The effects of moderate sleep restriction on memory consolidation in a declarative learning task

Description

Here, we examined the effects of moderate sleep restriction (5 hours of sleep for 4 consecutive nights) on a real-life declarative learning task with memory interference, i.e., learning Spanish and complementary Finnish vocabulary.
After an adaptation night (day 1), 15 healthy subjects (6 female) between 18 and 33 years (M= 23.27, SD= 4.30) were randomly assigned to a SLEEP RESTRICTION (n=9, 3 female; 5 hours of sleep for 4 nights) or a CONTROL (n=6; 3 female, no deprivation) group. On day 5, they were asked to learn and retrieve 51 Spanish word-picture associations (SRET1). After sleeping for 5 hours respectively 8 hours, participants completed a second retrieval of the Spanish word-picture associations (SRET2), followed by learning and retrieving (FRET1) Finnish word-picture associations for a subset of 34 of the 51 pictures (i.e, memory interference). Subsequently, they performed another retrieval of the Spanish (SRET3) and Finnish (FRET2) words. On the following two days, all participants slept 8 hours per night. On day 8, participants performed a final retrieval session of Spanish and Finnish vocabulary (SRET4 and FRET3).
After an initial overnight improvement, behavioral results showed a steady deterioration of Spanish retrieval performance in the SLEEP RESTRICTION group (χ²(3) =14.54; p= .002) while there were no significant performance changes in the CONTROL group (i.e., memory stabilization). Regarding sleep parameters, a higher sleep spindle activity (SpA) was associated with stronger memory improvement in both groups at frontal and central sites (rρ=0.697, p= 0.004). Furthermore, better memory retention after interference learning was associated with higher slow oscillation up-state peak amplitudes in both groups (rρ=0.622, p= 0.007).
Our results show that a moderate sleep restriction of 3 hours per night for four consecutive days can have negative effects on memory performance and retention. These memory deficits may be the result of degraded cortical representations during encoding, impaired hippocampal function, and/or reduced capacity for long-term potentiation following sleep restriction. Further, NREM sleep spindle activity and slow oscillations generally facilitated memory consolidation and protected memories from being weakened by interfering information. Thus, our results support earlier findings of sleep spindles and slow oscillations being important contributors to declarative memory consolidation.

Period	9 Jan 2023
Event title	5th Wintersymposium on "Sleep, Cognition and Consciousness"
Event type	Conference
Location	Werfenweng, AustriaShow on map
Degree of Recognition	International