Distinguishing strategic orienting toward memory age from retrieval difficulty: An ERP study

Abstract

ABSTRACTA well-established finding in episodic memory research is that the likelihood of successful retrieval is affected by the ‘age’ of the targeted memory (i.e. based on the duration of the encoding-retrieval interval). Although such findings are usually interpreted in terms of the memory trace changing in quality or accessibility over time, there is growing evidence that retrieval also depends on how well search attempts can be strategically oriented. Here, we investigated the strategic orienting of retrieval processing, as indexed by event-related brain potentials (ERPs), when retrieval was aimed toward candidate memories of different ages. As retrieving remote versus recent memories is associated with increased difficulty, the current study was designed to dissociate the difficulty and memory age effects. Subjects encoded two lists of pictures separated by one week, with the items in each list presented once or four times. A series of memory tests targeting pictures from only one week-by-repetition condition at a time were then completed, while new pictures and those from the other conditions were rejected. Consistent with previous results, new-item ERPs were more positive over posterior scalp when recent compared to remote lists were targeted. Importantly, this difference remained when difficulty was matched, and the ERP correlates of difficulty were distinct in both timing and polarity from those of orienting. Together, these findings provide further support for the idea that the age of a targeted memory alone can lead to the adoption of retrieval orienting strategies.