Neural correlates of familiarity and conceptual fluency are dissociable at encoding

Familiarity and conceptual fluency belong to explicit and implicit memory respectively. Since familiarity and conceptual fluency co-occur at certain circumstances and share some similarities, it is difficult to distinguish them. By using ERPs, in present study, we sought to differentiate the Dm effects, the differential neural activities due to later memory performances, of familiarity and conceptual fluency at encoding. We used ancient pictographic characters as stimuli, which were categorized as high or low meaningfulness based on the subjective ratings. In Experiment 1, conceptual fluency was observed to be induced exclusively by the repetition of relative meaningful items. In Experiment 2, Dm effects of familiarity and conceptual fluency were observed, respectively. In addition, the distribution of conceptual fluency Dm effects was found to be more posterior than that of familiarity Dm effects. These findings provide the dissociation of familiarity and conceptual fluency at encoding and further support the distinction between explicit and implicit memory.