How Memory Task And Word Frequency Influence Directed Forgetting:An ERP Study

Directed forgetting(DF)is commonly adopted to investigate memory control,or intentional remembering and forgetting.Studies using the item method of DF have consistently observed that "to-be-remembered"(TBR)items,following"Remember"(R)cues,have better performance than "to-be-forgotten"(TBR)items,following "Forget"(F)cues,defined as the DF effect.The mechanisms underlying the DF effect may include selective rehearsal for TBR items and active inhibition for TBF items.According to dual-process models,recognition reflects two distinctive memory processes,familiarity and recollection.Previous research has concluded that the retrieval of TBF items mainly relies on familiarity,and the retrieval of TBR items is based on both familiarity and recollection.To further explore DF and related neural mechanisms,the current study would like to introduce into DF two factors,memory task and word frequency.First,by adding source memory task,versus item recognition,relevant conclusions would be more compelling;second,high and low frequency words associate with different encoding and retrieval characteristics,which would be helpful to detect both encoding and retrieval within DF.We carried out two ERP(event-related-potential)experiments,corresponding to item recognition and source memory task separately.We used two-character Chinese words of high and low frequency as stimuli.The two experiments were almost identical except that Experiment 1 asked for old/new judgments,while Experiment 2 required TBF/TBR/new judgments.Our results showed that,first,during source memory task,low-frequency TBF and TBR items evoked comparable LPC,indicating recollection of similar level.Second,under low frequency condition,retrieval of TBF items elicited significant FN400 and LPC,indexing familiarity and recollection for processing TBF items.Third,to suppress high-frequency TBF items in item recognition task,and low-frequency TBF items in source memory task,could elicit significant increased frontal positivity for F cues versus R cues,reflecting the role of active inhibition.The current study confirmed that within the recollection-based source memory task,retrieving TBF items also evokes reliable recollection;under low frequency condition,retrieving TBF items elicits both familiarity and recollection;memory task and word frequency have an interactive influence on active inhibition.