The effects of total sleep deprivation on semantic priming: Event-related potential evidence for automatic and controlled processing strategies

There is general consensus that performance on a number of cognitive tasks deteriorates following total sleep deprivation. At times, however, subjects manage to maintain performance. This may be because of an ability to switch cognitive strategies including the exertion of compensatory effort. The present study examines the effects of total sleep deprivation on a semantic word priming task. Word priming is unique because it can be carried out using different strategies involving either automatic, effortless or controlled, effortful processing. Twelve subjects were presented with word pairs, a prime and a target, that were either highly semantically associated (cat…dog), weakly associated (cow…barn) or unassociated (apple…road). In order to increase the probability of the use of controlled processing following normal sleep, the subject’s task was to determine if the target word was semantically related to the prime. Furthermore, the time between the offset of the prime and the onset of the target was relatively long, permitting the use of an effortful, expectancy-predictive strategy. Event-related potentials (ERPs) were recorded from 64 electrode sites. After normal sleep, RTs were faster and accuracy higher to highly associated targets; this performance advantage was also maintained following sleep deprivation. A large negative deflection, the N400, was larger to weakly associated and unassociated targets in both sleep-deprived and normal conditions. The overall N400 was however larger in the normal sleep condition. Moreover, a long-lasting negative slow wave developed between the offset of the prime and the onset of the target. These physiological measures are consistent with the use of an effortful, predictive strategy following normal sleep but an automatic, effortless strategy following total sleep deprivation. A picture priming task was also run. This task benefits less from the use of a predictive strategy. Accordingly, in this task, ERPs following the target did not differ as a function of the amount of sleep.     

New parents and driver safety: What’s sleep got to do with it? A systematic review

Fatigue-related motor vehicle crashes are common worldwide and have been addressed by a range of road safety campaigns. These campaigns are typically directed towards at-risk groups (e.g., heavy vehicle drivers), who may be likely to experience fatigue resulting from reduced or disrupted sleep opportunities. Another population likely to experience sleep loss and disruption is new parents. The sleep of new parents is likely to be significantly disrupted by childcare responsibilities. As such, new parents may also be likely to experience fatigue while driving. A systematic review of five databases (PubMed, Cumulative Index to Nursing and Allied Health Literature, PsycINFO, EMBASE, and the Cochrane Central Register of Controlled Trials) was performed to identify what research is currently available on sleep, fatigue, and driving in new parents. A total of twelve documents were included in this review. A synthesis of findings suggests new parents are at risk of fatigued driving – though the amount and quality of evidence available is limited. A research agenda is proposed to address the limitations of this field of research.     

What is the motor vehicle crash risk for drivers with a sleep disorder?

In many parts of the world, drivers with serious sleep disorders have restrictions on their licence – with the fitness-to-drive criteria varying across licensing jurisdictions. This study aimed to systematically review the literature that evaluated the available scientific evidence for the relationship between sleep disorders and two driving safety outcome measures: (i) motor vehicle crashes (MVC) and (ii) on-road driving test outcome. This review was registered with PROSPERO in July 2019 (see CRD42019144643). A systematic search of public health, psychology and transport databases was conducted on November 8th, 2019. The quality of evidence for each study was rated using the National Heart, Lung and Blood Institute Quality Assessment tools. Thirty-nine studies published between 1976 and 2015 met the inclusion criteria (n = 9 case-control; n = 24 cohort/cross-sectional; n = 6 before-after). Overall, the quality of evidence for 22 studies was rated as ‘good’, nine as ‘fair’ and eight as ‘poor’. Included studies addressed: sleep apnoea and sleep-related breathing disorders (n = 35); central disorders of hypersomnolence and narcolepsy (n = 5), and insomnia (n = 2), with some studies covering multiple sleep disorders. Of the thirty-five studies specifically investigating MVC risk associated with sleep apnoea, eighteen studies reported an increased risk (n = 11 ‘good’, n = 4 ‘fair’, n = 3 ‘poor’ quality), seven reported no difference in risk (n = 3 ‘good’, n = 4 ‘fair’ quality), and two provided inconclusive findings (n = 1 ‘good’, n = 1 ‘fair’ quality). Most studies suggested that increased sleep apnoea severity was associated with an increased MVC risk. Furthermore, untreated sleep apnoea was predominantly associated with increased risk, whilst decreased risk was associated with Continuous Positive Airway Pressure (CPAP) and uvulopalatopharyngoplasty (UPPP) treatments. Five studies (n = 3 ‘good’, n = 2 ‘fair’ quality) investigated MVC risk associated with disorders of hypersomnolence and narcolepsy, and all reported increased risk. Only two studies investigated MVC risk associated with insomnia, with inconsistent findings: one reporting increased MVC risk (‘good’) and one reporting no difference (‘fair’). Regarding impacts on on-road driving test outcome, our comprehensive search found no studies investigating the association between sleep disorders and this driving safety outcome measure. Notwithstanding the limitations of the included studies, the weight of evidence suggests a moderately elevated MVC risk for drivers with sleep disorders (sleep apnoea; hypersomnia and narcolepsy), with the majority reporting around two and a half times higher risk, and lower risk with treatment. This evidence is consistent with current fitness-to-drive guidelines, most of which specify licence restrictions conditional upon severity, treatment compliance and effective response to treatment. The generalisability of the findings is limited as many identified studies had methodological limitations, were conducted across a wide time period, in numerous licensing jurisdictions with different requirements, and across a diverse range of participant populations. A large-scale, population-based controlled study, in multiple licensing jurisdictions with equivalent licensing and fitness-to-drive requirements, is warranted to rigorously investigate MVC risk and sleep disorders, including evaluating the possible benefit of therapies.     

Islands of memory: Autobiographical remembering in amnestics

In amnestics with anterograde amnesia, memories of post-onset autobiographical experiences, if present at all, are typically barren and impoverished. However, there have been sporadic reports of islands of memory—memories that are vivid, detailed, and specific to time and place. The aim of this study was to verify the presence of such memories and examine their incidence rate. Anterograde amnestics were interviewed in their home using a narrative interviewing strategy with a view to describing memory in everyday life. Each autobiographical memory of a post-onset event was coded for quantity-length, and quality-episodicity. In just over half of the amnestics (8 out of 14), a memory that was lengthy, rich in personal details, and localisable was recollected. The quantitative and qualitative aspects of these island memories were significantly different from the other autobiographical memories that the amnestics supplied. These memories were at odds with what would be expected on the basis of their performance on standardised memory instruments. Our findings suggest there is occasionally more variability in remembering of autobiographical experiences in some amnestics than has traditionally been believed.     

Retrieval-induced forgetting,delay, and sleep

Retrieval-induced forgetting (RIF) refers to the finding that retrieval of a subset of previously studied material can cause forgetting of related unpractised material. Prior work on the role of delay between practice and test for RIF reported mixed results. Whereas some studies found RIF to be a relatively transient phenomenon, others found RIF to persist over time. We examined whether the persistence of RIF can depend on whether wakefulness or sleep follows retrieval practice. We employed a variant of the retrieval-practice paradigm with short (20 minutes) and long (12 hours) delay conditions. In all conditions participants studied a perceptually categorised list followed by retrieval practice on some of the items from some of the categories. Participants studied and practised the material in the morning or the evening. RIF was present in the short-delay conditions, and it was present in the long-delay condition if the delay included nocturnal sleep; if the long delay was filled with diurnal wakefulness, RIF was absent. Results show that whether delay eliminates RIF or not can depend on whether sleep or wake follows retrieval practice. Connections of the results to recent findings about the role of delay and sleep for RIF are discussed.     

One night of sleep is insufficient to achieve sleep-to-forget emotional decontextualisation processes

Neutral memories unbind from their emotional acquisition context when sleep is allowed the night after learning and testing takes place after two additional nights of sleep. However, mood-dependent memory (MDM) effects are not abolished after a restricted sleep episode mostly featuring non rapid-eye-movement (NREM) or rapid-eye-movement (REM) sleep. Here, we tested whether (1) one night of sleep featuring several NREM-REM sleep cycles is sufficient to suppress MDM effects and (2) a neutral mood is a sufficiently contrasting state to induce MDM effects, i.e. interfere with the recall of information learned in happy or sad states. Results disclosed MDM effects both in the post-learning sleep and wake conditions, with better recall in congruent than incongruent emotional contexts. Our findings suggest that the emotional unbinding needs several consecutive nights of sleep to be complete, and that even subtle mood changes are sufficient to produce MDM effects.     

The Chronotype-Academic Performance Model (CAM): Daytime sleepiness and learning motivation link chronotype and school performance in adolescents

Many adolescents experience a discrepancy between their biological time, which is shifted toward eveningness, and early school starting times. Due to this social jetlag, eveningness is negatively correlated with school performance. On the basis of the here presented data, we derived a model for the association of chronotype and school performance, the Chronotype-Academic Performance Model (CAM), including daytime sleepiness and achievement motivation as mediating factors. The sample comprised N = 273 adolescents aged 14–16 years. Circadian preference, daytime sleepiness, learning and achievement motivation, and information about participants’ last school certificate were assessed online. Chronotype was not directly related to academic performance, but was mediated by daytime sleepiness and learning motivation. Morning-orientation was negatively associated with daytime sleepiness and positively with learning motivation, which, in turn, affected performance. In evening-types, we found the strongest association between sleepiness and refusal to work. The CAM suggests that chronotype may not directly influence academic performance, but be mediated by daytime sleepiness and learning motivation. Evening types seem to be at high risk to suffer from daytime sleepiness and to display dysfunctional attitudes toward work. Measures of reducing sleepiness and modifying attitudes toward academic achievement might attenuate the disadvantages of evening-types due to social jetlag.     

A self-help book is better than sleep hygiene advice for insomnia: a randomized controlled comparative study

The objective was to compare the effects of two types of written material for insomnia in a randomized trial with follow-up after three months. Insomniacs were recruited through newspaper advertisements to a web-based survey with validated questionnaires about sleep, anxiety, depression, and use of sleep medications. A self-help book focusing on cognitive behavioral therapy for insomnia was compared to standard sleep hygiene advice; 77 and 78 participants were randomized to self-help book or sleep hygiene advice, respectively. The response rate was 81.9%. The self-help book gave significantly better scores on the sleep questionnaires compared to sleep hygiene advice. The proportion using sleep medications was reduced in the self-help book group, whereas it was increased in the sleep hygiene group. Compared to pre-treatment, the self-help book improved scores on the sleep (effect sizes 0.61-0.62) and depression (effect size 0.18) scales, whereas the sleep hygiene advice improved scores on some sleep scales (effect sizes 0.24-0.28), but worsened another (effect size -0.36). In addition, sleep hygiene advice increased the number of days per week where they took sleep medications (effect size -0.50). To conclude, in this randomized controlled trial, the self-help book improved sleep and reduced the proportion using sleep medications compared to sleep hygiene advice. The self-help book is an efficient low-threshold intervention, which is cheap and easily available for patients suffering from insomnia. Sleep hygiene advice also improved sleep at follow-up, but increased sleep medication use. Thus, caution is warranted when sleep hygiene advice are given as a single treatment.     

Chronicity and severity of maternal postpartum depression and infant sleep disorders: a population-based cohort study in southern Brazil

A cohort study was conducted with 397 women randomly selected from the Brazilian National System of Public Health, to describe the prevalence rates of infant sleep problems at 12-month of life, and its association with chronicity and severity of maternal depressive symptoms. Mothers were assessed, first, from the 9th to the 12th week postpartum and then at 12 months after delivery, with EPDS and a self-rating questionnaire regarding babies’ sleep behavior. After controlling for possible confounders, babies whose mothers had severe chronic depressive symptoms were at higher risk for sleep disorder at 12 months of birth.     

Motor interference does not impair the memory consolidation of imagined movements

The present study aimed to investigate whether an interference task might impact the sleep-dependent consolidation process of a mentally learned sequence of movements. Thirty-two participants were subjected to a first training session through motor imagery (MI) or physical practice (PP) of a finger sequence learning task. After 2 h, half of the participants were requested to perform a second interfering PP task (reversed finger sequence). All participants were finally re-tested following a night of sleep on the first finger sequence. The main findings revealed delayed performance gains following a night of sleep in the MI group, i.e. the interfering task did not alter the consolidation process, by contrast to the PP group. These results confirm that MI practice might result in less retroactive interference than PP, and further highlight the relevance of the first night of sleep for the consolidation process following MI practice. These data might thus contribute to determine in greater details the practical implications of mental training in motor learning and rehabilitation.