The impact of sleep on factual memory retention over 24 hr.

Although a period of sleep seems to benefit the retention of declarative memories, recent studies have challenged both the size of this effect and its active influence on memory consolidation. This study aimed to further investigate the effect of sleep and its time dependency on the consolidation of factual information. In a within-subjects design, 48 participants (Mage = 24.37 ± 4.18 years, 31F) were asked to learn several facts in a multi-sensory "flashcard-like" memory task at 21:00 hours (sleep first condition) or at 09:00 hours (wake first condition). Then, in each condition, participants performed an immediate recall test (T0), and two delayed tests 12 hr (T1) and 24 hr (T2) later. Participants' sleep was recorded at their homes with a portable device. Results revealed that memory retention was better after a night of sleep compared with wakefulness, regardless of the delay from encoding (a few hr versus 12+ hr), but the sleep effect was modest. The decline in memory during the wake period following sleep was smaller compared with the decline observed during the 12 hr of wakefulness after encoding. However, after 24 hr from the encoding, when all participants experienced a period of both sleep and wakefulness, memory performance in the two conditions was similar. Overall, our data suggest that sleep exerts a small, yet beneficial, influence on memory retention by likely reducing interference and actively stabilizing memory traces.

False memories formation after a retention period spent asleep or awake in individuals with insomnia and good sleepers: a polysomnographic study.

False memories are a possible by-product of sleep-related memory consolidation processes when delayed testing is performed after a retention interval spent asleep. To date, the effect of a retention period spent asleep or awake on false memories formation has been addressed only in healthy subjects, while neglecting sleep-disordered populations. In the present study, we investigated this effect in 17 insomniacs and 15 good sleepers through the Deese-Roediger-McDermott paradigm. In both groups, the encoding phase was followed by an 8-h retention period spent in polysomnography monitored sleep (S-condition) or wake (WK-condition). We observed that, at free recall, insomniacs produced more false recalls in the WK-condition compared to the S-condition, whereas the good sleepers showed more false recalls in S-condition than in the WK-condition. Moreover, false recalls were higher in good sleepers than in insomniacs in the S-condition. Both groups produced more veridical recalls in the S-condition than in the WK-condition. For recognition, hits (correctly recognised words) were more numerous in the S-condition than in the WK-condition. Our results confirm previous data on sleep-related false memories production in good sleepers. Additionally, they show that, in insomniacs, false memories production is reduced after a sleep relative to remaining awake. These data suggest that false memories formation, reflecting adaptive memory reshaping processes going on during sleep, could occur at awakening as long as the sleep episode is efficient enough. A notable methodological issue was also identified, in that the Deese-Roediger-McDermott paradigm can be useful to investigate sleep-dependent memory processes for false memories only when a more cognitively demanding task is employed (i.e., free-recall instead of recognition tasks).

Psychophysiological stress influences temporal accuracy.

Distortions of duration perception are often observed in response to highly arousing stimuli, but the exact mechanisms that evoke these variations are still under debate. Here, we investigate the effect of induced physiological arousal on time perception. Thirty-eight university students (22.89 ± 2.5; 28 females) were tested with spontaneous finger-tapping tasks and a time bisection task (with stimuli between 300 and 900 ms). Before the time bisection task, half of the participants (STRESS group) performed a stress-inducing task, i.e., the Paced Auditory Serial Addition Test (PASAT), whereas the other participants (CONTROL group) performed a control task, the Paced Auditory Number Reading Task (PANRAT). The PASAT induced a greater heart rate, but not electrodermal, increase, as well as a more unpleasant and arousing state compared to the PANRAT. Moreover, although the two groups presented a similar performance at the finger-tapping tasks, participants in the STRESS group showed better temporal performance at the time bisection task (i.e., lower constant error) than the controls. These results indicate that psychophysiological stress may alter the subsequent perception of time.

The role of sleep and wakefulness in the recognition of emotional pictures.

Sleep has a beneficial effect on memory consolidation. However, its role in emotional memory is currently debated. Here, we investigate the role of sleep and a similar period of wakefulness on the recognition of emotional pictures and subjective emotional reactivity. Forty participants without any major physical, neurological or psychological condition were randomly assigned to the Sleep First Group or Wake First Group. The two groups underwent the encoding phase of an emotional images task with negative and neutral pictures at either 09:00 hours (Wake First Group) or 21:00 hours (Sleep First Group). Then participants performed an immediate recognition test (T1), and two delayed tests 12 hr (T2) and 24 hr (T3) later. Perceived arousal and valence levels were collected for each picture. Sleep parameters were recorded at participants' homes with a portable device. No differences were observed at T1, whereas at T2 the Sleep First Group showed a higher memory performance than the Wake First Group. At T3, performance decreased in the Sleep First Group (who spent the previous 12 hr awake), but not in the Wake First Group (who slept during the previous 12 hr). Overall, negative images were remembered better than neutral ones. We also observed a positive association between memory performance for negative items at the immediate test and the percentage of rapid eye movement sleep the night before the encoding. Our data confirm that negative information is remembered better over time than neutral information, and that sleep benefits the retention of declarative information. However, sleep seems not to preferentially improve emotional memory, although it may affect the encoding of negative information.

Changes in dream features across the first and second waves of the Covid-19 pandemic.

Research during the Covid-19 pandemic has highlighted its significant impact on dreaming. Here we address changes in dream features both during the first wave, when the Italian government imposed a total lockdown, and the second wave (autumn 2020), when a partial lockdown was effected. In April 2020 (total lockdown), 1,622 participants (Mage  = 34.1 ± 13.6 years; 1171F) completed an online survey including the Pittsburgh Sleep Quality Index and a set of questions on dream features and their possible changes relative to the month preceding the lockdown (pre-total lockdown). In November 2020 (partial lockdown), 214 participants (Mage  = 36.78 ± 14.2 years; 159F) from the previous sample completed the same survey. Approximately half of the subjects reported increased or decreased dream frequency (30.5% and 21.8%), length (27.1% and 15.8%) and vividness (31.5% and 17.1%) during total lockdown as well as during partial lockdown (frequency: 30.3% and 13.5%; length: 23.3% and 12.6%; vividness: 31.6% and 24.1%). Dream affect became significantly more negative in total lockdown relative to pre-total lockdown and in partial lockdown relative to pre-partial lockdown (both p < .001). Both in total lockdown and partial lockdown, increased negative dream emotionality significantly predicted changes in dream frequency, length and vividness, and was significantly predicted, in turn, by worsened sleep quality. Our data confirm that dream features are significantly affected by major life changes such as those imposed by a pandemic. The fact that between lockdowns negative dream affect returned almost to baseline level suggests that dream emotionality is closely related to lifestyle and wake-time emotional changes. Also, our findings point to a modulating role of sleep quality on dream emotionality.

How Elderly People's Quality of Life Relates to Their Sleep Quality and Sleep-Related Beliefs.

OBJECTIVE/BACKGROUND: Quality of life (QoL) is a broad multidimensional construct, which can be influenced by several factors across the lifespan, including sleep quality. The aim of this study was to examine the association between QoL (and its specific domains), objective and self-reported sleep quality, and subjective sleep-related factors (i.e., dysfunctional beliefs and attitudes about sleep, and metacognitive beliefs about sleeping difficulties) in healthy elderly people. PARTICIPANTS: Fifty healthy older adults (mean age = 70.40 years, SD = 7.43) participated in the study. METHODS: QoL was assessed using the World Health Organization's Quality of Life Assessment, BREF version (WHOQOL-BREF). Self-reported sleep quality and efficiency were measured with the Pittsburgh Sleep Quality Index (PSQI) and sleep diary. Dysfunctional beliefs and attitudes about sleep (DBAS), and metacognitive beliefs about sleeping difficulties (MCQ-I) (subjective sleep-related factors) were assessed with self-report questionnaires. Objective sleep quality and efficiency were measured using actigraphy over 7 days. RESULTS: Regression analyses showed that self-reported sleep efficiency and dysfunctional beliefs and attitudes about sleep explained 24% of the variance in global QoL. Dysfunctional beliefs and attitudes about sleep were the only significant predictor of QoL in the environmental domain. CONCLUSIONS: Taken together, these findings underscore the influence of sleep-related factors, and particularly dysfunctional beliefs and attitudes about sleep, along with sleep efficiency, on the perception of QoL in healthy older adults. These factors need to be considered in efforts to sustain QoL, in late adulthood at least.

Maintaining social support while social distancing: The longitudinal benefit of basic psychological needs for symptoms of anxiety during the COVID-19 outbreak.

Although social distancing measures could be potentially perceived as thwarting conditions for basic psychological needs and thus causing psychological distress, off(on)line social support could compensate for this frustration by providing psychological proximity. Using self-determination theory, in this study, we aimed (a) to evaluate the change of perception in need satisfaction over time (before and during home-confinement and after a month of lockdown) and (b) to test the short-term longitudinal association between off(on)line social support, basic needs, and anxiety during social distancing measures in response to the COVID-19 outbreak. During the lockdown period decreed by Italy in March 2019 to confront the COVID-19 emergency, 1344 participants completed an online questionnaire and 131 participants completed a follow-up after 1 month. Results showed a decrease in need satisfaction during home confinement and a further reduction after a month of lockdown. Cross-sectional path analysis showed that both online and offline social support were associated with higher need satisfaction, which, in turn, was related to a lower level of anxiety. Longitudinal paths also confirmed the association between need satisfaction and anxiety. Collectively, these results suggest that maintaining psychological proximity despite social distancing measures may provide important avenues for reducing negative outcomes during forced home confinement.

Moral judgment, decision times and emotional salience of a new developed set of sacrificial manual driving dilemmas.

The growing interest in the subject of moral judgment in driver and autonomous vehicle behavior highlights the importance of investigating the suitability of sacrificial dilemmas as experimental tools in the context of traffic psychology. To this aim a set of validated sacrificial trolley problems and a new set of trolley-like driving dilemmas were compared through an online survey experiment, providing normative values for rates of participants' choices; decision times; evaluation of emotional valence and arousal experienced during the decision process; and ratings of the moral acceptability. Results showed that while both sets of dilemmas led to a more frequent selection of utilitarian outcomes, the driving-type dilemmas seemed to enhance faster decisions mainly based on the utilitarian moral code. No further differences were observed between the two sets, confirming the reliability of the moral dilemma tool in the investigation of moral driving behaviors. We suggest that as moral judgments and behaviors become more lifelike, the individual's moral inclination emerge more automatically and effectively. This new driving-type dilemma set may help researchers who work in traffic psychology and moral decision-making to approach the complex task of developing realistic moral scenarios more easily in the context of autonomous and nonautonomous transportation.

Sleep and Psychological Difficulties in Italian School-Age Children During COVID-19 Lockdown.

OBJECTIVE: On March 10, 2020, the Italian Government ordered a national lockdown to limit the viral transmission of coronavirus disease 2019 infections. This study investigated how these restrictive measures have impacted sleep quality, timing, and psychological difficulties in school-age children and their mothers during the lockdown. METHODS: In an online survey, 299 mothers reported their sleep habits, experience of time, and psychological difficulties as well as those of their children (6-10 years old) during and, retrospectively, before the lockdown. RESULTS: During the lockdown, children showed a marked delay in sleep timing-that is, later bedtime and rise time-and a mild worsening in sleep quality. They were less prone to respect daily routines or to keep track of the passage of time. They showed increased emotional, conduct, and hyperactive symptoms, and the increase in these psychological difficulties was predicted by the change in sleep quality, boredom, and mothers' psychological difficulties. In addition, mothers showed a delayed sleep timing and worsening of sleep quality during the lockdown, in varying degrees depending on their working conditions. Mothers who kept working regularly outside their homes during lockdown reported more regular sleep patterns, whereas mothers who stopped working showed more emotional symptoms and relevant changes in their perception of time. CONCLUSIONS: Overall, given the evidence of the adverse behavioral and psychological impact of home confinement and social restrictions, effective measures needed to be in place to mitigate long-term effects on children and their mothers, especially those who have had to stop working during lockdown.

The interplay between mothers' and children behavioral and psychological factors during COVID-19: an Italian study.

Italy has been the first nation outside of Asia to face the COVID-19 outbreak. To limit viral transmission of infection, by March 10th, 2020, the Italian Government has ordered a national lockdown, which established home confinement, home (smart) working, and temporary closure of non-essential businesses and schools. The present study investigated how these restrictive measures impacted mothers and their pre-school children's behavioral habits (i.e., sleep timing and quality, subjective time experience) and psychological well-being (i.e., emotion regulation, self-regulation capacity). An online survey was administered to 245 mothers with pre-school children (from 2 to 5 years). Mothers were asked to fill the survey thinking both on their habits, behaviors, and emotions and on those of their children during the quarantine, and retrospectively, before the national lockdown (i.e., in late February). A general worsening of sleep quality and distortion of time experience in both mothers and children, as well as increasing emotional symptoms and self-regulation difficulties in children, was observed. Moreover, even when the interplay between the behavioral and psychological factors was investigated, the factor that seems to mostly impact both mothers' and children's psychological well-being was their sleep quality. Overall, central institutions urgently need to implementing special programs for families, including not only psychological support to sustain families with working parents and ameliorating children's management.

Changes in sleep pattern, sense of time and digital media use during COVID-19 lockdown in Italy.

Italy is one of the major COVID-19 hotspots. To reduce the spread of the infections and the pressure on Italian healthcare systems, since March 10, 2020, Italy has been under a total lockdown, forcing people into home confinement. Here we present data from 1,310 people living in the Italian territory (Mage  = 23.91 ± 3.60 years, 880 females, 501 workers, 809 university students), who completed an online survey from March 24 to March 28, 2020. In the survey, we asked participants to think about their use of digital media before going to bed, their sleep pattern and their subjective experience of time in the previous week (March 17-23, which was the second week of the lockdown) and up to the first week of February (February 3-10, before any restriction in any Italian area). During the lockdown, people increased the usage of digital media near bedtime, but this change did not affect sleep habits. Nevertheless, during home confinement, sleep timing markedly changed, with people going to bed and waking up later, and spending more time in bed, but, paradoxically, also reporting a lower sleep quality. The increase in sleep difficulties was stronger for people with a higher level of depression, anxiety and stress symptomatology, and associated with the feeling of elongation of time. Considering that the lockdown is likely to continue for weeks, research data are urgently needed to support decision making, to build public awareness and to provide timely and supportive psychosocial interventions.

The effect of complex cognitive training on subsequent night sleep.

Using a nap design, we have recently shown that training at a complex cognitive task at bedtime improves objective sleep quality by reducing sleep fragmentation. In order to extend our findings to nighttime sleep, here we assess the impact of a multi-componential cognitive task at bedtime on the subsequent sleep episode of subjects reporting habitual bad sleep, allegedly characterized by high sleep fragmentation. In a within-subjects design, 20 subjective bad sleepers underwent polysomnographic recording in three conditions: (a) baseline sleep (BL); (b) post-training sleep (TR), preceded by a complex ecological task, i.e. a modified version of the word game Ruzzle; (c) post-active control sleep (AC), preceded by a control task. Sleep in TR was more organized (higher number of cycles and longer time spent in cycles) and showed lower microarousal frequency than in AC and BL. As for sleep continuity (total and brief awakening frequency) and other stability measures (state transition and functional uncertainty period frequency, time in functional uncertainty), both TR and AC showed significant improvements compared with BL. Arousal frequency was also reduced in TR relative to BL. Our results show a clear impact of cognitive training on subsequent night sleep, basically consisting of an increase in sleep continuity, stability and organization. In our sample of bad sleepers, these post-training changes end up representing a notable sleep improvement, also consistently reflected in subjective sleep quality perception. Therefore, ecological pre-sleep cognitive training should be further studied as an easily accessible complementary approach in standard therapies for sleep-disordered populations.

Sleep quality improves during treatment with repetitive transcranial magnetic stimulation (rTMS) in patients with cocaine use disorder: a retrospective observational study.

BACKGROUND: Sleep disturbance is a prominent and common complaint in people with cocaine use disorder (CUD), either during intake or withdrawal. Repetitive transcranial magnetic stimulation (rTMS) has shown promise as a treatment for CUD. Thus, we evaluated the relationship between self-perceived sleep quality and cocaine use pattern variables in outpatients with CUD undergoing an rTMS protocol targeted at the left dorsolateral prefrontal cortex. METHODS: This is a retrospective observational study including 87 patients diagnosed with CUD according to the DSM-5 criteria. Scores in Pittsburgh Sleep Quality Index (PSQI), Cocaine Craving Questionnaire (CCQ), Beck Depression Inventory-II (BDI-II), Self-rating Anxiety Scale (SAS), and Symptoms checklist 90-Revised (outcome used: Global Severity Index, GSI) were recorded at baseline, and after 5, 30, 60, and 90 days of rTMS treatment. Cocaine use was assessed by self-report and regular urine screens. RESULTS: Sleep disturbances (PSQI scores > 5) were common in patients at baseline (mean ± SD; PSQI score baseline: 9.24 ± 3.89; PSQI > 5 in 88.5% of patients). PSQI scores significantly improved after rTMS treatment (PSQI score Day 90: 6.12 ± 3.32). Significant and consistent improvements were also seen in craving and in negative-affect symptoms compared to baseline. Considering the lack of a control group, in order to help the conceptualization of the outcomes, we compared the results to a wait-list group (n = 10). No significant improvements were observed in the wait-list group in any of the outcome measures. CONCLUSIONS: The present findings support the therapeutic role of rTMS interventions for reducing cocaine use and accompanying symptoms such as sleep disturbance and negative-affect symptoms. TRIAL REGISTRATION: ClinicalTrials.gov.NCT03733821.

The role of sleep in the formation and updating of abstract mental representations.

According to Gilead and colleagues, to be efficient abstraction requires a hierarchical organization of information into long-term memory. But, how and when are abstract representations consolidated into long-term memory and how are they integrated with pre-existing abstracta are questions not discussed by Gilead and colleagues. Here, we propose that these processes occur preferentially during offline periods such as sleep.

Autonomic activity during sleep predicts memory consolidation in humans.

Throughout history, psychologists and philosophers have proposed that good sleep benefits memory, yet current studies focusing on the relationship between traditionally reported sleep features (e.g., minutes in sleep stages) and changes in memory performance show contradictory findings. This discrepancy suggests that there are events occurring during sleep that have not yet been considered. The autonomic nervous system (ANS) shows strong variation across sleep stages. Also, increases in ANS activity during waking, as measured by heart rate variability (HRV), have been correlated with memory improvement. However, the role of ANS in sleep-dependent memory consolidation has never been examined. Here, we examined whether changes in cardiac ANS activity (HRV) during a daytime nap were related to performance on two memory conditions (Primed and Repeated) and a nonmemory control condition on the Remote Associates Test. In line with prior studies, we found sleep-dependent improvement in the Primed condition compared with the Quiet Wake control condition. Using regression analyses, we compared the proportion of variance in performance associated with traditionally reported sleep features (model 1) vs. sleep features and HRV during sleep (model 2). For both the Primed and Repeated conditions, model 2 (sleep + HRV) predicted performance significantly better (73% and 58% of variance explained, respectively) compared with model 1 (sleep only, 46% and 26% of variance explained, respectively). These findings present the first evidence, to our knowledge, that ANS activity may be one potential mechanism driving sleep-dependent plasticity.

Cardiac autonomic activity during daytime nap in young adults.

The current study investigated both sympathetic and vagal autonomic patterns during a daytime sleep in 25 healthy adults (23.2 ± 2.4 years). Pre-ejection period (PEP; related inversely to beta-adrenergic sympathetic activity), the interval between consecutive R-waves (RR) and frequency-domain heart rate variability (HRV) were computed during pre-nap wakefulness and undisturbed sleep stages. Results showed sleep-related changes in RR and HRV measures, whereas PEP decreased significantly from pre-nap to sleep, showing no differences across sleep stages. Moreover, pre-nap PEP and HFnu (the normalized unit of the high-frequency component of HRV) were associated negatively with sleep latency and wake after sleep onset. These results indicate a marked autonomic output reduction during daytime sleep, with different stage-dependent fluctuations for sympathetic and vagal activity. Importantly, pre-nap autonomic activity seems to modulate subsequent sleep quality.

Sleep and memory consolidation: a common mechanism across species?

In humans, memory consolidation can be aided by the representation of an odor previously associated with target information during sleep. In an elegant study, Zwaka et al. (Curr Biol 25: 2869-2874, 2015) have demonstrated that the same process occurs in honeybees, suggesting that the relationship between sleep and memory may be similar across different animal species.

Sleep before and after learning promotes the consolidation of both neutral and emotional information regardless of REM presence.

Sleep may play a role in consolidating emotional memories. However, studies on the effects of REM sleep on negative vs. neutral memories have produced inconsistent evidence. Here, we assess the role of NREM and REM sleep before and after learning in promoting the consolidation of neutral and arousing pleasant and unpleasant memories. Forty-six (32 F) healthy university students were exposed to a set of pictures at 1:00PM (Session 1) and to an equivalent set at 4:45PM (Session 2). All the pictures in Session 1 and Session 2 were presented again, intermixed with new similar pictures at 5:15PM in a memory recognition task. Following Session 1, participants took a 90/120-min nap (NAP group), while 16 participants remained awake (WAKE group). Via polysomnographic recording, the NAP group was segregated into REM (N=14) and NoREM groups (N=16). Indices of memory consolidation for both stimuli presented before (discriminability of Session 1 pictures in Session 3) and after sleep (discriminability of Session 2 pictures in Session 3) were calculated. Memory consolidation for pictures presented both before and after the sleep period was higher in the NAP group as compared to the WAKE group, but no differential role of REM sleep emerged. A memory consolidation advantage was evident for neutral over pleasant (but not unpleasant) pictures. Taken together, these results indicate that a daytime nap (with or without REM sleep) facilitates consolidation of declarative memories presented before and after sleep irrespective of their valence.

Heart rate variability helps tracking time more accurately.

Adequate temporal abilities are crucial for adaptive behavior. In time processing, variations in the rate of pulses' emission by the pacemaker are often reported to be an important cause of temporal errors. These variations are often associated with physiological changes, and recently it has also been proposed that physiological changes may not just vary the pulses' emission, but they can work as a timekeeper themselves. In the present study we further explore the relationship between temporal abilities with autonomic activity and interoceptive awareness in a group of thirty healthy young adults (mean age 24.18 years; SD=2.1). Using electrocardiogram, impedance cardiography and skin conductance measures, we assessed the relationship between the autonomic profile at rest and temporal abilities in two temporal tasks (time bisection and finger tapping tasks). Results showed that heart rate variability affects time perception. We observed that increased heart rate variability (HRV) was associated with higher temporal accuracy. More specifically, we found that higher vagal control was associated with lower error in producing 1-s tempo, whereas higher overall HRV was related with lower error (measured by the constant error) in the time bisection task. Our results support the idea that bodily signals may shape our perception of time.