Abstract
Both stress and sleep enhance emotional memory. They also interact, with the largest effect of sleep on emotional memory being seen when stress occurs shortly before or after encoding. Slow wave sleep (SWS) is critical for long-term episodic memory, facilitated by the temporal coupling of slow oscillations and sleep spindles. Prior work in humans has shown these associations for neutral information in non-stressed participants. Whether coupling interacts with stress to facilitate emotional memory formation is unknown. Here, we addressed this question by reanalyzing an existing dataset of 64 individuals. Participants underwent a psychosocial stressor (32) or comparable control (32) prior to the encoding of 150-line drawings of neutral, positive, and negative images. All participants slept overnight with polysomnography, before being given a surprise memory test the following day. In the stress group, time spent in SWS was positively correlated with memory for images of all valences. Results were driven by those who showed a high cortisol response to the stressor, compared to low responders. The amount of slow oscillation-spindle coupling during SWS was negatively associated with neutral and emotional memory in the stress group only. The association with emotional memory was significantly stronger than for neutral memory within the stress group. These results suggest that stress around the time of initial memory formation impacts the relationship between slow wave sleep and memory.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
Data were collected at institution 3. All data were analyzed at institution 1.
Manuscript revised based on reviewer comments. Key changes: 1. Additional analyses of SO-spindle coupling 2. Suplementary analyses of spindles/slow oscillations in isolation
Abbreviations
- EEG
- Electroencephalography
- FDR
- False discovery rate
- fMRI
- Functional magnetic resonance imaging
- IAPS
- International Affective Picture System
- PSG
- Polysomnography
- PFC
- Pre-frontal cortex
- REM
- Rapid eye movement
- SWS
- Slow wave sleep
- TSST
- Trier Social Stress Test