# Targeted memory reactivation during REM sleep may selectively enhance the late positive potential amplitude in previously encountered negative images: preliminary findings

## TL;DR

This study suggests that reactivating memories during REM sleep with odors may enhance brain responses to previously seen negative images.

## Contribution

It is the first to show that TMR during REM sleep may selectively enhance LPP amplitude for negative images.

## Key findings

- TMR increased LPP amplitude for negative old images between 500 and 800 ms after image onset.
- No changes in LPP were observed for negative new images or neutral/positive images.
- TMR did not affect memory performance, arousal, or emotional valence after viewing images.

## Abstract

The function of rapid eye movement (REM) sleep in consolidating emotional memories and reducing emotional charge has been studied, but evidence remains conflicting. Our study employed the targeted memory reactivation (TMR) technique, which posits that specific sleep memories can be reactivated through sensory stimuli during sleep. Additionally, the late positive potential (LPP), a component of event-related brain potentials, was measured while participants (N = 16, 22.5 ± 1.2 years) viewed negative, neutral, or positive images (old images) paired with an odor stimulus. During subsequent REM sleep, the same odor was presented in the TMR condition, while an odorless stimulus was presented in the control condition. Upon awakening, participants performed the same task as before sleep, with new images added to test memory. The results demonstrated that TMR increased the LPP amplitude between 500 and 800 ms after image onset following sleep for negative old images; however, no changes were observed in the LPP in the same range for negative new images and neutral or positive images. TMR during REM sleep did not influence performance on the memory task, nor did it affect levels of arousal or emotional valence immediately after viewing the emotional images. These preliminary findings from our pilot study suggest that either the presentation of phenylethyl alcohol itself or the reprocessing induced by TMR during REM sleep selectively enhances the LPP in emotional processing of previously encountered negative stimuli. Due to the small sample size of this study, further investigation is warranted to evaluate the robustness of the results.