The Contribution of Previous Information to Current Memory Processing: Comparisons Between Older Adults with Mild Cognitive Impairment and Normal Elderly

Numerous studies have found that previous information can affect the current explicit working memory processing. However, the study that investigate the effect of previous episodes on the implicit working memory processing has been limited. The present study investigated this issue in healthy older adults and patients with mild cognitive impairment (MCI). A hybrid delayed-match-to-sample task was used to examine the implicit working memory processing regardless of explicit memory components. Functional magnetic resonance imaging data was collected. The behavioral results demonstrated that the previously studied information was able to facilitate the following implicit working memory processing. Nevertheless, this effect was impaired in MCI patients, although both healthy older adults and MCI patients have shown significant implicit working memory processing. Whole-brain activation analysis revealed that there were significant interactions between group and previous information (Studied and Non-studied) in the left cuneus. The psychophysiological-interaction analysis showed that the functional connectivity between left cuneus and regions in bilateral middle occipital gyrus as well as dorsal regions of left precuneus was modulated by previous episodic information in healthy older adults. However, no significant region was found in MCI patients. The current study for the first time revealed that the previous episodic information can facilitate the following implicit working memory procession in healthy older adults, and demonstrated the key cortical structure and cortical pathways underlying the interactions between previous episodic information and current implicit working memory processing.