REM Sleep, Safety Signal Learning, and Extinction Processes in Posttraumatic Stress Disorder
Posttraumatic Stress Disorder (PTSD) is associated with a number of negative physical and mental health consequences. Fear conditioning plays an important mechanistic role in PTSD, and PTSD patients also show deficits in safety signal learning. Sleep, particularly REM sleep, serves an important role in safety learning and extinction processes in animal models and healthy humans. Nothing is known about the link between REM sleep and safety signal learning or extinction memory in clinical populations.
This study examined the relationship between REM sleep, safety signal learning, and extinction processes in veterans with PTSD (n = 13). Patients’ overnight sleep was characterized in the lab via polysomnography (PSG). The next day, participants underwent a fear conditioning paradigm during which they acquired fear toward a visual cue. This testing session also included a visual cue that became a safety signal (CS-). Following this, the veterans’ sleep was monitored overnight again, after which they underwent an extinction learning session. Following a third night of sleep, extinction recall was tested. Bivariate correlations examined the relationship between the slope of safety signal learning and subsequent REM sleep consolidation, as well as the relationship between REM sleep consolidation and subsequent extinction recall on the last day of testing.
Results suggest veterans learned to differentiate the CS+ and the CS- on the first day of testing. Veterans who underwent safety learning more quickly on the first day of testing showed more efficient REM sleep that night (r = .607, p = .028). On the second day of testing, the patients successfully underwent extinction learning. Patients with a higher percentage of REM sleep on the last night of the study showed less anxious responding to the CS- early on the last day of testing (r = .688, p = .009).
PTSD patients who demonstrated better safety learning showed more consolidated REM sleep, which in turn was associated with better subsequent safety re-learning. These results provide additional evidence suggesting REM sleep plays a mechanistic role in the maintenance of PTSD and thus identify a modifiable biological process to target in treatment of PTSD.