Impaired emotional memory dissipation in insomnia disorder.

Background: Insomnia disorder, characterized by chronic sleep disruption, often co-occurs with maladaptive emotional memory processing. However, much remains unknown regarding the evolution of emotional memories and their neural representations over time among individuals with insomnia disorder.

Method: We examined the electroencephalographic (EEG) activities during emotional memory encoding, post-encoding sleep, and multiple retrieval phases - including immediate post-encoding, post-sleep, and a 7-day delayed retrieval - among 34 participants with insomnia disorder and 35 healthy control participants.

Results: Healthy controls exhibited adaptive dissipation of emotional memory: memory declined over time, accompanied by reduced subjective feelings toward negative memories. In contrast, participants with insomnia exhibited impaired dissipation: they retained both the emotional content and affective tone of the memories, with diminished time-dependent declines in memory and affect. Beyond behavioral performance, only participants with insomnia maintained stable neural representations of emotion over time, a pattern absent in healthy controls. Additionally, during the post-encoding sleep, slow-wave sleep (SWS), and rapid eye movement (REM) sleep durations predicted the adaptive dissipation of emotional memory over time, but only among healthy participants.

Conclusion: These findings highlight abnormalities in emotional memory processing among individuals with insomnia disorder and underscore the important function of SWS and REM sleep in facilitating adaptive emotional memory processing.