Vagal activity in REM sleep is associated with extinction recall in trauma exposed individuals but not in individuals with post-traumatic stress disorder

Lauren Watford, BA

McLean Hospital – Research Assistant
WATFORD_LAUREN poster

Scientific Abstract

Background: Post-traumatic stress disorder (PTSD) is characterized by impaired fear extinction memory. Sleep facilitates consolidation of fear extinction, and 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, vagal activity during sleep is reduced 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 and trauma exposed controls (TEC). 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 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: In TEC, extinction recall was significantly correlated with REM HRV measures that reflect vagal activity, including high frequency (HF) absolute power (Rs=0.51, p =0.009) and HF normalized units (Rs=0.54, p =0.005). In hierarchical regression models with extinction recall as the outcome, HF HRV 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.

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research Areas

Authors

Lauren Watford, B.A., Cagri Yuksel, MD, Augustus Kram Mendelsohn, B.A., Katelyn I. Oliver, B.A., Abegail Vidrin, Uriel Martinez, Edward F. Pace-Schott, PhD.

Principal Investigator

Edward F. Pace-Schott, PhD