Effects of age on pre-stimulus neural activity predictive of successful memory encoding: an fMRI study

Pre-stimulus 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 fMRI experiment investigated potential age-related differences in pre-stimulus 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 the test phase, participants first made an item recognition judgment and, for each item judged old, a source memory judgment. Age-invariant pre-stimulus SMEs were observed in left dorsomedial prefrontal cortex, left hippocampus, and right subgenual cortex. In each case, the effects reflected lower BOLD signal for later recognized items, regardless of source accuracy, than unrecognized items. A similar age-invariant pattern was observed in left orbitofrontal cortex, but the effect in this region was specific to items attracting a correct source response compared to unrecognized items. In contrast, the left angular gyrus and fusiform cortex demonstrated negative pre-stimulus SMEs that were exclusive to young participants. The findings indicate that age differences in pre-stimulus SMEs are regionally specific and suggest that pre-stimulus SMEs reflect multiple cognitive processes, only some of which are vulnerable to advancing age.