BackgroundSocial anxiety disorder (SAD) is characterized by a significant amount of fear when confronted to social situations. Exposure therapy, which is based on fear extinction, does not often lead to full remission. Here, based on evidence showing that rapid eye movement (REM) sleep promotes the consolidation of extinction memory, we used targeted memory reactivation (TMR) during REM sleep to enhance extinction learning in SAD.MethodsForty-eight subjects with SAD were randomly assigned to two groups: control or TMR group. All patients had two successive exposure therapy sessions in a virtual reality (VR) environment, where they were asked to give a public talk in front of a virtual jury. At the end of each session, and only in the TMR group (N = 24), a sound was paired to the positive feedback phase of therapy (i.e., approval of their performance), which represented the memory to be strengthened during REM sleep. All participants slept at home with a wearable headband device which automatically identified sleep stages and administered the sound during REM sleep. Participants' anxiety level was assessed using measures of parasympathetic (root mean square of successive differences between normal heartbeats, RMSSD) and sympathetic (non-specific skin conductance responses, ns-SCRs) activity, and subjective measures (Subjective Units of Distress Scale, SUDS), during the preparation phase of their talks before (T1) and after (T2) one full-night's sleep and after 1 week at home (T3). Participants also filled in a dream diary.ResultsWe observed an effect of time on subjective measures of anxiety (SUDS). We did not find any difference in the anxiety levels of the two groups after 1 week of TMR at home. Importantly, the longer the total duration of REM sleep and the more stimulations the TMR group had at home, the less anxious (increased RMSSD) these participants were. Finally, fear in dreams correlated positively with ns-SCRs and SUDS at T3 in the TMR group.ConclusionTMR during REM sleep did not significantly modulate the beneficial effect of therapy on subjective anxiety. Yet, our results support that REM sleep can contribute to extinction processes and substantiate strong links between emotions in dreams and waking stress levels in these patients.

The function of dreams is a longstanding scientific research question. Simulation theories of dream function, which are based on the premise that dreams represent evolutionary past selective pressures and fitness improvement through modified states of consciousness, have yet to be tested in cross-cultural populations that include small-scale forager societies. Here, we analyze dream content with cross-cultural comparisons between the BaYaka and Hadza foraging groups and Global North populations, to test the hypothesis that dreams in forager groups serve a more effective emotion regulation function due to their strong social norms and high interpersonal support. Using a linear mixed effects model we analyzed 896 dreams from 235 individuals across these populations, recorded using sleep diaries and the Most Recent Dream survey method. Dream texts were processed into four super-categories psychosocial constructs using the LIWC-22 dictionary. The BaYaka displayed greater community-oriented dream content. Both the BaYaka and Hadza exhibited heightened threat dream content, while, at the same time, the Hadza demonstrated low negative emotions in their dreams. The Global North Nightmare Disorder group had increased negative emotion content, and the Canadian student sample during the COVID-19 pandemic displayed the highest anxiety dream content. In conclusion, this study supports the notion that dreams in non-clinical populations can effectively regulate emotions by linking potential threats with non-fearful contexts, reducing anxiety and negative emotions through emotional release or catharsis. Overall, this work contributes to our understanding of the evolutionary significance of this altered state of consciousness.

BackgroundSocial anxiety disorder (SAD) is an anxiety disorder characterized by a significant amount of fear when confronted to social situations and can cause considerable distress in daily life. Exposure therapy, which is based on fear extinction, is a popular and effective treatment for SAD, although it does not often lead to full remission. Here, we aimed at improving exposure therapy outcome. Specifically, based on previous research showing that rapid eye movement (REM) sleep promotes the consolidation of extinction memory, we used targeted memory reactivation (TMR) during REM sleep to enhance extinction learning.Methods48 subjects (32 women and 16 men, mean age of 24.41 ± 4.91) with moderate or severe SAD according to DSM-5 participated in our study, and were randomly assigned to one of two matched groups: control or TMR group. All patients had two successive exposure therapy sessions in a virtual reality (VR) environment, where they were asked to give a public talk in front of a virtual jury. At the end of each session, and only in the TMR group (N=24), a sound was paired to the positive feedback phase of exposure therapy (i.e. approval of their performance), and which represents the extinction memory to be strengthened during REM sleep. All participants slept at home with a wearable headband device which automatically identified sleep stages online and administered the sound several times during REM sleep. Anxiety level was assessed using measures of sympathetic (electrodermal activity component : non-specific skin conductance responses, ns-SCRs) and parasympathetic (heart rate variability component : root mean square of successive differences between normal heartbeats, RMSSD) activity, and subjective measures (Subjective Units of Distress Scale, SUDS), during the preparation phase of their virtual talks before (T1) and after (T2) one full-night’s sleep with auditory stimulation and after one week of auditory stimulation at home (T3). Participants also filled in a dream diary one week prior and one week after the day of exposure therapy.ResultsSubjective anxiety was reduced during the second and third anticipatory preparation phase of exposure, compared to the first one, for both groups (p < 0.001). RMSSD levels were lower in the TMR group compared to the control group (p=.037) during the preparation phase after 8 nights of stimulation at home (T3). No significant result between groups was observed for SUDS and the ns-SCRs at T3. Importantly, the longer REM sleep and the more stimulations the TMR group (but not the control group) had at home, the less anxious (increased RMSSD) these participants were. Finally, fear in dreams correlated positively with measures of stress (ns-SCRs and SUDS) in this group.ConclusionsTMR during REM sleep did not modulate the beneficial effect of exposure therapy on anxiety-related distress (SUDS). Yet, our results support that REM sleep can contribute to extinction processes and substantiate strong links between emotional experiences in dreams and waking stress levels in these patients.