Expectations modulate early but not late event-related potential correlates of successful recognition memory
Recognizing that an item has been previously encountered may not only depend on the strength of memory for that item, but also the expectation that the item will be remembered. Recent studies by O’Connor, et al (2010) and Jaeger et al (2013) revealed that a significant portion of the functional magnetic resonance imaging (fMRI) “retrieval success” effect (BOLD signal for correctly identified old items > new items) depends upon whether participants expect novel or familiar stimuli. The current study examined how expectancy modulates the event-related potential (ERP) retrieval success effect. We employed a typical recognition memory task with the addition of explicit cues indicating if upcoming memory probes were “likely old”, “likely new” (with 75% validity), or “unknown”. An electrophysiological response to the cue, primarily across frontal electrodes from 700-850ms after cue onset, predicted individual differences in cue- induced bias in memory judgments. Responses to memory probes were examined 300- 400ms and 500-700ms after probe onset, corresponding to time windows previously associated with ERP correlates of memory processing. Differences between old and new items were greatest from 300-400ms when preceded by “likely old” cues, overlapping with a component previously identified as tracking familiarity-based processing. In contrast, the 500-700ms time window, previously associated with recollection, revealed significant differences between old and new items that were not modulated by cue type. Overall this pattern of results shows that cue induced biases influence earlier (300-400ms after onset of a memory probe) but not later retrieval processing (500-700ms).