ERP recordings during a picture fragment completion task: effects of memory instructions

Sequential implicit (picture fragment completion) and explicit (free recall and recognition) memory tasks were performed by two groups of young adults. Subjects assigned to the intentional condition were asked to memorize the stimuli presented during the picture fragment completion task, whereas subjects assigned to the incidental condition were not so instructed. In the picture fragment completion task, all subjects showed savings (priming), i.e., their identification thresholds for previously seen fragments were lower than those for fragments not previously seen, and no between-group performance difference was found. Free recall performance was better for the intentional than the incidental group, but recognition performance did not differ between the groups. Despite similar between-group performance, event-related brain potentials (ERPs) recorded during the picture fragment completion and recognition tasks revealed between-group differences in information processing. The ERP data suggest that similar behavioral performance during memory tasks may have been associated with distinct neuronal mechanisms subserving priming and recollection.