Age differences in neural distinctiveness during memory retrieval versus reinstatement

Robust evidence points to mnemonic deficits in older adults related to dedifferentiated, i.e., less distinct, neural responses during memory encoding. However, less is known about retrieval-related dedifferentiation and its role in age-related memory decline. In this study, younger and older adults were scanned both while incidentally learning face and house stimuli and while completing a surprise recognition memory test. Using pattern similarity searchlight analyses, we looked for indicators of neural dedifferentiation during retrieval and asked whether this might explain interindividual differences in memory performance. Our findings revealed age-related reductions in neural distinctiveness during memory retrieval as well as in encoding-retrieval reinstatement in visual processing regions. We further demonstrated that the degree to which patterns elicited during encoding were reinstated during retrieval tracked variability in memory performance better than retrieval-related distinctiveness only. All in all, we contribute to meager existing evidence for age-related neural dedifferentiation during memory retrieval. We propose that the recognition task (as opposed to a cued recall task) may have revealed impairment in perceptual processing in older adults, leading to particularly widespread age differences in neural distinctiveness. We additionally provide support for the idea that well-defined reactivation of encoding patterns plays a major role in successful memory retrieval.