Effects of Age on Prestimulus Neural Activity Predictive of Successful Memory Encoding: An fMRI Study

Abstract

Prestimulus subsequent memory effects (SMEs)-differences in neural activity preceding the onset of study items that are predictive of later memory performance-have consistently been reported in young adults. The present functional magnetic resonance imaging experiment investigated potential age-related differences in prestimulus SMEs. During study, healthy young and older participants made one of two semantic judgments on images, with the judgment signaled by a preceding cue. In test phase, participants first made an item recognition judgment and, for each item judged old, a source memory judgment. Age-invariant prestimulus SMEs were observed in left dorsomedial prefrontal cortex, left hippocampus, and right subgenual cortex. In each case, the effects reflected lower blood oxygen level dependent signal for later recognized items, regardless of source accuracy, than for unrecognized items. A similar age-invariant pattern was observed in left orbitofrontal cortex, but this effect was specific to items attracting a correct source response compared to unrecognized items. In contrast, the left angular gyrus and fusiform cortex demonstrated negative prestimulus SMEs that were exclusive to young participants. The findings indicate that age differences in prestimulus SMEs are regionally specific and suggest that prestimulus SMEs reflect multiple cognitive processes, only some of which are vulnerable to advancing age.

Keywords: aging; episodic memory; preparation; prestimulus; proactive control; subsequent memory effect.