An ERP Investigation Of Encoding And Retrieval In Directed Forgetting Effect

To forget irrelevant information effectively is as important as to remember useful information. To forget effectively may enhance the updating of memory and performances in memory process. Directed forgetting effect is the phenomenon that our memory has the ability of selectiveness, and we perform better for to be remembered items. There have been lots of surveys on directed forgetting, however, most of which are behavior experiments. Among the several surveys with event-related potential (ERP), few experiments involved both of encoding and retrieval, which may deepen the investigation of directed forgetting. The present survey tended to discuss the mechanism and psychological process of directed forgetting effect by investigating the relationship between item memory, source memory, Dm effect and directed forgetting effect.The present experiment collected data with ERP, and used the stimulus of two letters Chinese words in the item method directed forgetting paradigm. The experiment included three phases. Encoding phase: Subjects were instructed to remember or forget the word by the remember instructions appearing after each word. Item memory retrieval phase: Subjects were instructed to make old/new judgment. Source memory retrieval phase: Subjects were instructed to judge among the new words, the old red words and the old blue words. The order of the last two phases was balanced among subjects.The results indicated that, in encoding phase, there were directed forgetting effects found after the memory instructions appeared. To be remembered items were associated with a more positive ERP than to be forgotten items. Meanwhile, Dm effects in source memory were found in encoding phases after the instructions appeared. Moreover, the significant Dm effects were only the ones in recollection (Hit/Hit).The correctly judged old words were associated with more positive ERP than missed ones. And there was no significant difference between to be remembered items and to be forgotten items.In retrieval phase, there were directed forgetting effects both of the item memory and source memory, and the effects were bigger in source memory phases than that in item memory phases. The directed forgetting effects of source memory included the one based on recollection (Hit/Hit) and the one based on familiar (Hit/Miss) . The results revealed that, directed forgetting effects were more tightly related with the recollection retrieval.