Emotional Enhancement of Memory in Alzheimer’s Disease: A Systematic Review

Abstract

AbstractBackgroundProgressive decline in episodic memory is a hallmark of Alzheimer’s disease (AD). Emotional arousal is known to enhance memory. The amygdala, locus coeruleus, hippocampus, and other regions, are key brain structures involved in the facilitation of memory through emotions. Amygdala‐mediated enhanced encoding of emotionally arousing stimuli or events may improve memory in AD patients, however whether this effect is present in patients with AD remains unclear.MethodA systematic search of the literature was conducted in accordance with PRISMA guidelines to identify relevant literature on emotional enhancement of memory (EEM) in AD. We utilized MEDLINE and PsycInfo. Search terms related to emotional memory and Alzheimer’s were searched as keywords and mapped to medical subject headings.Result1545 studies were screened; 40 were included. Participant age ranged from 64 to 84 years. Sample sizes ranged from 20 to 126. Only 11 of the 40 (27.5%) included brain MRI and evaluation of amygdala volume. 34 studies examined long‐term memory. Results showed that 12 out of 34 studies (35.3%) showed clear EEM for long‐term memory among participant with AD. A further 10 studies (29.4%) found that EEM was influenced by stimuli type, valence of emotion, level of encoding, or intensity of emotion. Yet 12 studies (35.3%) found no effect of EEM in AD. Of the 6 studies that specifically explored flashbulb memories in AD, 3 found no EEM and 3 observed that the effect was content‐dependent, such that personal details were remembered more often than factual details of events.ConclusionStudies which included brain imaging showed that amygdala volume is the strongest predictor of EEM in AD, regardless of level of cognitive impairment. The conflicting literature on EEM in AD reveals the importance of evaluating volumes or networks of brain regions known to be involved in emotional memory processing. AD patients included in these studies likely had varying degrees of atrophy in the amygdala, locus coeruleus, hippocampus and frontal regions involved in modulating emotional memories. However, without confirmation from brain imaging, the integrity of these brain structures cannot be established. Future studies are needed to confirm whether atrophy of important brain regions diminishes EEM in AD.