Memory for perceived and imagined pictures: An event-related potential study

Event-related potentials (ERPs) and behavioral measures were used to investigate recognition memory and source-monitoring judgements about previously perceived and imagined pictures. At study, word labels of common objects were presented. Half of these were followed by a corresponding picture and the other half by an empty frame, signalling to the Ss (aged 20-35 yrs) to mentally visualize an image. At test, Ss in a source-monitoring task made a 3-way discrimination between new words and words corresponding to previously perceived and imagined pictures. Ss in an old/new-recognition task indicated whether test words were previously presented or not. In both tasks, correctly identified old items elicited more positive-going ERPs than correctly judged new items. This widely distributed old/new effect was found to have an earlier onset and to be of a greater magnitude for imagined than for perceived items. Task affected the old/new effects over prefrontal areas and the reaction times to remembered old items. Findings are consistent with the view that a greater amount, or a different type, of information is necessary for accurate source-memory judgements than for correct recognition, and moreover, that different types of source-specifying information revive at different rates.