The effect of REM-sleep disruption on affective processing: A systematic review of human and animal experimental studies.

Evidence on the importance of rapid-eye-movement sleep (REMS) in processing emotions is accumulating. The focus of this systematic review is the outcomes of experimental REMS deprivation (REMSD), which is the most common method in animal models and human studies on REMSD. This review revealed that variations in the applied REMSD methods were substantial. Animal models used longer deprivation protocols compared with studies in humans, which mostly reported acute deprivation effects after one night. Studies on animal models showed that REMSD causes aggressive behavior, increased pain sensitivity, reduced sexual behavior, and compromised consolidation of fear memories. Animal models also revealed that REMSD during critical developmental periods elicits lasting consequences on affective-related behavior. The few human studies revealed increases in pain sensitivity and suggest stronger consolidation of emotional memories after REMSD. As pharmacological interventions (such as selective serotonin reuptake inhibitors [SSRIs]) may suppress REMS for long periods, there is a clear gap in knowledge regarding the effects and mechanisms of chronic REMS suppression in humans.

REM Sleep Preserves Affective Response to Social Stress-Experimental Study.

Sleep's contribution to affective regulation is insufficiently understood. Previous human research has focused on memorizing or rating affective pictures and less on physiological affective responsivity. This may result in overlapping definitions of affective and declarative memories and inconsistent deductions for how rapid eye movement sleep (REMS) and slow-wave sleep (SWS) are involved. Literature associates REMS theta (4-8 Hz) activity with emotional memory processing, but its contribution to social stress habituation is unknown. Applying selective sleep stage suppression and oscillatory analyses, we investigated how sleep modulated affective adaptation toward social stress and retention of neutral declarative memories. Native Finnish participants (N = 29; age, M = 25.8 years) were allocated to REMS or SWS suppression conditions. We measured physiological (skin conductance response, SCR) and subjective stress response and declarative memory retrieval thrice: before laboratory night, the next morning, and after 3 d. Linear mixed models were applied to test the effects of condition and sleep parameters on emotional responsivity and memory retrieval. Greater overnight increase in SCR toward the stressor emerged after suppressed SWS (intact REMS) relative to suppressed REMS (20.1% vs 6.1%; p = 0.016). The overnight SCR increase was positively associated with accumulated REMS theta energy irrespective of the condition (r = 0.601; p = 0.002). Subjectively rated affective response and declarative memory recall were comparable between the conditions. The contributions of REMS and SWS to habituation of social stress are distinct. REMS theta activity proposedly facilitates the consolidation of autonomic affective responses. Declarative memory consolidation may not have greater dependence on intact SWS relative to intact REMS.

Does sleep promote adaptation to acute stress: An experimental study.

Objectives: Evidence of the impact of chronic stress on sleep is abundant, yet experimental sleep studies with a focus on acute stress are scarce and the results are mixed. Our study aimed to fill this gap by experimentally investigating the effects of pre-sleep social stress on sleep dynamics during the subsequent night, as measured with polysomnography (PSG). Methods: Thirty-four healthy individuals (65% females, Mage = 25.76 years SD = 3.35) underwent a stress-inducing (SC) or neutral control condition (CC) in virtual reality (VR). We used overnight EEG measurements to analyze the basic sleep parameters and power spectral density (PSD) across the sleep cycles, and measured heart rate and its variability (HRV), skin electrodermal activity (EDA), and salivary cortisol to capture physiological arousal during the VR task and the pre-sleep period. Results: Following acute stress (SC), the amount of slow-wave sleep (SWS) was higher and N2 sleep lower relative to CC, specifically in the first sleep cycle. In SC, PSD was elevated in the beta-low (16-24 Hz) and beta-high (25-35 Hz) frequency ranges during both stages N2 and SWS over the entire night. Conclusions: Sleep promoted adaptation to acute social stress by a longer duration of SWS in the subsequent sleep period, especially in early sleep. A similar homeostatic effect towards restorative sleep is well-evidenced in animal model stress studies but has not been previously reported in experimental human studies. Whether the high-frequency PSD activity during stages N2 and SWS also serves in the resolution of transient stress, remains open.

Temporal pathways between circadian rhythm, depression and anxiety in the transition from adolescence to early adulthood.

BACKGROUND: Sleep and circadian rhythm problems intertwine with affective disorders. Adolescents are particularly vulnerable to developing sleep and affective problems. Yet, the temporal pathways between circadian rhythm, depression and anxiety in the transition phase from adolescence to early adulthood are not fully understood. METHODS: 233 adolescents (76 % females) participated at two time points (T1 and T2) at an interval of 19-months (aged 16.8 and 18.4 years). We used The Beck Depression Inventory-II, Generalized Anxiety Disorder Assessment, GENEActiv actigraphy across 8 days (delayed sleep phase (DSP), sleep duration, midpoint, and regularity), and iButton 1922L thermologgers across 3 days (intrinsic circadian period length, amplitude, and mesor). RESULTS: A shorter sleep duration at T1 associated with an increase in affective problems at T2, and affective problems at T1 associated with an increase in sleep irregularity at T2. A longer circadian period at T1 associated with an increase in males' affective problems at T2. Moderate to severe depression and anxiety at T1 associated with a 2.69-fold risk (95 % CI 1.38-5.26, p = 0.004) and 2.11-fold risk (95 % CI 1.04-4.25, p = 0.038) of poor sleep quality at T2. Moderate to severe generalized anxiety associated with a 3.17-fold risk (95 % CI 1.35-7.41, p = 0.008) of DSP at T2. LIMITATIONS: The follow-up period is short. CONCLUSIONS: The results revealed bidirectional temporal links between sleep and affective problems. Novel observations include a heightened risk of future DSP following a current anxiety disorder and a heightened risk of affective problems following a longer circadian period measured from the 24-hour temperature variation in males.