Brain potentials reflecting spontaneous retrieval of emotional long-term memories

Recent ERP studies using immediate recognition suggest better recollection for emotional, relative to neutral, scenes when retrieved in tasks where memory is not explicitly probed. In the present study we examined ERPs associated with explicit and spontaneous retrieval using a long retention interval. In a between-group design, one week after incidental encoding of emotional and neutral scenes, participants performed either an explicit recognition task or a categorization task whilst viewing old and new pictures. Enhanced ERP old/new differences were found for emotional and neutral stimuli over frontal regions and selectively for emotional pictures over centro-parietal regions during explicit recognition, but not during categorization. During categorization, old/new differences were only present for emotional scenes over frontal regions. Taken together, spontaneous retrieval of emotional memories occurs even after long retention intervals and is probably based on familiarity.