-related potentials of verbal encoding into episodic memory: dissociation between the effects of subsequent memory performance and distinctiveness.

Episodic memory encoding and distinctiveness detection were examined using event-related potentials (ERP) in a single-trial word list learning paradigm with free recall following distraction. To manipulate distinctiveness, encoding of high- and very low-frequency words was contrasted. Amplitudes of the N400 and late positive component (LPC) were larger for low- than for high-frequency words, and ERPs were more positive for subsequently recalled than not recalled words. This subsequent memory effect was dissociated from the correlates of distinctiveness by polarity for the N400 and by time course for the LPC and dissociable into two effects. The data suggest that the first subsequent memory effect, which occurred for both word categories, is more directly related to episodic memory formation, whereas the second effect, which occurred for high-frequency words only, is related to processes influencing episodic encoding success indirectly.