When we update our episodic memories with new information, mnemonic competition between old and new memories may result because of the presence of shared features. Behavioral studies suggest that this competition can lead to proactive interference, resulting in unsuccessful memory updating, particularly for older adults. It is difficult with behavioral data alone to measure the reactivation of old, overlapping memories during retrieval and its impact on memory for new memories. Here, we applied encoding–retrieval representational similarity (ERS) analysis to EEG data to estimate event-specific encoding-related neural reinstatement of old associations during the retrieval of new ones and its impact on memory for new associations in young and older adults. Our results showed that older adults' new associative memory performance was more negatively impacted by proactive interference from old memories than that of young adults. In both age groups, ERS for old associative memories was greater for trials for which new associative memories were forgotten than remembered. In contrast, ERS for new associative memories was greater when they were remembered than forgotten. In addition, older adults showed relatively attenuated target (i.e., new associates) and lure (i.e., old associates) ERS effects compared to younger adults. Collectively, these results suggest that the neural reinstatement of interfering memories during retrieval contributes to proactive interference across age, whereas overall attenuated ERS effect in older adults might reflect their reduced memory fidelity.

Some prior research has found that older adults are more susceptible to proactive interference than young adults. The current study investigated whether age-related deficits in pFC-mediated cognitive control processes that act to detect and resolve interference underlie increased susceptibility to proactive interference in an associative memory task. Young and older adults were scanned while tasked with remembering which associate (face or scene) objects were paired with most recently during study, under conditions of high, low, or no proactive interference. After scanning, participants' memory was tested for varying levels of episodic detail about the pairings (i.e., target category vs. specific target category vs. specific target associate). Young and older adults were similarly susceptible to proactive interference. Memory for both the general target category and the specific target associate worsened as the level of proactive interference increased, with no robust age differences. For both young and older adults, the left ventrolateral pFC, which has been indicated in controlled retrieval of goal-relevant conceptual representations, was sensitive to increasing levels of interference during encoding but was insensitive to associative memory accuracy. Consistent with the Compensation-Related Utilization of Neural Circuits Hypothesis model of cognitive aging, the ventromedial pFC, which is involved in the monitoring of internally generated information, was recruited more by older than young adults to support the successful retrieval of target–object pairs at lower levels of proactive interference. Collectively, these results suggest that some older adults are able to engage in the cognitive control processes necessary to resolve proactive interference to the same extent as young adults.