Sleep and psychological characteristics in habitual self-awakeners and forced awakeners.

Previous studies described the modifications of physiological and behavioural variables associated with self-awakening, while only few studies assessed subjective sleep quality and psychological characteristics in habitual self-awakeners. Here we investigated self-reported sleep habits and features, as well as psychological variables of habitual self-awakeners and forced-awakeners, with special regard to subjective sleep quality, personality characteristics, anxiety and depression symptoms. In our sample, the prevalence of habitual self-awakeners was 15.1%. Compared to forced-awakeners, habitual self-awakeners showed more regular sleep/wake schedules and were more frequently morning types. Moreover, habitual self-awakeners referred to be more satisfied about their sleep, to wake up more easily in the morning, to need less time to get out of bed and to feel more refreshed upon awakening than forced-awakeners. We also observed an association between the habit of self-awakening and the "ability" to set the awakening to an unusual time. Concerning psychological features, habitual self-awakeners showed higher scores in Conscientiousness and Openness and lower scores in Extraversion compared to forced-awakeners, whereas no differences between groups emerged for anxiety and depression levels. In conclusion, our findings point to an association between the habit of self-awakening and good subjective sleep quality. In this perspective, future research should objectively test in detail the effects of the self-awakening habit on sleep structure and organization, taking into account also microstructural sleep features

False memories formation is increased in individuals with insomnia

Previous studies suggest that sleep can influence false memories formation. Specifically, acute sleep loss has been shown to promote false memories production by impairing memory retrieval at subsequent testing. Surprisingly, the relationship between sleep and false memories has only been investigated in healthy subjects but not in individuals with insomnia, whose sleep is objectively impaired compared to healthy subjects. Indeed, this population shows several cognitive impairments involving prefrontal functioning that could affect source monitoring processes and contribute to false memories generation. Moreover, it has been previously reported that subjects with insomnia differentially process sleep-related versus neutral stimuli. Therefore, the aim of the present study was to compare false memories production between individuals with insomnia symptoms and good sleepers, and to evaluate the possible influence of stimulus category (neutral versus sleep-related) in the two groups. The results show that false memories are globally increased in participants reporting insomnia symptoms compared to good sleepers. A reduction in source monitoring ability was also observed in the former group, suggesting that an impairment of this executive function could be especially involved in false memories formation. Moreover, our data seem to confirm that false memories production in individuals with insomnia symptoms appears significantly modulated by stimulus category

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\ua0=\ua034.1\ua0\ub1\ua013.6 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\ua0=\ua036.78\ua0\ub1\ua014.2\ua0years; 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\ua0<.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

Sleep enhances strategic thinking at the expense of basic procedural skills consolidation

Recent studies show that sleep facilitates the learning of complex cognitive skills. Here, we assess the effect of sleep on performance in an ecological, multi-componential task, which requires subjects to trace on a screen as many words as possible with 16 letters, some of which (“bonuses”) multiply the value of letters or words containing them. In a within-subjects design, 23 healthy adults underwent training and retest, with a retention period (approximately 8&nbsp;hr) spent awake (WK, with training in the morning and retest in the afternoon) or asleep (SL, with training in the evening and retest in the morning). The main performance measure (GLOB) results from the total value of the letters used, the number of words, their length and the strategic use of bonus letters. An additional measure (WORDS, i.e., the proportion of words correctly detected over all detectable words) was also used, mainly reflecting procedural rather than strategic skills. In WK, although GLOB increased at retest, a significant improvement emerged only for WORDS, whereas in SL only GLOB was enhanced. In WK, the GLOB improvement appears to depend on the increase in the number of words detected (GLOB and WORDS improvement measures were positively associated), whereas in SL this association was not observed, indicating a shift to more complex but more rewarding strategies. Our data contribute to the understanding of everyday life learning processes by suggesting that sleep benefits memories of future relevance and promotes preferential consolidation of strategic skills when this is useful to achieve one's goal

The effects of pre-sleep training on sleep continuity, stability and organization in elderly individuals.

Several studies have consistently shown that pre-sleep learning is associated to changes of sleep structure. Whereas previous research has mainly focused on sleep states, namely REM and NREM amount, very little attention has been paid to the hypothesis that pre-sleep learning might improve sleep continuity, stability, and cyclic organization, which are often impaired in aging.Thus, aim of this researchwas to assess, in a sample of 18 healthy elderly subjects, whether a memory task administered at bedtime would determine changes in any sleep parameter, with special regard to sleep continuity, stability, and organization. To this purpose, a baseline sleep (BL), i.e., a normal sleep with 9-h time in bed (TIB), was compared to a post-training sleep (TR), with the same TIB but preceded by an intensive training session. For the latter, a verbal declarative task was used, consisting in learning paired-word lists, rehearsed, and recalled for three times in a row. To control for individual learning abilities, subjects were administered several sets of lists with increasing difficulty, until they reached an error rate 20% at third recall. Relative to BL, TR shows a significant reduction in the frequency of brief awakenings, arousals, state transitions, “functional uncertainty” (FU) periods, and in the percentage of time in FU over total sleep time (TST). A significant increase in the number of complete cycles, total cycle time (TCT), and TCT/TST proportion was also found. All these changes are evenly distributed over the sleep episode. No sleep stage measure display significant changes, apart from a slight reduction in the percentage of Stage 1. Scores at retest are negatively correlated with both the frequency of arousals and of state transitions. Our data suggest that pre-sleep learning can yield a beneficial re-organizing effect on elderlies’ sleep quality. The inverse correlation between recall scores and the measures of sleep continuity and stability provides further support to the role of these features in memory processes

Diurnal variation of spontaneous eye blink rate in the elderly and its relationships with sleepiness and arousal

Sleep-wake rhythms in the elderly are deeply modified compared to young subjects, irrespective of physical or mental illnesses. However, still controversial are the results about age-related circadian variations of sleepiness levels. The objective of this study is to investigate the profile of diurnal sleepiness in healthy elderly subjects through subjective scales and by measuring spontaneous eye-blink rate (BR). In fact, we have previously found that BR, a reliable and non-invasive peripheral measure of central dopamine activity, increases in the young at times when subjective sleepiness is increased. Twelve healthy elderly volunteers (F = 9, M = 3, age range 64-79) participated in the experiment. At four times during the day (10 a.m., 1.30 p.m., 5 p.m., 8.30 p.m.), Karolinska sleepiness scale and a visual analogue scale for mood were administered to the subjects and BR was measured through vertical EOG. Alpha EEG power was used as objective measure of sleepiness. Sleepiness significantly changes across the day; according to post hoc contrasts, this is due to more sleepiness at 5 p.m. Future research should be aimed at clarifying whether this peak is related to phase-advanced core body temperature in elderly people. Differently from the young, no significant differences were found in BR across the day, suggesting that an age-related modification of dopaminergic arousal mechanisms counteracting the rising sleep drive should be further explored. © 2009 Elsevier Ireland Ltd. All rights reserved

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