Abstract
Introduction
It is widely accepted that “offline” processes during sleep contributes to memory. Working Memory (WM) capacity, which reflects “online” memory processing, is an important factor influencing cognitive functioning, which declines with age. In younger individuals, a positive association is reported between WM-capacity and declarative memory improvement.
Methods
We examined the relation between WM and long-term memory consolidation, among younger [N=105, 18-25yr] and older adults (N=119, 60-85yr). Subjects completed an OSPAN WM task, encoded a Word-Paired Association (WPA) task in the morning (Test1), and were tested on the WPA in the afternoon (Test2) after a 90-minute polysomnographically-recorded nap or wake. Half of the subjects were exposed to negatively valenced word-pairs (EWPA) while the other half were exposed to neutral word-pairs (NWPA). Subjects rated valence of the word-pairs at Test1 and Test2. We compared the four groups (young-EWPA, young-NWPA, old-EWPA and old-NWPA) on WM and WPA in both wake and sleep.
Results
In both wake and sleep, in the WPA, ageXword-condition interaction was found (p=.004). Post-hoc analysis revealed that in wake, younger-EWPA had higher performance (p=.03) than younger-NWPA, however, older-EWPA had lower performance (p=.03) than older-NWPA. Additionally, we found an ageXword-condition interaction whereby youngers showed no change in ratings, while older adults rated word-pairs more positively both in wake (p=.03) and sleep (p=.002) at Test 2. Youngers had higher WM performance (p=.007), also their WM performance was positively associated with WPA both for Neutral (p=.03) and Emotional (p=.01). WM and WPA among older adults was not related. In younger-EWPA, Stage2-sleep-minutes was positively associated to WPA improvement (p=.03) where this association was negative among older-EWPA (p=.02). In older-NWPA, Stage2-sleep-minutes was positively associated with WPA (p=.004).
Conclusion
Our findings indicate an association between WM and emotionally-salient memory formation that is modulated by age. Older adults, but not younger, showed the emotional bias previously reported. WM was higher in younger adults related to memory improvement. Stage2-sleep was related to memory improvement in both groups, but in opposite directions. In sum, the role of sleep in memory consolidation changes with aging and WM may play a role in this process.
Support
Fenn et al.,2012
Effects of a chattering teeth training oral appliance for working memory improvement in healthy volunteers: a cross-over randomized trial
