Functional Polymorphisms in Dopaminergic Genes Modulate Neurobehavioral and Neurophysiological Consequences of Sleep Deprivation

Penetrating Ballistic Brain Injury Produces Acute Alterations in Sleep and Circadian-Related Genes in the Rodent Cortex: A Preliminary Study

Traumatic brain injury (TBI) affects millions of Americans each year, with extremely high prevalence in the Veteran community, and sleep disturbance is one of the most commonly reported symptoms. Reduction in the quality and amount of sleep can negatively impact recovery and result in a wide range of behavioral and physiological symptoms, such as impaired cognition, mood and anxiety disorders, and cardiovascular effects. Thus, to improve long-term patient outcomes and develop novel treatments, it is essential to understand the molecular mechanisms involved in sleep disturbance following TBI. In this effort, we performed transcriptional profiling in an established rodent model of penetrating ballistic brain injury (PBBI) in conjunction with continuous sleep/wake EEG/EMG recording of the first 24 h after injury. Rats subjected to PBBI showed profound differences in sleep architecture. Injured animals spent significantly more time in slow wave sleep and less time in REM sleep compared to sham control animals. To identify PBBI-related transcriptional differences, we then performed transcriptome-wide gene expression profiling at 24 h post-injury, which identified a vast array of immune- related genes differentially expressed in the injured cortex as well as sleep-related genes. Further, transcriptional changes associated with total time spent in various sleep stages were identified. Such molecular changes may underlie the pathology and symptoms that emerge following TBI, including neurodegeneration, sleep disturbance, and mood disorders.

Genetics and Cognitive Vulnerability to Sleep Deprivation in Healthy Subjects: Interaction of ADORA2A, TNF-α and COMT Polymorphisms

Several genetic polymorphisms differentiate between healthy individuals who are more cognitively vulnerable or resistant during total sleep deprivation (TSD). Common metrics of cognitive functioning for classifying vulnerable and resilient individuals include the Psychomotor Vigilance Test (PVT), Go/noGo executive inhibition task, and subjective daytime sleepiness. We evaluated the influence of 14 single-nucleotide polymorphisms (SNPs) on cognitive responses during total sleep deprivation (continuous wakefulness for 38 h) in 47 healthy subjects (age 37.0 ± 1.1 years). SNPs selected after a literature review included SNPs of the adenosine-A2A receptor gene (including the most studied rs5751876), pro-inflammatory cytokines (TNF-α, IL1-β, IL-6), catechol-O-methyl-transferase (COMT), and PER3. Subjects performed a psychomotor vigilance test (PVT) and a Go/noGo-inhibition task, and completed the Karolinska Sleepiness Scale (KSS) every 6 h during TSD. For PVT lapses (reaction time >500 ms), an interaction between SNP and SDT (p < 0.05) was observed for ADORA2A (rs5751862 and rs2236624) and TNF-α (rs1800629). During TSD, carriers of the A allele for ADORA2A (rs5751862) and TNF-α were significantly more impaired for cognitive responses than their respective ancestral G/G genotypes. Carriers of the ancestral G/G genotype of ADORA2A rs5751862 were found to be very similar to the most resilient subjects for PVT lapses and Go/noGo commission errors. Carriers of the ancestral G/G genotype of COMT were close to the most vulnerable subjects. ADORA2A (rs5751862) was significantly associated with COMT (rs4680) (p = 0.001). In conclusion, we show that genetic polymorphisms in ADORA2A (rs5751862), TNF-α (rs1800629), and COMT (rs4680) are involved in creating profiles of high vulnerability or high resilience to sleep deprivation. (NCT03859882).

Clinical and Genetic Factors Associated With the Breast Cancer-Related Sleep Disorders: The "CAGE-Sleep" Study-A Cross-Sectional Study

CONTEXT

Despite being among the most reported concerns in breast cancer patients, sleep disturbances are still poorly assessed and managed in routine clinical practice. Correctly evaluating these symptoms and understanding the underlying clinical and genetic factors would help medical teams develop an adequate treatment strategy for each patient.

OBJECTIVES

1) To explore the severity of insomnia as well as sleep quality in a sample of Lebanese women with breast cancer undergoing chemotherapy; 2) To examine the correlation between sociodemographic, clinical, psychiatric (anxiety and depression), genetic factors, and alterations in sleep patterns.

METHODS

A cross-sectional study was carried out using the Pittsburgh Sleep Quality Index (PSQI) and Insomnia Severity Index (ISI) (December 2017-June 2019; Ethical reference number: CEHDF1016). All patients gave their written consent and were genotyped for several polymorphisms in CLOCK, CRY2, PER2, COMT, DRD2, OPRM1, and ABCB1 genes using Lightcycler® (Roche).

RESULTS

Our sample included a total of 112 women. Almost half of the patients reported insomnia problems (with 20.5% moderate insomnia and 7.1% severe insomnia). Multivariable analyses taking the PSQI score as the dependent variable, showed that higher depression score and dyslipidemia (yes versus no) were significantly associated with higher PSQI scores (worse sleep quality), whereas having the DRD2 CT genotype versus CC and a higher chemotherapy cycle number were significantly associated with lower PSQI scores (better sleep quality). Depression was also significantly associated with higher ISI scores. When forcing all the genes in each model, the results remained the same except for depression that has been replaced by anxiety in the multivariable analysis.

CONCLUSION

Our study confirms the relationship between anxiety/depression, cycle number, dyslipidemia and DRD2 polymorphism with insomnia and highlights the importance of treating all associated factors to improve the overall QOL of patients.

Genetic Markers of Differential Vulnerability to Sleep Loss in Adults

In this review, we discuss reports of genotype-dependent interindividual differences in phenotypic neurobehavioral responses to total sleep deprivation or sleep restriction. We highlight the importance of using the candidate gene approach to further elucidate differential resilience and vulnerability to sleep deprivation in humans, although we acknowledge that other omics techniques and genome-wide association studies can also offer insights into biomarkers of such vulnerability. Specifically, we discuss polymorphisms in adenosinergic genes (ADA and ADORA2A), core circadian clock genes (BHLHE41/DEC2 and PER3), genes related to cognitive development and functioning (BDNF and COMT), dopaminergic genes (DRD2 and DAT), and immune and clearance genes (AQP4, DQB1*0602, and TNFα) as potential genetic indicators of differential vulnerability to deficits induced by sleep loss. Additionally, we review the efficacy of several countermeasures for the neurobehavioral impairments induced by sleep loss, including banking sleep, recovery sleep, caffeine, and naps. The discovery of reliable, novel genetic markers of differential vulnerability to sleep loss has critical implications for future research involving predictors, countermeasures, and treatments in the field of sleep and circadian science.

Ischemic Stroke and Sleep: The Linking Genetic Factors

This review summarizes the available data about genetic factors which can link ischemic stroke and sleep. Sleep patterns (subjective and objective measures) are characterized by heritability and comprise up to 38-46%. According to Mendelian randomization analysis, genetic liability for short sleep duration and frequent insomnia symptoms is associated with ischemic stroke (predominantly of large artery subtype). The potential genetic links include variants of circadian genes, genes encoding components of neurotransmitter systems, common cardiovascular risk factors, as well as specific genetic factors related to certain sleep disorders.

Sleep-Wake Neurobiology

Sleep and wakefulness are complex, tightly regulated behaviors that occur in virtually all animals. With recent exciting developments in neuroscience methodologies such as optogenetics, chemogenetics, and cell-specific calcium imaging technology, researchers can advance our understanding of how discrete neuronal groups precisely modulate states of sleep and wakefulness. In this chapter, we provide an overview of key neurotransmitter systems, neurons, and circuits that regulate states of sleep and wakefulness. We also describe long-standing models for the regulation of sleep/wake and non-rapid eye movement/rapid eye movement cycling. We contrast previous knowledge derived from classic approaches such as brain stimulation, lesions, cFos expression, and single-unit recordings, with emerging data using the newest technologies. Our understanding of neural circuits underlying the regulation of sleep and wakefulness is rapidly evolving, and this knowledge is critical for our field to elucidate the enigmatic function(s) of sleep.

ADORA2A variation and adenosine A1 receptor availability in the human brain with a focus on anxiety-related brain regions: modulation by ADORA1 variation

Adenosine, its interacting A₁ and A_2A receptors, and particularly the variant rs5751876 in the A_2A gene ADORA2A have been shown to modulate anxiety, arousal, and sleep. In a pilot positron emission tomography (PET) study in healthy male subjects, we suggested an effect of rs5751876 on in vivo brain A₁ receptor (A₁AR) availability. As female sex and adenosinergic/dopaminergic interaction partners might have an impact on this rs5751876 effect on A₁AR availability, we aimed to (1) further investigate the pilot male-based findings in an independent, newly recruited cohort including women and (2) analyze potential modulation of this rs5751876 effect by additional adenosinergic/dopaminergic gene variation. Healthy volunteers (32/11 males/females) underwent phenotypic characterization including self-reported sleep and A₁AR-specific quantitative PET. Rs5751876 and 31 gene variants of adenosine A₁, A_2A, A_2B, and A₃ receptors, adenosine deaminase, and dopamine D₂ receptor were genotyped. Multivariate analysis revealed an rs5751876 effect on A₁AR availability (P = 0.047), post hoc confirmed in 30 of 31 brain regions (false discovery rate (FDR) corrected P values < 0.05), but statistically stronger in anxiety-related regions (e.g., amygdala, hippocampus). Additional effects of ADORA1 rs1874142 were identified; under its influence rs5751876 and rs5751876 × sleep had strengthened effects on A₁AR availability (P_both < 0.02; post hoc FDR-corrected Ps < 0.05 for 29/30 regions, respectively). Our results support the relationship between rs5751876 and A₁AR availability. Additional impact of rs1874142, together with rs5751876 and sleep, might be involved in regulating arousal and thus the development of mental disorders like anxiety disorders. The interplay of further detected suggestive ADORA2A × DRD2 interaction, however, necessitates larger future samples more comparable to magnetic resonance imaging (MRI)-based samples.

Newly identified sleep-wake and circadian circuits as potential therapeutic targets

Optogenetics and chemogenetics are powerful tools, allowing the specific activation or inhibition of targeted neuronal subpopulations. Application of these techniques to sleep and circadian research has resulted in the unveiling of several neuronal populations that are involved in sleep-wake control, and allowed a comprehensive interrogation of the circuitry through which these nodes are coordinated to orchestrate the sleep-wake cycle. In this review, we discuss six recently described sleep-wake and circadian circuits that show promise as therapeutic targets for sleep medicine. The parafacial zone (PZ) and the ventral tegmental area (VTA) are potential druggable targets for the treatment of insomnia. The brainstem circuit underlying rapid eye movement sleep behavior disorder (RBD) offers new possibilities for treating RBD and neurodegenerative synucleinopathies, whereas the parabrachial nucleus, as a nexus linking arousal state control and breathing, is a promising target for developing treatments for sleep apnea. Therapies that act upon the hypothalamic circuitry underlying the circadian regulation of aggression or the photic regulation of arousal and mood pathway carry enormous potential for helping to reduce the socioeconomic burden of neuropsychiatric and neurodegenerative disorders on society. Intriguingly, the development of chemogenetics as a therapeutic strategy is now well underway and such an approach has the capacity to lead to more focused and less invasive therapies for treating sleep-wake disorders and related comorbidities.

Risk of excessive sleepiness in sleep restriction therapy and cognitive behavioral therapy for insomnia: a randomized controlled trial

STUDY OBJECTIVES

Sleep restriction therapy (SRT) has been shown to be comparably effective relative to cognitive behavioral therapy for insomnia (CBT-I), but with lower requirements for patient contact. As such, SRT appears to be a viable alternate treatment for those who cannot complete a full course of CBT-I. However, it is unclear whether SRT-a treatment solely focusing on restricting time in bed-increases risk for sleepiness comparably to CBT-I. The current study tested objective sleepiness as an outcome in a randomized controlled trial comparing SRT, CBT-I, and attention control in a sample of postmenopausal women in whom insomnia was diagnosed according to criteria of the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition.

METHODS

Single-site, randomized controlled trial. A total of 150 postmenopausal women (56.44 ± 5.64 years) with perimenopausal or postmenopausal onset of Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition insomnia disorder were randomized to 3 treatment conditions: sleep education control (6 sessions); SRT (2 sessions with interim phone contact); and CBT-I (6 sessions). Blinded assessments were performed at pretreatment and posttreatment. Risk of excessive sleepiness was evaluated using a symmetry analysis of sleepiness measured through the Multiple Sleep Latency Test (MSLT).

RESULTS

The odds ratios (ORs) of being excessively sleepy versus nonsleepy were not different than 1.0 for both SRT (OR = 0.94, 95% confidence interval [0.13-6.96]) and CBT-I (OR = 0.62, 95% confidence interval [0.09-4.46]), indicating that the odds of becoming excessively sleepy following treatment was not different from the odds of being nonsleepy. This suggests that excessive sleepiness is not of unique concern following SRT relative to CBT-I or sleep education.

CONCLUSIONS

SRT appears to have a comparable risk profile for excessive sleepiness as CBT-I, and thus may be considered a safe alternative to CBT-I. Future research should characterize objective measures of excessive sleepiness immediately following sleep restriction.

CLINICAL TRAIL REGISTRATION

Registry: ClinicalTrials.gov; Name: Behavioral Treatment of Menopausal Insomnia; Sleep and Daytime Outcomes; Identifier: NCT01933295.

Sleep deprivation, vigilant attention, and brain function: a review

Vigilant attention is a major component of a wide range of cognitive performance tasks. Vigilant attention is impaired by sleep deprivation and restored after rest breaks and (more enduringly) after sleep. The temporal dynamics of vigilant attention deficits across hours and days are driven by physiologic, sleep regulatory processes-a sleep homeostatic process and a circadian process. There is also evidence of a slower, allostatic process, which modulates the sleep homeostatic setpoint across days and weeks and is responsible for cumulative deficits in vigilant attention across consecutive days of sleep restriction. There are large inter-individual differences in vulnerability to sleep loss, and these inter-individual differences constitute a pronounced human phenotype. However, this phenotype is multi-dimensional; vulnerability in terms of vigilant attention impairment can be dissociated from vulnerability in terms of other cognitive processes such as attentional control. The vigilance decrement, or time-on-task effect-a decline in performance across the duration of a vigilant attention task-is characterized by progressively increasing response variability, which is exacerbated by sleep loss. This variability, while crucial to understanding the impact of sleep deprivation on performance in safety-critical tasks, is not well explained by top-down regulatory mechanisms, such as the homeostatic and circadian processes. A bottom-up, neuronal pathway-dependent mechanism involving use-dependent, local sleep may be the main driver of response variability. This bottom-up mechanism may also explain the dissociation between cognitive processes with regard to trait vulnerability to sleep loss.

Association of DAT1 genetic variants with habitual sleep duration in the UK Biobank

Short sleep duration has been linked to negative health effects, but is a complex phenotype with many contributing factors, including genetic. We evaluated 27 common single nucleotide polymorphisms (SNPs) in candidate genes previously reported to be associated with other sleep variables for association with self-reported habitual sleep duration in the UK Biobank in 111 975 individuals of European ancestry. Genetic variation in DAT1 (rs464049) was significantly associated with sleep duration after correction for multiple testing (p = 4.00 × 10-5), whereas SNPs correlated to a previously studied variable number tandem repeat (VNTR) in DAT1 were not significant in this population. We also replicated a previously reported association in DRD2. Independent replication of these associations and a second signal in DRD2 (rs11214607) was observed in an additional 261 870 participants of European ancestry from the UK Biobank. Meta-analysis confirmed genome-wide significant association of DAT1 rs464049 (G, beta [standard error, SE] = -0.96 [0.18] minutes/allele, p = 5.71 × 10-10) and study-wide significant association of DRD2 (rs17601612, C, beta [SE] = -0.66 [0.18] minutes/allele, p = 1.77 × 10-5; rs11214607, C, beta [SE] = 1.08 (0.24) minutes/allele, p = 1.39 × 10-6). Overall, SNPs in two dopamine-related genes were significantly associated with sleep duration, highlighting the important link of the dopamine system with adult sleep duration in humans.

A dynamic attentional control framework for understanding sleep deprivation effects on cognition

The cognitive effects of sleep loss are often attributed to compromised functioning of the prefrontal cortex (PFC). However, compromised PFC functioning does not account for well-known effects of sleep deprivation on vigilance. Furthermore, the executive attentional control functions associated with the PFC show considerable variability in the effects of sleep deprivation. Evidence from neuroimaging suggests that sleep deprived people are sometimes able to maintain performance on cognitive tasks by increasing PFC activation of task-relevant circuits and by recruiting new circuits not typically involved in a particular cognitive operation. Still, little is known about how such compensatory processes work on a functional level, or what tradeoffs in processing they may entail. We propose a dynamic attentional control framework to bridge the gap between the evidence on sleep deprived neural circuits and cognitive task performance. We review evidence that shows that the pattern of preserved and compromised task performance can be understood in terms of sleep deprivation's influence on frontostriatal circuitry such that the ability to maintain task-relevant information in the focus of attention is relatively spared but the ability to update task-relevant information in response to changing circumstances is more negatively affected. This framework helps account for why some tasks are more affected by SD than others, and why individual differences in the effects of sleep deprivation are task-specific.

Clinical and Experimental Human Sleep-Wake Pharmacogenetics

Sleep and wakefulness are highly complex processes that are elegantly orchestrated by fine-tuned neurochemical changes among neuronal and non-neuronal ensembles, nuclei, and networks of the brain. Important neurotransmitters and neuromodulators regulating the circadian and homeostatic facets of sleep-wake physiology include melatonin, γ-aminobutyric acid, hypocretin, histamine, norepinephrine, serotonin, dopamine, and adenosine. Dysregulation of these neurochemical systems may cause sleep-wake disorders, which are commonly classified into insomnia disorder, parasomnias, circadian rhythm sleep-wake disorders, central disorders of hypersomnolence, sleep-related movement disorders, and sleep-related breathing disorders. Sleep-wake disorders can have far-reaching consequences on physical, mental, and social well-being and health and, thus, need be treated with effective and rational therapies. Apart from behavioral (e.g., cognitive behavioral therapy for insomnia), physiological (e.g., chronotherapy with bright light), and mechanical (e.g., continuous positive airway pressure treatment of obstructive sleep apnea) interventions, pharmacological treatments often are the first-line clinical option to improve disturbed sleep and wake states. Nevertheless, not all patients respond to pharmacotherapy in uniform and beneficial fashion, partly due to genetic differences. The improved understanding of the neurochemical mechanisms regulating sleep and wakefulness and the mode of action of sleep-wake therapeutics has provided a conceptual framework, to search for functional genetic variants modifying individual drug response phenotypes. This article will summarize the currently known genetic polymorphisms that modulate drug sensitivity and exposure, to partly determine individual responses to sleep-wake pharmacotherapy. In addition, a pharmacogenetic strategy will be outlined how based upon classical and opto-/chemogenetic strategies in animals, as well as human genetic associations, circuit mechanisms regulating sleep-wake functions in humans can be identified. As such, experimental human sleep-wake pharmacogenetics forms a bridge spanning basic research and clinical medicine and constitutes an essential step for the search and development of novel sleep-wake targets and therapeutics.

Dopamine and Wakefulness: Pharmacology, Genetics, and Circuitry

Over the period of decades in the mid to late twentieth century, arousal-promoting functions were attributed to neuromodulators including serotonin, hypocretin, histamine, and noradrenaline. For some time, a relatively minor role in regulating sleep and wake states was ascribed to dopamine and the dopamine-producing cells of the ventral tegmental area, despite the fact that dopaminergic signaling is a major target, if not the primary target, for wake-promoting agents. In recent years, due to observations from human genetic studies, pharmacogenetic studies in animal models, and the increasingly sophisticated methods used to manipulate the nervous systems of experimental animals, it has become clear that dopaminergic signaling is central to the regulation of arousal. This chapter reviews this central role of dopaminergic signaling, and in particular its antagonistic interaction with adenosinergic signaling, in maintaining vigilance and in the response to wake-promoting therapeutics.

Time-on-Task Effect During Sleep Deprivation in Healthy Young Adults Is Modulated by Dopamine Transporter Genotype

Study Objectives

The time-on-task (TOT) effect and total sleep deprivation (TSD) have similar effects on neurobehavioral functioning, including increased performance instability during tasks requiring sustained attention. The TOT effect is exacerbated by TSD, suggesting potentially overlapping mechanisms. We probed these mechanisms by investigating genotype-phenotype relationships on psychomotor vigilance test (PVT) performance for 3 a-priori selected genes previously linked to the TOT effect and/or TSD: dopamine active transporter 1 (DAT1), catechol-O-methyltransferase (COMT), and tumor necrosis factor alpha (TNFα).

Methods

N = 82 healthy adults participated in 1 of 3 laboratory studies. A 10-min PVT was administered repeatedly during 38 h of TSD. We assessed changes in response time (RT) across each minute of the PVT as a function of time awake and genotype. Additionally, cumulative relative RT frequency distributions were constructed to examine changes in performance from the first to the second 5 min of the PVT as a function of genotype.

Results

DAT1, COMT, and TNFα were associated with differences in the build-up of the TOT effect across the 10-min PVT. DAT1 additionally modulated the interaction between TSD and the TOT effect. Subjects homozygous for the DAT1 10-repeat allele were relatively protected against TOT deficits on the PVT during TSD compared to carriers of the 9-repeat allele.

Conclusions

DAT1 is known to regulate dopamine reuptake and is highly expressed in the striatum. Our results implicate striatal dopamine in mechanisms involved in performance instability that appear to be common to TSD and the TOT effect. Furthermore, DAT1 may be a candidate biomarker of resilience to the build-up of performance impairment across TOT due to TSD.

Effects of Chronic Intractable Insomnia on Inflammatory Cytokines, Blood Pressure Characteristics, and Antihypertensive Efficacy in Hypertensive Patients

BACKGROUND This study investigated the changes in blood pressure and inflammatory cytokines in patients with chronic intractable insomnia, and explored the effects of chronic intractable insomnia on antihypertensive efficacy. MATERIAL AND METHODS A total of 248 patients with hypertension admitted to our hospital from 2008 to 2017 were enrolled. We enrolled 124 patients without chronic insomnia in the control group, while 124 patients with chronic insomnia were included in the treatment group. The treatment group received estazolam and was further subdivided into the effective group (n=96) and the ineffective group (n=28) according to Sleep Dysfunction Rating Scale (SDRS) scores. Sleep quality before and after treatment was determined. RESULTS Antihypertensive treatment with eplerenone (50 mg) significantly reduced SDRS scores, C-reactive protein (CRP), tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), matrix metalloproteinase-9 (MMP-9), serum intercellular adhesion molecules (sICAM), and IL-1β levels, as well as systolic blood pressures (SBP) and diastolic blood pressures (DBP), with elevation of non-dipper blood pressure rhythm (P<0.05). The inhibition of intractable insomnia significantly downregulated SBP and DBP, as well as serum inflammatory cytokines such as CRP and TNF-α, showing a favorable effect on antihypertensive function. CONCLUSIONS Alleviation of chronic intractable insomnia facilitates hypertension therapy through decreasing levels of inflammatory cytokines and the proportion of non-dipper blood pressure rhythm, which offers insights for the treatment of hypertension.

Effects of COMT genotype and tolcapone on lapses of sustained attention after sleep deprivation in healthy young men

Tolcapone, a brain penetrant selective inhibitor of catechol-O-methyltransferase (COMT) devoid of psychostimulant properties, improves cognition and cortical information processing in rested volunteers, depending on the genotype of the functional Val158Met polymorphism of COMT. The impact of this common genetic variant on behavioral and neurophysiological markers of increased sleep need after sleep loss is controversial. Here we investigated the potential usefulness of tolcapone to mitigate consequences of sleep deprivation on lapses of sustained attention, and tested the hypothesis that dopamine signaling in the prefrontal cortex (PFC) causally contributes to neurobehavioral and neurophysiological markers of sleep homeostasis in humans. We first quantified in 73 young male volunteers the impact of COMT genotype on the evolution of attentional lapses during 40 h of extended wakefulness. Subsequently, we tested in an independent group of 30 young men whether selective inhibition of COMT activity with tolcapone counteracts attentional and neurophysiological markers of elevated sleep need in a genotype-dependent manner. Neither COMT genotype nor tolcapone affected brain electrical activity in wakefulness and sleep. By contrast, COMT genotype and tolcapone modulated the sleep loss-induced impairment of vigilant attention. More specifically, Val/Met heterozygotes produced twice as many lapses after a night without sleep than Met/Met homozygotes. Unexpectedly, tolcapone further deteriorated the sleep loss-induced performance deficits when compared to placebo, particularly in Val/Met and Met/Met genotypes. The findings suggest that PFC dopaminergic tone regulates sustained attention after sleep loss according to an inverse U-shape relationship, independently of neurophysiological markers of elevated sleep need.

Sleep Deprivation Diminishes Attentional Control Effectiveness and Impairs Flexible Adaptation to Changing Conditions

Insufficient sleep is a global public health problem resulting in catastrophic accidents, increased mortality, and hundreds of billions of dollars in lost productivity. Yet the effect of sleep deprivation (SD) on decision making and performance is often underestimated by fatigued individuals and is only beginning to be understood by scientists. The deleterious impact of SD is frequently attributed to lapses in vigilant attention, but this account fails to explain many SD-related problems, such as loss of situational awareness and perseveration. Using a laboratory study protocol, we show that SD individuals can maintain information in the focus of attention and anticipate likely correct responses, but their use of such a top-down attentional strategy is less effective at preventing errors caused by competing responses. Moreover, when the task environment requires flexibility, performance under SD suffers dramatically. The impairment in flexible shifting of attentional control we observed is distinct from lapses in vigilant attention, as corroborated by the specificity of the influence of a genetic biomarker, the dopaminergic polymorphism DRD2 C957T. Reduced effectiveness of top-down attentional control under SD, especially when conditions require flexibility, helps to explain maladaptive performance that is not readily explained by lapses in vigilant attention.