The function of REM and NREM sleep on memory distortion and consolidation.

During rapid eye movement (REM) sleep, newly consolidated memories can be distorted to adjust the existing memory base in memory integration. However, only a few studies have demonstrated the role of REM sleep in memory distortion. The present study aims to clarify the role of REM sleep in the facilitation of memory distortion, that is, hindsight bias, compared to non-rapid eye movement (NREM) sleep and wake states. The split-night paradigm was used to segregate REM and NREM sleep. The hypotheses are (1) hindsight bias-memory distortion-is more substantial during REM-rich sleep (late-night sleep) than during NREM-rich sleep (early-night sleep); (2) memory stabilization is more substantial during NREM-rich sleep (early-night sleep) than during REM-rich sleep (late-night sleep); and (3) memory distortion takes longer time than memory stabilization. The results of the hindsight bias test show that more memory distortions were observed after the REM condition in comparison to the NREM condition. Contrary to the hindsight bias, the correct response in the word-pair association test was observed more in the NREM than in the REM condition. The difference in the hindsight bias index between the REM and NREM conditions was identified only one week later. Comparatively, the difference in correct responses in the word-pair association task between the conditions appeared three hours later and one week later. The present study found that (1) memory distortion occurs more during REM-rich sleep than during NREM-rich sleep, while memory stabilization occurs more during NREM-rich sleep than during REM-rich sleep. Moreover, (2) the newly encoded memory could be stabilized immediately after encoding, but memory distortion occurs over several days. These results suggest that the roles of NREM and REM sleep in memory processes could be different.

Memory load of information encoded amplifies the magnitude of hindsight bias.

Our recollections tend to become more similar to the correct information when we recollect an initial response using the correct information, known as the hindsight bias. This study investigated the effect of memory load of information encoded on the hindsight bias's magnitude. We assigned participants (N = 63) to either LOW or HIGH conditions, in which they answered 20 or 50 questions, which were their initial responses. Then, they memorized and remembered the correct information. They finally recollected the initial responses. Twenty of the fifty questions in the HIGH condition were identical to those in the LOW condition. We used the answers to these 20 common questions in LOW and HIGH conditions to examine the effect of the memory load of information encoded, defined as the number of correct answers to remember (i.e., 20 or 50) on the hindsight bias. Results indicated that the magnitude of the hindsight bias was more prominent in the HIGH than the LOW condition, suggesting that the memory load amplifies the hindsight bias's magnitude. This finding also implies that controlling the memory load of information encoded when learning correct information could mitigate the hindsight bias. We expect these findings to have practical implications in occupational settings where hindsight bias could lead to critical errors such as financial losses or medical problems.

Effects of outdoor artificial light at night on human health and behavior: A literature review.

The quality of life of human beings has improved tremendously through improved productivity, convenience, safety, and livability due to nighttime lights that illuminate outdoor work, leisure, and mobility. Recently, however, concerns have been growing over outdoor artificial light at night (ALAN) and its effects on human beings as well as ecosystems including animals and plants. This literature review aims to deliver a critical overview of the findings and the areas for future research on the effects of outdoor ALAN on human health and behaviors. Through a narrative literature review, we found that scientific research crucially lacks studies on the effects of outdoor ALAN on human behaviors and health, including social interaction, which may be more widespread compared to what is recognized so far. This review also highlights the importance of investigating the causal and complex relationships between outdoor ALAN, health, and behaviors with sleep as a key mediating factor. We elucidate that outdoor ALAN has both positive and negative effects on human life. Therefore, it is important for societies to be able to access facts and evidence about these effects to plan, agree to, and realize the optimal usage of nighttime lighting that balances its merits and demerits. Researchers in related areas of study must investigate and deliver the science of outdoor ALAN to various stakeholders, such as citizens, policymakers, urban and landscape planners, relevant practitioners, and industries. We believe that our review improves the understanding of outdoor ALAN in relation to human life and contributes to sustainable and thriving societies.

Discrepancies Between Beliefs and Practices on Sleep as a Factor of Insomnia and Negative Feelings.

Two online surveys were conducted in Japan to develop and validate the Sleep Belief-Practice Index (SBPI) scales, a pair of new scales designed to measure beliefs (SBPI-B) and practices (SBPI-P) on sleep and its environment. Their discrepancies (SBPI-D) were calculated as differences between SBPI-B and -P. In Survey 1 (N = 400), survey data of the pilot version of the scales were entered into an exploratory factor analysis to obtain a meaningful set of scale items. In Survey 2 (N = 2952), survey data were entered into a confirmatory factor analysis and then correlation analyses to confirm associations of SBPI-D with insomnia and positive and negative feelings. Furthermore, participants were categorized into four groups according to the degree and combination of sleep beliefs and practices to compare the status of insomnia and positive and negative feelings by the groups. As a result of factor analyses, we obtained 13 common item scales of SBPI-B and -P. SBPI-D was positively correlated with insomnia and negative feelings. In addition, the group with high-scoring beliefs in SBPI-B and low-scoring practices in SBPI-P showed the most severe insomnia and negative feelings among the four groups. These results suggest that the belief-practice discrepancy about sleep can explain one aspect of insomnia.

Counteracting effect of verbal ratings of sleepiness on dual task interference.

The aim of the present study was to demonstrate the effect of verbal ratings on arousal in the electroencephalogram (EEG) and psychomotor vigilance test (PVT) performance. Thirty participants underwent the PVT for 40 min in three experimental conditions: (1) Rating condition, in which they verbally rated subjective sleepiness with Karolinska sleepiness scale, following pure tone sound played every 20 s during PVT, (2) No-rating condition, in which they underwent PVT with the similar sound as the Rating experiment but without the verbal rating task, and (3) Control condition, in which they underwent PVT with a no-sound stimulus and without the verbal rating task. The results show that during the first half of the task epoch, alpha power density was lower in the Rating than in the No-rating condition, while performance was not different between the conditions. During the second half of the task epoch, performance was better in the Non-rating than in the Rating condition, but no difference in the alpha power density. These results suggest that performance deterioration could be masked by the arousal effect of the dual task itself. It could also explain why the PVT performance and arousal in EEG sometimes dissociate, particularly in dual task situations.

Tracking intermediate performance of vigilant attention using multiple eye metrics.

Vigilance deficits account for a substantial number of accidents and errors. Current techniques to detect vigilance impairment measure only the most severe level evident in eyelid closure and falling asleep, which is often too late to avoid an accident or error. The present study sought to identify ocular biometrics of intermediate impairment of vigilance and develop a new technique that could detect a range of deficits in vigilant attention (VA). Sixteen healthy adults performed well-validated Psychomotor Vigilance Test (PVT) for tracking vigilance attention while undergoing simultaneous recording of eye metrics every 2 hours during 38 hours of continuous wakefulness. A novel marker was found that measured VA when the eyes were open-the prevalence of microsaccades. Notably, the prevalence of microsaccades decreased in response to sleep deprivation and time-on-task. In addition, a novel algorithm for detecting multilevel VA was developed, which estimated performance on the PVT by integrating the novel marker with other eye-related indices. The novel algorithm also tracked changes in intermediate level of VA (specific reaction times in the PVT, i.e. 300-500 ms) during prolonged time-on-task and sleep deprivation, which had not been tracked previously by conventional techniques. The implication of the findings is that this novel algorithm, named "eye-metrical estimation version of the PVT: PVT-E," can be used to reduce human-error-related accidents caused by vigilance impairment even when its level is intermediate.

Positive associations of optimism-pessimism orientation with pro-environmental behavior and subjective well-being: a longitudinal study on quality of life and everyday behavior.

PURPOSE: The aim of the present study was to investigate associations of the balance of optimism and pessimism orientations as personal traits with pro-environmental behavior and subjective well-being, i.e., life satisfaction. METHODS: A longitudinal questionnaire survey consisting of two waves were conducted with Japanese respondents within an interval of 3 months (N = 770, mean age 49.6 ± 15.23 years). Correlation analyses and structural equation modeling were conducted to identify relationships between pro-environmental behavior and positive and negative psychological states and orientations. RESULTS: Results of both the two surveys indicated positive correlations of optimism-pessimism orientation (O/P ratio) and subjective well-being with pro-environmental behavior. Negative associations were also confirmed between depression, stress, and sleepiness and pro-environmental behavior. Structural equation modeling using the two-wave data revealed that O/P ratio is positively associated with pro-environmental behavior as longitudinal associations. CONCLUSIONS: These results suggest that O/P ratio can be related to current and future engagement in pro-environmental behavior and improvement in subjective well-being which could lead to an environmentally sustainable society with enhanced quality of life.

Hearing own or other's name has different effects on monotonous task performance.

We examined the effect of hearing two types of self-relevant words, one's own name and the name of others, on vigilant attention, arousal, and subjective sleepiness during performing the Psychomotor Vigilance Test (PVT). Participants performed the PVT under three experimental conditions, (a) hearing own full name (high self-relevant condition), (b) hearing other's name (low self- relevant condition) and (c) the control condition with no stimuli. Participants heard the names every 20 sec. Self-relevance was assessed before the experiment using the self-relevance scale. The results of the behavioral effects are relatively small and not consistently supported by all of the performance indicators. A tentative conclusion, based on the overall pattern of results, is that (1) arousal increased by hearing a name, regardless of its self-relevance, and (2) hearing less self-relevant stimuli such as other's name had a distractive effect on ongoing task performance, although it increased arousal, being aware that further experiments are urgently necessary.

Attentional lapses are reduced by repeated stimuli having own-name during a monotonous task.

The goal of the present study was to examine the effect of listening to self-relevant words (i.e., one's own name) on vigilant attention, arousal, and subjective sleepiness during performance of a psychomotor vigilance test (PVT). Twenty-one participants aged 20-26 years (22.2 ± 1.76) performed a PVT in four experimental conditions: one in which their own full name was pronounced every 20 s in the stimuli epochs, one in which their full name was pronounced in inverted form, one in which beeps were played, and a control condition with no stimuli. Listening to personal names reduced attentional lapses during the PVT (i.e., the number of reaction times no less than 500 ms). The results are a first step in applying the name effect to technologies and devices aimed at maintaining arousal levels and preventing accidents during a monotonous task, such as driving.

Interactive effects of visuomotor perturbation and an afternoon nap on performance and the flow experience.

The present study was designed (1) to clarify the relationship between the flow experience and improvements in visuomotor skills, (2) to examine the effects of rotating the axis of a computer mouse on visuomotor skills, and (3) to investigate the effects of sleep for improving visuomotor skills. Participants (N = 18) responded to Perturbation and nap (PER+Nap), No-perturbation and nap (NoPER+Nap) and Perturbation and rest (PER+Rest) conditions. In the PER+Nap condition, participants conducted a visuomotor tracking task using a computer mouse, which was accompanied by perturbation caused by rotating the axis of their mouse. After the task, they took a 90 min nap. In NoPER+Nap condition, they conducted the same visuomotor task without any perturbation and took a nap. In the PER+Rest condition, participants conducted the task with the perturbation and took a 90 min break spent reading magazines instead of taking a nap. Results indicated (1) the flow experience did not occur when participants' skills and the degree of the visuomotor challenge were matching, (2) improvements of visuomotor skills occurred regardless of the perturbation, (3) improvements of visuomotor skills occurred unrelated to the flow experience, or to mood states, and (4) improvements of visuomotor performance occurred regardless of sleep. These findings suggest that improvements of visuomotor skills occur regardless of mood status and occur independently of perturbations by axis rotation. The study also suggests that the acquisition of skills is related to merely the time elapsed since learning, rather than to sleep.

Safety and efficacy of treatment with liposomal amphotericin B in elderly patients at least 65 years old with hematological diseases.

The safety and efficacy of treatment with liposomal amphotericin B (L-AMB) in elderly patients has not been clarified, especially in Japanese patients. Therefore, we retrospectively analyzed 33 elderly patients with hematological diseases of at least 65 years old who received L-AMB between 2009 and 2012. Their clinical outcomes were compared to those of 21 patients who were younger than 65 years. L-AMB was administered for empirical therapy (n = 2) or target therapy for possible (n = 14) or probable/proven (n = 17) invasive fungal infection. There was no discontinuation of L-AMB due to adverse events. More than 2-fold increases from the baseline Cre, AST, and ALT values were observed in 21.2%, 39.4%, and 45.5% of the older group and 38.1%, 61.9%, and 52.4% of the younger group, respectively. The concurrent use of nephrotoxic antibiotics was the only risk factor for the development of a 2-fold increase in the serum Cre level. The duration of L-AMB was significantly longer in patients who developed grade III-IV hypokalemia. A partial or complete response was observed in 54.8% and 62.5% of the elderly and younger groups, respectively. In conclusion, L-AMB therapy appeared to be acceptably safe as empirical therapy or treatment for invasive fungal infection.

Role of sleep for encoding of emotional memory.

Total sleep deprivation (TSD) has been consistently found to impair encoding of information during ensuing wakefulness, probably through suppressing NonREM (non-rapid eye movement) sleep. However, a possible contribution of missing REM sleep to this encoding impairment after TSD has so far not been systematically examined in humans, although such contribution might be suspected in particular for emotional information. Here, in two separate experiments in young healthy men, we compared effects of TSD and of selective REM sleep deprivation (REMD), relative to respective control conditions of undisturbed sleep, on the subsequent encoding of neutral and emotional pictures. The pictures were presented in conjunction with colored frames to also assess related source memory. REMD was achieved by tones presented contingently upon initial signs of REM sleep. Encoding capabilities were examined in the evening (18:00h) after the experimental nights, by a picture recognition test right after encoding. TSD significantly decreased both the rate of correctly recognized pictures and of recalled frames associated with the pictures. The TSD effect was robust and translated into an impaired long term memory formation, as it was likewise observed on a second recognition testing one week after the encoding phase. Contrary to our expectation, REMD did not affect encoding in general, or particularly of emotional pictures. Also, REMD did not affect valence ratings of the encoded pictures. However, like TSD, REMD distinctly impaired vigilance at the time of encoding. Altogether, these findings indicate an importance of NonREM rather than REM sleep for the encoding of information that is independent of the emotionality of the materials.

Dopamine D2-like receptor activation wipes out preferential consolidation of high over low reward memories during human sleep.

Memory formation is a selective process in which reward contingencies determine which memory is maintained and which is forgotten. Sleep plays a pivotal role in maintaining information for the long term and has been shown to specifically benefit memories that are associated with reward. Key to memory consolidation during sleep is a neuronal reactivation of newly encoded representations. However, it is unclear whether preferential consolidation of memories associated with reward requires the reactivation of dopaminergic circuitry known to mediate reward effects at encoding. In a placebo-controlled, double-blind, balanced crossover experiment, we show that the dopamine D2-like receptor agonist pramipexole given during sleep wipes out reward contingencies. Before sleep, 16 men learned 160 pictures of landscapes and interiors that were associated with high or low rewards, if they were identified between new stimuli at retrieval 24 hr later. In the placebo condition, the participants retained significantly more pictures that promised a high reward. In the pramipexole condition, this difference was wiped out, and performance for the low reward pictures was as high as that for high reward pictures. Pramipexole did not generally enhance memory consolidation probably because of the fact that the dopaminergic agonist concurrently suppressed both SWS and REM sleep. These results are consistent with the concept that preferential consolidation of reward-associated memories relies on hippocampus-driven reactivation within the dopaminergic reward system during sleep, whereby during sleep reward contingencies are fed back to the hippocampus to strengthen specific memories, possibly, through dopaminergic facilitation of long-term potentiation.

Total sleep deprivation decreases flow experience and mood status.

BACKGROUND: The purpose of this study was to examine the effect of sleep deprivation on flow experience. METHODS: Sixteen healthy male volunteers of mean age 21.4±1.59 (21-24) years participated in two experimental conditions, ie, sleep-deprivation and normal sleep. In the sleep-deprived condition, participants stayed awake at home for 36 hours (from 8 am until 10 pm the next day) beginning on the day prior to an experimental day. In both conditions, participants carried out a simple reaction time (psychomotor vigilance) task and responded to a questionnaire measuring flow experience and mood status. RESULTS: Flow experience was reduced after one night of total sleep deprivation. Sleep loss also decreased positive mood, increased negative mood, and decreased psychomotor performance. CONCLUSION: Sleep deprivation has a strong impact on mental and behavioral states associated with the maintenance of flow, namely subjective well-being.

Can a short nap and bright light function as implicit learning and visual search enhancers?

The present study examined effects of a short nap (20 min) and/or bright light (2000 lux) on visual search and implicit learning in a contextual cueing task. Fifteen participants performed a contextual cueing task twice a day (1200-1330 h and 1430-1600 h) and scored subjective sleepiness before and after a short afternoon nap or a break period. Participants served a total of four experimental conditions (control, short nap, bright light and short nap with bright light). During the second task, bright light treatment (BLT) was applied in the two of the four conditions. Participants performed both tasks in a dimly lit environment except during the light treatment. Results showed that a short nap reduced subjective sleepiness and improved visual search time, but it did not affect implicit learning. Bright light reduced subjective sleepiness. A short nap in the afternoon could be a countermeasure against sleepiness and an enhancer for visual search. Practitioner Summary: The study examined effects of a short afternoon nap (20 min) and/or bright light (2000 lux) on visual search and implicit learning. A short nap is a powerful countermeasure against sleepiness compared to bright light exposure in the afternoon.

The relationship between flow, sleepiness and cognitive performance: the effects of short afternoon nap and bright light exposure.

"Flow" is a positive emotional state which typically occurs when a person perceives a balance between the challenges associated with a situation and his or her capabilities to accomplish these demands. While flow often occurs along with positive feelings and high introspective performance, only a few studies have investigated how it is associated with cognitive performance (i.e., objective performance). In the present study, we investigated the relationship between flow, emotions, and cognitive performance. A short nap (20 min) and bright light (>2,000 lux) techniques were used as experimental manipulations to enhance flow. Fifteen participants (31.3 ± 7.19 yr old) took part in four experimental conditions: rest, short nap, bright light, and nap and bright light. Pearson's correlation coefficients were calculated for flow and other indices using standardized data. Results showed that flow scores significantly increased after a short nap and under bright light exposure. The correlations between flow and reaction time were also significant. Flow was significantly associated with positive emotion and sleepiness. These results suggest that a short nap and bright light can be employed as a flow facilitator and that flow status can be used as an indicator in evaluating work efficiency and occupational mental health.

Use of subjective and physiological indicators of sleepiness to predict performance during a vigilance task.

Sleepiness is a major risk factor for serious injury and death in accidents. Although it is important to develop countermeasures to sleepiness to reduce risks, it is equally important to determine the most effective timing for these countermeasures. To determine optimum timing for necessary countermeasures, we must be able to predict performance errors. This study examined the predictability of subjective and physiological indicators of sleepiness during a vigilance task. Thirteen healthy male volunteers (mean age, 26.9 yr; SD = 5.98 yr; range 22-43 yr) participated in the study. Participants used the Karolinska sleepiness scale (KSS) to rate their subjective sleepiness every 4 min during a 40-min Mackworth clock test. Electrophysiological and performance data were divided into 10 epochs (i.e., 1 epoch lasted for 4 min). To estimate predictability, the data from the sleepiness indicators used for the correlation analysis were preceded by one epoch to the performance data. Results showed that sleepiness indicators (KSS score and electroencephalographic [EEG] alpha activity) and standard deviation of heart rate (SDNN) were significantly correlated with succeeding performance on the vigilance test. These findings suggest that the KSS score, EEG alpha activity, and SDNN could be used to predict performance errors.

The effects of asking for verbal ratings of sleepiness on sleepiness and its masking effects on performance.

OBJECTIVE: This study investigated whether verbal rating sleepiness will itself affect sleepiness and performance. METHODS: Thirteen healthy male volunteers (mean age, 26.9 years) performed two 40-min vigilance tests, one of which involved verbal ratings every 4min using the Karolinska sleepiness scale and another of which did not involve any ratings during the test. RESULTS: Repeated rating of sleepiness significantly reduced post-test sleepiness and improved the subjective perception of performance, and also reduced alpha power density (i.e., a physiological indicator of sleepiness). However, performance was not improved by the ratings. CONCLUSIONS: The act of rating affects subjective and EEG measures of sleepiness. Presumably this occurs through the modest stimulation involved in this act. SIGNIFICANCE: Methodologically one should be aware of subtle effects of the rating situation on sleepiness. From a practical point of view, it would be important for safety management since subjective sleepiness and performance are easily dissociated, which might interfere with risk perception.

Sickness absence in relation to psychosocial work factors among daytime workers in an electric equipment manufacturing company.

Associations between psychosocial work factors and sickness absence were investigated in a cross-sectional study of 833 daytime workers. Participants completed a questionnaire regarding psychosocial work factors using the US National Institute for Occupational Safety and Health Generic Job Stress Questionnaire (job control, quantitative workload, cognitive demands, variance in workload, intragroup conflict, intergroup conflict, supervisor support, coworker support, family support, job satisfaction and depressive symptoms) and the number of days of sickness absence within the previous year. Multivariate analyses of covariance with age and occupation as covariates (MANCOVA) were used to test the relationships between psychosocial work factors and sickness absence stratified by sex. In men, the age-adjusted MANCOVA showed that, quantitative workload was highest in the 0.5-4.5 d of sickness absence group (p<0.001). However, the levels of stress reactions (job satisfaction and depressive symptoms) in this group were almost identical to the levels recorded in the no sickness absence group. In contrast, low levels of job control (p<0.01), supervisor support (p<0.05), and job satisfaction (p<0.01) and higher symptoms of depression (p<0.001) were associated with 5 d or more sickness absence. In women, only high job satisfaction was associated with 5 d or more sickness absence (p<0.10). This study suggests that appropriate use of sickness absence at times of being exposed to high quantitative workload may help male workers to recover from stressful situations.

A short nap and natural bright light exposure improve positive mood status.

While the effects of a short nap on performance and arousal level have been well investigated, less attention has been paid to its effects on mood status. The aim of the present study was to examine the effects of a short nap and natural bright light exposure on mood status. Participants were 16 healthy females who were on average 38.1 (SD = 2.68) yr old. From 11:00 to 12:00, the participants carried out a set of tasks twice with baseline lighting (<100 lux). From 12:40 to 13:10, they were subjected to three experimental conditions: control (<100 lux), natural bright light (>2,000 lux), and a 20-min nap. From 13:10 to 16:10, the tasks were repeated six times with the baseline lighting. To measure mood status, multiple visual analogue scales (to measure anxiety, sadness, anger, confusion, apathy, fatigue, and sleepiness) and the Mood Check List 3 (MCL-3) (to derive "pleasantness", "satisfaction" and "relaxation") were employed. The results showed that brief (30 min) natural bright light exposure improved one dimension of mood status, "pleasantness". A short nap also improved dimensions of mood status ("pleasantness", "satisfaction", and "relaxation"). These results suggest that the proper application of both natural light and a short nap shifts the mood status to the positive/favorable side.