Available online 21 July 2022, 107662

Sleep characteristics and physiological arousal during testing tasks were recorded.

A short afternoon nap contributed to procedural but not declarative memory.

Both sleep characteristics and physiology would contribute to memory consolidation.

Task difficulty would moderate the relationship between task performance and EEGs.

The relationship between sleep and memory consolidation has not been fully revealed. The current study aimed to investigate how a brief afternoon nap contributed to the consolidation of declarative and procedural memory by exploring the relationship between sleep characteristics (i.e., the durations of sleep stages and slow oscillation, slow-wave activity, and spindle activity extracted from sleep) and task performance and the relationship between delta, theta, alpha, and beta bands extracted from wake during task performance and task performance. Twenty-three healthy young adults were recruited to learn a paired associates learning task and a sequential finger-tapping task with easy and difficult levels and be tested for memory performance before and after the intervention (i.e., an about 30-min nap or stay awake). Electroencephalogram (EEG) signals were recorded during the whole experiment. Results revealed that a short afternoon nap improved movement speed for the procedural memory task, regardless of the task difficulty, but unaffected the performance on the declarative memory task. Besides, the improvement in movement speed for the easy procedural memory task was positively correlated with slow-wave activity (SWA) during non-rapid-eye-movement (NREM) sleep but negatively correlated with slow oscillation and spindle activity during sleep stage 2 and NREM sleep, and the improvement in the difficult procedural memory task correlated positively with SWA during NREM sleep. Moreover, performance on the easy declarative and procedural memory tasks was negatively correlated with the relative power of alpha or theta; whereas the alpha band was positively correlated with the difficult declarative memory performance. These findings suggested that a brief afternoon nap with NREM sleep would benefit procedural memory consolidation but not declarative memory; such contribution of napping to memory consolidation would be either explained by the sleep characteristics or physiological arousal during performing tasks; task difficulty would moderate the relationship between performance on the declarative memory task and EEGs during task performance.

nap

declarative memory

procedural memory

difficulty level

EEG

© 2022 Published by Elsevier Inc.