Event-related potential (ERP) evidence for source-monitoring based on the absence of information

Event-related potentials (ERPs) were recorded during a reality monitoring (RM) task (i.e., discriminating between seen and imagined words) and during an internal source monitoring (ISM) task (i.e., discriminating between self-generated and imagined words). Behavioral measures indicated robust recollection during both tests with greater recollection during ISM. The ERP correlate of recollection, the parietal old/new effect, was observed for both seen and imagined words during RM but only for self-generated words during ISM. This evidence indicates that self-generated information was diagnostic of source and that recollection of imagined words was based on the absence of self-generated information during ISM. The late posterior negativity (LPN) ERP old/new effects were observed for all conditions; however, the generated word LPN was attenuated during ISM. This pattern is consistent with the hypothesis that it reflects continued evaluation of trace information and suggests that recovery of self-generated information does not initiate an extensive evaluation of memory characteristics.