ERPs and contextual semantic discrimination: degrees of congruence in wakefulness and sleep

This study explores whether the brain can discriminate degrees of semantic congruency during wakefulness and sleep. Experiment 1 was conducted during wakefulness to test degrees of congruency by means of N400 amplitude. In Experiment 2, the same paradigm was applied to a different group of participants during natural night sleep. Stimuli were 108 sentences (definitions with two attributes) with four possible degrees of congruence as ending targets. In both studies, the amplitude of N400-like effect showed modulation according to the degree of congruency. The results indicate that the brain can accomplish sentential semantic discriminations not only in wakefulness but also in sleep.     

睡眠研究若干现代理论问题

最近十年间睡眠研究日益引起全世界的重视,除我国等纷纷建立“睡眠研究会”外,并新 建“亚洲睡眠研究会”和“世界睡眠研究联合会”。本文探讨睡眠研究的若干现代理论问题,其 中包括睡眠的核心是深度慢波睡眠问题,睡眠如何受制于“２４－ｈ昼夜节律”,异相睡眠和觉醒 的比较分析,世界范围内重新评价午睡的重要性,临床睡眠疾患及其对策和介诏内源性促眠物质等。     

Mental time travel to the future might be reduced in sleep

We present a quantitative study of mental time travel to the future in sleep. Three independent, blind judges analysed a total of 563 physiology-monitored mentation reports from sleep onset, REM sleep, non-REM sleep, and waking. The linguistic tool for the mentation report analysis is based on established grammatical and cognitive-semantic theories and has been validated in previous studies. Our data indicate that REM and non-REM sleep must be characterized by a reduction in mental time travel to the future, which would support earlier physiological evidence at the level of brain function.     

Effects of sleep on positive,negative and neutral valenced story and image memory

During sleep, emotional memories are preferentially strengthened. However, most studies on sleep and emotional memory focus on comparing negative valence with neutral valence stimuli. This study compared the sleep-dependent memory effects for stories and images, each comprising negative, neutral, and positive stimuli. It was hypothesized that a sleep effect would be seen for negatively and positively valenced stimuli. A novel story memory task (comprising three stories), and photographs from the Nencki Affective Picture database were presented for learning to 61 healthy adults (ages 18–25). They were tested for memory on the two tasks immediately, and then again after either a 2-hr nap (n = 31; 17 women, 14 men) or 2-hr wake period (n = 30; 13 women, 17 men). At second testing, the sleep condition had significantly better recall compared to the wake condition on both tasks. There was a relationship with valence only for the story task, with better performance for the sleep condition on the negatively and positively valenced texts, but not on the neutral text. There were no significant relationships between memory measures and sleep-stage duration and EEG power variables. The story memory findings support the hypothesis that memory consolidation prioritizes emotional memory, whether positively or negatively valenced.     

Le sommeil des étudiants français en période de COVID-19 : Influence des deux premiers confinements sur la quantité et la qualité de sommeil

The COVID-19 pandemic resulted in two periods of confinement during the year 2020 that led to changes in lifestyle patterns. The purpose of our study was to assess the impact of the lockdowns on the quantity (i.e., schedule and time in bed) and quality (i.e., difficulties and parasomnias) of sleep in French college students. During the first and second lockdowns, students were asked to answer an online questionnaire consisting of 23 questions. This questionnaire gathered information on the real and ideal schedules of getting up and going to bed, the time in bed, as well as the parasomnias and difficulties related to sleep (difficulties in falling asleep, waking up, lack of sleep feeling). The results showed that students slept later and spent more time in bed on week-ends than during the week, with these effects being more pronounced during the first confinement than during the second. The majority of students reported poor sleep quality, difficulty falling asleep, early awakening, and a feeling of sleep deprivation. The most common parasomnias were episodes of nightmares and sleepiness. Sleep difficulties and reported parasomnias were greater during the second confinement than during the first. Sleep debt, was still present during the lockdowns. The reported sleep difficulties and parasomnias reflect poor sleep quality, despite the reduction in social constraints. Explanatory hypotheses as well as prevention perspectives regarding sleep hygiene were considered.     

Aging and sleep deprivation affect different neurocognitive stages of spatial information processing during a virtual driving task – An ERP study

We have previously shown that aging deteriorates detection of spatial visual and auditory stimuli and prolongs reaction times measured during a virtual driving task. Sleep deprivation affected the young more than the old. Here we determined the effects of age and sleep deprivation on ERPs elicited by spatial visual and auditory stimuli during virtual driving. Participants were 22 young (18–35 years) and 19 old (65–79) healthy males. Experiments were run in normal daytime condition and after a night of sleep deprivation. Aging shortened the peak latencies of the early P1 and N1 but increased the P3 latency. Sleep deprivation slowed down and diminished the N1 peaks of the young. General right-side preference was seen in latencies. Thus, the effects of aging could be seen in decision making and working memory related processes (P3), whereas those of sleep deprivation could be found in alerting and orienting functions (N1) in the young.     

Beginning the workday yet already depleted? Consequences of late-night smartphone use and sleep

Smartphones have become a prevalent technology as they provide employees with instant access to work-related information and communications outside of the office. Despite these advantages, there may be some costs of smartphone use for work at night. Drawing from ego depletion theory, we examined whether smartphone use depletes employees’ regulatory resources and impairs their engagement at work the following day. Across two studies using experience sampling methodology, we found that smartphone use for work at night increased depletion the next morning via its effects on sleep. Morning depletion in turn diminished daily work engagement. The indirect effects of smartphone use on depletion and engagement the next day were incremental to the effects of other electronic devices (e.g., computer, tablet, and television use). We also found some support that the negative effects of morning depletion on daily work engagement may be buffered by job control, such that depletion impairs work engagement only for employees who experience low job control.     

Will students pass a competitive exam that they failed in their dreams?

We tested whether dreams can anticipate a stressful exam and how failure/success in dreams affect next-day performance. We collected information on students’ dreams during the night preceding the medical school entrance exam. Demographic, academic, sleep and dream characteristics were compared to the students’ grades on the exam. Of the 719 respondents to the questionnaire (of 2324 total students), 60.4% dreamt of the exam during the night preceding it. Problems with the exam appeared in 78% of dreams and primarily involved being late and forgetting answers. Reporting a dream about the exam on the pre-exam night was associated with better performance on the exam (p = .01). The frequency of dreams concerning the exam during the first term predicted proportionally higher performance on the exam (R = 0.1, p = .01). These results suggest that the negative anticipation of a stressful event in dreams is common and that this episodic simulation provides a cognitive gain.