Fear Extinction Memory Is Negatively Associated With Rem Sleep In Insomnia Disorder

Study Objectives: Formation and maintenance of fear-extinction memories are disrupted in post-traumatic stress disorder (PTSD) and anxiety disorders. Sleep contributes to emotional memory consolidation and emotion regulation. Insomnia disorder (ID) is characterized by persistent sleep disturbance as well as rapid eye movement (REM) sleep abnormalities and often precedes or develops in parallel with PTSD and anxiety disorders. Here, we explore the impact of chronic poor sleep and sleep immediately following fear conditioning and extinction learning on preservation of extinction memories.Methods: Twenty-four ID age- and sex-matched to 24 healthy, good sleeper controls (GS) completed up to 2 weeks of habitual sleep monitoring with daily sleep-wake diaries and actigraphy, and then participated in a two-session fear conditioning, extinction learning and extinction recall procedure. Fear Conditioning and Extinction Learning occurred during session 1, followed by Extinction Recall approximately 24 hours later. Skin-conductance responses (SCR) and shock expectancies were recorded throughout all experimental phases to evaluate associative learning and memory. Overnight sleep between sessions 1 and 2 was recorded using ambulatory polysomnography.Results: ID showed greater physiological reactivity during Fear Conditioning. REM sleep physiology was associated with poorer extinction memory in ID but better extinction memory in GS.Conclusion: REM sleep physiology may differentially support emotional memory retention and expression in ID and GS. In the former, REM may enhance retention of fear memories, while in the later, REM may enhance the expression of extinction memories.Statement of SignificanceIncident insomnia disorder exhibits bidirectional risk with incident emotional disorders such as post-traumatic stress disorder (PTSD). Individuals with PTSD show deficits in fear extinction memory. Fear extinction learning and memory are important mechanisms supporting our ability to overcome fears, both in everyday life and during psychotherapies, such as exposure therapy, that treat PTSD. However, to date, evidence is limited as to how insomnia influences fear extinction memory or how intervening sleep, and rapid eye movement (REM) sleep in particular, influence the consolidation of extinction memory. Understanding how REM sleep interacts with fear extinction memory in insomnia may provide a mechanistic link by which those with poor sleep sometimes go on to develop PTSD.