VAGAL ACTIVITY IN REM SLEEP IS ASSOCIATED WITH EXTINCTION RECALL IN TRAUMA EXPOSED INDIVIDUALS BUT NOT IN INDIVIDUALS WITH POST-TRAUMATIC STRESS DISORDER

Abstract Introduction Post-traumatic stress disorder (PTSD) is characterized by impaired fear extinction memory. Sleep, and especially REM sleep, facilitates consolidation of fear extinction. Therefore, it is postulated that abnormal sleep physiology in PTSD may contribute to its persistence. Recent studies suggest that vagal activity may support the memory benefit of sleep. In addition, a separate line of studies shows reduced vagal activity during sleep in PTSD. However, the link between extinction memory and vagal activity during sleep has not been investigated in PTSD. We examined the association of extinction recall with vagal activity, measured as heart rate variability (HRV), during REM sleep, in PTSD and matched controls. Methods Participants included individuals with PTSD (n=70) and trauma exposed controls (TEC; n=69). All participants completed 3 nights of ambulatory polysomnography that included ECG. After acclimation and baseline PSG nights, fear conditioning and extinction learning were carried out in the evening after which they completed a third ("consolidation") PSG night. Extinction recall was tested 24h later. During fear conditioning, partial reinforcement with a mild electric shock produced a conditioned skin conductance response (SCR) to the image of a colored lamp, which was immediately extinguished by un-reinforced presentations in a different room. Extinction recall was indexed by the degree to which SCR remained suppressed 24h later. HRV indices were calculated using Kubios software. Results Preliminary analyses included 20 individuals with PTSD and 37 TEC participants. In the TEC group, extinction recall was significantly correlated with REM sleep HRV measures that reflect vagal activity, including high frequency (HF) absolute power (Rs=0.51, p =0.009), HF normalized units (Rs=0.54, p =0.005) and RMSSD (Rs=0.40, p =0.046). In hierarchical regression models which included extinction recall as the dependent variable, HF absolute power accounted for a significant proportion of the variance, over and above a model that included %REM sleep, %N3 sleep, REM density and average duration of REM epochs (R2=0.50, F=5.06, p=0.04). These associations were not present in the PTSD group Conclusion Our preliminary results suggest that vagal activity during REM sleep is involved in the consolidation of extinction memory and that this mechanism may be impaired in PTSD. Support (If Any) R01MH109638 K23MH119322