Impaired emotional memory dissipation in insomnia disorder

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.

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.

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.

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.