Does frequency matter? ERP and behavioral correlates of monitoring for rare and frequent prospective memory targets.

Behavioral and event-related potential (ERP) correlates of monitoring in an event-based prospective memory (PM) task were compared during blocks with rare versus frequent PM target presentations relative to an ongoing-task only condition. For both rare and frequent PM conditions, behavioral interference costs in terms of longer reaction times (RTs) were observed. Likewise, during both PM blocks a sustained ERP positivity with a frontal focus was identified on ongoing-task trials. While PM target identification and RT interference costs were larger during the PM-frequent relative to the PM-rare condition, the same sustained frontal positivity was observed during both PM blocks. These findings suggest that successful monitoring is associated with the adoption of a more general prospective retrieval mode, irrespective of target frequency. Moreover, preparatory attentional modulations directed at relevant target features played an important role for subsequent PM performance, as evident in larger P2 amplitudes during PM blocks.