Sleep preferentially modulates the affective tone of memories encoded closer to sleep onset, independent of recognition accuracy, suggesting a dissociation between mnemonic and affective consolidation.
Key Findings
Results
Sleep led to more positive cue ratings in the negative-to-positive condition compared to wake controls.
120 participants were randomly assigned to sleep or wake groups
Participants completed both positive-to-negative and negative-to-positive conditions in counterbalanced order
Emotional valence ratings were collected immediately after encoding and after a 12-hour interval (overnight sleep vs. daytime wakefulness)
The negative-to-positive condition involved cues first paired with negative pictures, then later paired with positive pictures
Results
Sleep led to more negative cue ratings in the positive-to-negative condition compared to wake controls.
The positive-to-negative condition involved cues first paired with positive pictures, then later paired with negative pictures
This finding mirrors the negative-to-positive result, indicating sleep biases emotional memory toward the most recently encoded valence
Both conditions used pseudoword-picture associations where the same cues were paired with emotional pictures of opposite valence
Results
Stronger positive picture ratings predicted greater positive-valence shifts after sleep in the negative-to-positive condition.
This relationship was specific to the sleep group in the negative-to-positive condition
The finding suggests that the initial emotional intensity of the most recently encoded experience modulates the degree of sleep-related affective consolidation
This predictive relationship was observed at the level of individual emotional picture ratings
Results
Sleep's modulation of emotional memory valence was independent of recognition accuracy.
The study found a dissociation between mnemonic and affective consolidation
Sleep selectively biased emotional value according to the temporal order of experience without a corresponding difference in recognition accuracy
This suggests that affective and mnemonic aspects of memory consolidation during sleep can operate independently
Results
Sleep preferentially consolidates emotional memories encoded closer to sleep onset, modulating the affective tone based on temporal proximity.
In both opposing-valence sequences, sleep enhanced the emotional valence of the most recently encoded (i.e., temporally proximal to sleep) experience
This pattern held across both positive-to-negative and negative-to-positive orderings
The authors interpret this as evidence that 'sleep selectively biases emotional value according to the temporal order of experience'
The principle is proposed to be independent of emotional direction (positive or negative)
What This Means
This research suggests that sleep plays a selective role in shaping how we emotionally remember experiences, particularly favoring the most recent emotional experience before sleep. In this study, participants learned associations between made-up words and emotionally charged pictures, where each word was first paired with one type of emotional image (e.g., negative) and later with an image of the opposite emotion (e.g., positive). After a 12-hour period of either overnight sleep or daytime wakefulness, those who slept showed stronger emotional memory shifts toward whichever emotion was encountered most recently — more positive feelings when the positive experience came last, and more negative feelings when the negative experience came last.
Importantly, this emotional bias from sleep was not explained by better or worse memory for the images themselves — people remembered the pictures at similar rates regardless of whether they slept or stayed awake. This points to a separation between remembering the facts of an experience and how you feel about it, with sleep specifically influencing the emotional coloring of memories. Additionally, the more strongly positive the final pictures were rated, the greater the positive emotional shift after sleep.
This research suggests that the timing of emotional experiences relative to sleep may matter for how those experiences are ultimately remembered emotionally. The authors note this principle could potentially inform therapeutic approaches — for example, timing positive experiences close to sleep to optimize emotional outcomes — though they emphasize that clinical applications require further investigation.
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Tsang Y, Xia T, Leung W, Hu X. (2026). Temporal proximity to sleep determines emotional memory interference.. Learning & memory (Cold Spring Harbor, N.Y.). https://doi.org/10.1101/lm.054156.125