Does sleep change the emotional bias in memory in older adults?

Abstract

Sleep supports the consolidation of emotional memories. Young adults exhibit a bias towards consolidation of negative memories during sleep while older adults exhibit a bias towards consolidation of positive memories, which parallels known biases in emotional memory encoding. Yet it is unclear whether biases found after sleep are carried over from biases in encoding or if sleep amplifies or changes the emotional memory biases as prior studies did not include a measure of memory before the sleep/wake interval. The present study assessed emotional memory before and after intervals of sleep and wake to determine whether sleep biases the selectivity of emotional memory. Healthy young (N = 49) and older adults (N = 50) completed both a positive and negative emotional memory task. Emotional images were viewed, followed by an immediate recognition assessment before overnight sleep (Sleep group; YA = 27, OA = 29) or before a day awake (Wake group; YA = 22, OA = 21). Delayed recognition was assessed approximately 12-hrs later. Results indicate no emotional bias at encoding. After the 12-hr delay there was a significant interaction between the effects of condition (positive vs. negative) and group (Sleep vs. Wake) such that sleep (relative to wake) benefitted negative but not positive memories in both young and older adults. These findings suggest that sleep may selectively enhance negative emotional memory consolidation, consistent with prior findings in young adults but contradicting the expected shift toward positive memory consolidation previously reported in older adults. Despite age-related changes in sleep and memory, sleep-dependent negative emotional memory may be preserved in some older adult samples.