Sleep deprivation affects multiple distinct cognitive processes

Adaptation of a sleep hygiene intervention for individuals with poor sleep and their companions: Results of a randomized controlled pilot trial

Sleep is a major health issue for young adults. While sleep hygiene interventions have small-to-moderate effects, better outcomes might be achieved by delivering interventions individually to those reporting sleep difficulties, or in the presence of a supportive other or companion. To examine the feasibility, acceptability, and initial effects of an adapted sleep hygiene intervention for young adults with poor sleep, we conducted an ORBIT Phase IIb pilot randomized controlled trial (n = 51). Young adults with poor sleep were randomized to receive a sleep hygiene intervention individually or with a companion. Sleep patterns were measured at baseline and 4 weeks. Participants completed daily dairies and wore wearable devices for the month following the intervention. Attrition at follow-up was minimal (3.9%), and missing rates were low for diary data (8%), and in line with prior studies for wearable devices (14%). Participants expressed high levels of satisfaction with the study, with no differences between study arms. Significant effects were found postintervention for all participants, indicating improved sleep quality (t = 6.14, P < .001), greater sleep duration (t = 3.8, P < .001), and reduced daytime sleepiness (t = 2.13, P = .039). There were no significant differences in sleep efficiency pre and postintervention, or between study arms for any sleep outcome based on self-reported and objective data. Results from this pilot provide evidence for the feasibility and acceptability of a sleep hygiene intervention for young adults and lay the groundwork for a larger, fully powered study.

Psychosocial Factors, Sleep, and Central Pain Processing for Making a Prognosis About Recovery of Pain, Function, and Quality of Life After Rotator Cuff Repair: An Exploratory Longitudinal Study

OBJECTIVE: To explore modifiable psychosocial factors, sleep-related variables, indices of central pain processing and patients' characteristics as potential prognostic factors for pain, shoulder function, and quality of life (QoL) 1 year after rotator cuff repair. DESIGN: This observational longitudinal study included 142 patients who were undergoing rotator cuff repair. All measures took place pre-rotator cuff repair (T0), and 12 weeks (T1) and 12 months (T2) after rotator cuff repair. METHODS: Mixed-effects linear regression modeled relationships between the Western Ontario Rotator Cuff Index (WORC, model A), the Subjective Shoulder Value (SSV, model B), and EuroQol's EQ-5D-5L for QoL (model C), and potential prognostic factors over time. Factors included psychosocial variables, sleep-related indices, and proxies of central pain processing. Patients' age, sex, and body mass index complemented the analyses. RESULTS: At follow-up (T2), data from 124 participants were available for analysis. Five prognostic factors were identified for the 1-year outcome. Better expectations for symptom reduction (P<.0001, -1.4 mm) and an increase in Douleur Neuropathique 4 score (P = .0481, -0.9 mm) affected the evolution of WORC over time (model A). An increase in injury perception subscale consequence (P = .0035, 0.04%) influenced the SSV trajectory (model B). In addition, when sleep quality (P = .0011, -0.13%) and sleep efficiency (P = .0002, 0.005%) improved, the EQ-5D-5L slope was affected (model C). CONCLUSION: Addressing cognitions, pain mechanisms and sleep behavior prior to rotator cuff repair can identify people who are at risk of a poor outcome after surgery. J Orthop Sports Phys Ther 2024;54(8):530-540. Epub 4 July 2024. doi:10.2519/jospt.2024.12398.

Specificity and sensitivity of the fixed-point test for binary mixture distributions

When two cognitive processes contribute to a behavioral output-each process producing a specific distribution of the behavioral variable of interest-and when the mixture proportion of these two processes varies as a function of an experimental condition, a common density point should be present in the observed distributions of the data across said conditions. In principle, one can statistically test for the presence (or absence) of a fixed point in experimental data to provide evidence in favor of (or against) the presence of a mixture of processes, whose proportions are affected by an experimental manipulation. In this paper, we provide an empirical diagnostic of this test to detect a mixture of processes. We do so using resampling of real experimental data under different scenarios, which mimic variations in the experimental design suspected to affect the sensitivity and specificity of the fixed-point test (i.e., mixture proportion, time on task, and sample size). Resampling such scenarios with real data allows us to preserve important features of data which are typically observed in real experiments while maintaining tight control over the properties of the resampled scenarios. This is of particular relevance considering such stringent assumptions underlying the fixed-point test. With this paper, we ultimately aim at validating the fixed-point property of binary mixture data and at providing some performance metrics to researchers aiming at testing the fixed-point property on their experimental data.

The effect of total sleep deprivation on working memory: evidence from diffusion model

STUDY OBJECTIVES

Working memory is crucial in human daily life and is vulnerable to sleep loss. The current study investigated the impact of sleep deprivation on working memory from the information processing perspective, to explore whether sleep deprivation affects the working memory via impairing information manipulation.

METHODS

Thirty-seven healthy adults attended two counterbalanced protocols: a normal sleep night and a total sleep deprivation (TSD). The N-back and the psychomotor vigilance task (PVT) assessed working memory and sustained attention. Response time distribution and drift-diffusion model analyses were applied to explore cognitive process alterations.

RESULTS

TSD increased the loading effect of accuracy, but not the loading effect of response time in the N-back task. TSD reduced the speed of information accumulation, increased the variability of the speed of accumulation, and elevated the decision threshold only in 1-back task. Moreover, the slow responses of PVT and N-back were severely impaired after TSD, mainly due to increased information accumulation variability.

CONCLUSIONS

The present study provides a new perspective to investigate behavioral performance by using response time distribution and drift-diffusion models, revealing that sleep deprivation affected multicognitive processes underlying working memory, especially information accumulation processes.

Effect of homeostatic pressure and circadian rhythm on the task-switching: Evidence from drift diffusion model and ERP

The effect of diurnal fluctuations on cognitive functions is widely studied, yet rare research has attempted to separate the role of two crucial processes underlying diurnal fluctuations: homeostatic pressure and circadian rhythm. The present study aimed to dissociate their effects by conducting a task-switching task in the morning, napping afternoon, and no-napping afternoon, respectively. Additionally, DDM and ERP were utilized to explore how these two processes differentially affect cognitive processes involved in task-switching. By a within-participant design, 35 healthy adults (20.03 ± 2.01 year-old, 14 males) with an intermediate-type chronotype were recruited in the current study. The results demonstrated that accumulated homeostatic pressure caused reduced accuracy, drift rate, and decision threshold. In the no-napping afternoon, P1 and P2 amplitudes were also decreased due to homeostatic pressure, whereas an afternoon nap could partially restore performance and neural activity. Conversely, the upward circadian rhythm in the afternoon exerted a compensatory effect, resulting in increases in N2 and P3 amplitudes. The findings highlight the disassociated impacts of homeostatic pressure and circadian rhythm on the cognitive processes involved in task-switching and further underscore the importance of considering diurnal variation in both scientific research and accident prevention.

Time-of-day effects on speed and accuracy performance during simulated shiftwork

Performance on tasks involving speed and accuracy fluctuate throughout the 24-h day negatively affecting shift workers and organizations. Two simulated work shifts common in occupational settings were used to assess performance on a vigilance and math task. In study 1, 33 sleep-deprived participants completed a nightshift. In study 2, 32 partially sleep-deprived participants completed a dayshift. These studies found that performance differed between the type of task and the type of simulated shift where performance during the nightshift was worse than during the dayshift. In addition, collapsing speed and accuracy on the math task into inverse efficiency scores provided a unique measure that captured the impact of circadian rhythms during shiftwork. The current study also indicated that participants adopted cognitive strategies including speed-accuracy tradeoff and regulatory foci regarding work motivation (prevention focus and promotion focus) when completing the tasks depending on time-of-day, type of shift, circadian rhythms, and amount of sleep deprivation. This suggests that researchers and organizations should consider cognitive strategies in addition to the physiological components of sleep deprivation and circadian rhythms when investigating and documenting the impact of time-of-day due to different types of shiftwork conditions on performance and safety.

Effect of fear of missing out on learning burnout in medical students: a moderated mediation

Introduction

Learning burnout has a significant negative impact on students' academic performance and professional development, which has been exacerbated by the growing trend of problematic smartphone use, such as smartphone addiction, among young people. Recently, the literature on excessive social media use has revealed a critical role of fear of missing out. Objective The purpose of this study was to examine how fear of missing out affects smartphone addiction and its subsequent effect on learning burnout in college students.

Methods

In Study 1, 352 medical students were recruited to complete a cross-sectional survey. In Study 2, 2,948 college students were recruited to complete a cross-sectional survey. Further in Study 3, 30 medical students were recruited into a mindfulness-based intervention program.

Results

Study 1 preliminarily confirmed that fear of missing out was positively correlated with learning burnout. Study 2 then revealed a moderated mediation model showing that fear of missing out may increase smartphone addiction, which in turn affects their sleep quality and finally leads to learning burnout. This chain mediation model was moderated by the participants' level of mindfulness. To confirm the promoting role of mindfulness, Study 3 further confirmed that mindfulness training indeed can improve smartphone addiction and reduce learning burnout in medical students.

Discussion

Theoretical and practical contributions were discussed, highlighting the effects of fear of missing out on smartphone addiction and a moderating role of mindfulness training.

A spatially continuous diffusion model of visual working memory

We present results from five visual working memory (VWM) experiments in which participants were briefly shown between 2 and 6 colored squares. They were then cued to recall the color of one of the squares and they responded by choosing the color on a continuous color wheel. The experiments provided response proportions and response time (RT) measures as a function of angle for the choices. Current VWM models for this task include discrete models that assume an item is either within working memory or not and resource models that assume that memory strength varies as a function of the number of items. Because these models do not include processes that allow them to account for RT data, we implemented them within the spatially continuous diffusion model (SCDM, Ratcliff, 2018) and use the experimental data to evaluate these combined models. In the SCDM, evidence retrieved from memory is represented as a spatially continuous normal distribution and this drives the decision process until a criterion (represented as a 1-D line) is reached, which produces a decision. Noise in the accumulation process is represented by continuous Gaussian process noise over spatial position. The models that fit best from the discrete and resource-based classes converged on a common model that had a guessing component and that allowed the height of the normal memory-strength distribution to vary with number of items. The guessing component was implemented as a regular decision process driven by a flat evidence distribution, a zero-drift process. The combination of choice and RT data allows models that were not identifiable based on choice data alone to be discriminated.

Association of Academic Stress, Acne Symptoms and Other Physical Symptoms in Medical Students of King Khalid University

Academic stress has varied effects on medical student life due to multiple factors, like study load, competition, frequent assessment, social pressure, etc. The authors of this paper conducted research to find the academic stress level and its sequel over acne and other physical symptoms on the medical students of King Khalid University (KKU), Saudi Arabia. A total of 168 participant responses were analyzed. Data collection was performed using a self-administered online questionnaire through the university website portal. The study tool was comprised of four sections: demographic characteristics, academic stress, acne symptoms, and other physical symptoms. Statistical analysis was performed using SPSS software. A high proportion of females (88.7%) participated in the study. Upon categorization of overall academic stress, it was found that a majority of the medical students were moderately stressed (58.34%). The response on the academic stress scale revealed that exams are the major cause of stress among students. The Mean ± SD of academic stress, acne symptoms, and physical symptoms differ significantly at <0.01 level of significance. Overall academic stress showed a significant positive association with acne (<0.01) and physical symptoms (<0.01). The strength of this study is the fact that its categorization of stress caused by academics has not been done elsewhere. In addition, the impact of acne and physical symptoms has not been found in recent literature. Keeping the outcome of the present study in mind, it is suggested to arrange timely counselling sessions in medical colleges which can alert medical students to remain conscious about the consequences of stress.

The Common Effects of Sleep Deprivation on Human Long-Term Memory and Cognitive Control Processes

Sleep deprivation is known to have adverse effects on various cognitive abilities. In particular, a lack of sleep has been reported to disrupt memory consolidation and cognitive control functions. Here, focusing on long-term memory and cognitive control processes, we review the consistency and reliability of the results of previous studies of sleep deprivation effects on behavioral performance with variations in the types of stimuli and tasks. Moreover, we examine neural response changes related to these behavioral changes induced by sleep deprivation based on human fMRI studies to determine the brain regions in which neural responses increase or decrease as a consequence of sleep deprivation. Additionally, we discuss about the possibility that light as an environmentally influential factor affects our sleep cycles and related cognitive processes.

Assessment of Insomnia Symptoms, Quality of Life, Daytime Sleepiness, and Psychoactive Substance Use among Polish Students: A Cross-Sectional Online Survey for Years 2016–2021 before and during COVID-19 Pandemic

Sleep disorders are a serious health problem worldwide, and insomnia is their most common manifestation. An increasing number of people have insomnia every year, young adults, especially. Due to the importance that sleep has in almost every aspect of our lives, the need to monitor disturbances in circadian rhythms has arisen. Therefore, this study aimed to assess the prevalence of sleep disorders among Polish students, including their quality of life (QOL) and drug use patterns. The study also investigated associations between sleep, QoL, and drug use. The study was conducted in 2016–2021 based on the self-made sociodemographic questionnaire, as well as standardized psychometric tools: Athens Insomnia Scale (AIS), Epworth Sleepiness Scale (ESS), and Manchester Short Assessment of quality of life (MANSA). A total of 14,844 students participated in the study. The majority were women (80.7%), of which 3425 (23.1%) were medical students, with the most numerous representing medical and dental faculties, 1884 (57.2%). Before the COVID-19 pandemic, 52.1% of the surveys were collected; 54.1% of respondents had insomnia as indicated by the AIS scores, and 26.1% displayed sleepiness during the day. Female students, the first-year college students, more often suffered from sleep disorders. Drug use was widespread among Polish students, correlating with sleep assessment results and QoL. In conclusion, sleep disorders are a significant clinical problem among Polish students. Female and junior students’ years are more prone to sleep deprivation. Insufficient sleep can be associated with a lower QoL score and psychoactive substance use. The effects of the COVID-19 pandemic on sleep are not conclusive, because there was decreasing quality for longer sleep durations. In order to analyze these associations, there is a need for further in-depth study.

Nighttime Sleep Awakening Frequency and Its Consistency Predict Future Academic Performance in College Students

Although the relationship between sleep and academic performance has been extensively examined, how sleep predicts future academic performance (e.g., 2-3 years) remains to be further investigated. Using wearable smartwatches and a self-report questionnaire, we tracked sleep activities of 45 college students over a period of approximately half a month to see whether their sleep activities predicted their academic performance, which was estimated by grade point average (GPA). Results showed that both nighttime sleep awakening frequency and its consistency in the tracking period were not significantly correlated with the GPA for the courses taken in the sleep tracking semester (current GPA). However, both nighttime sleep awakening frequency and its consistency inversely predicted the GPA for the rest of the courses taken after that semester (future GPA). Moreover, students with more difficulty staying awake throughout the day obtained lower current and future GPAs, and students with higher inconsistency of sleep quality obtained lower future GPA. Together, these findings highlight the importance of nighttime sleep awakening frequency and consistency in predicting future academic performance, and emphasize the necessity of assessing the consistency of sleep measures in future studies.

Sleep quality and its correlates among undergraduate medical students in Nepal: A cross-sectional study

Poor sleep quality has been found to affect students' learning abilities, academic performance, and interpersonal relationships. However, little is known about this issue in Nepal. This study aimed to identify the factors associated with poor sleep quality among undergraduate medical students in Nepal. A web-based survey was conducted in March 2021 among 212 undergraduate medical students at the Institute of Medicine, Kathmandu, Nepal. Sleep quality was measured using a 19-item Pittsburgh Sleep Quality Index (PSQI). Multivariable logistic regression analysis was done to assess the factors associated with sleep quality. In the study participants, 38.2% of the students were identified as poor sleepers. Factors like being depressed (AOR = 4.5, 95% CI; 1.2-5.4), current alcohol use (AOR = 2.5, 95% CI; 1.8-10.8), poor academic achievement (AOR = 3.4, 95% CI; 1.1-10.9), and being a fourth-year student (AOR = 3.6, 95% CI; 1.1-11.8) were significantly associated with poor sleep quality. Poor sleep quality was common among undergraduate medical students. Routine screening of sleep quality and depressive symptoms is necessary to mitigate their impact among medical students. Medical students of the fourth year, current alcohol users, and those who did not have good academic achievement had poor sleep quality. Special attention on these population subgroups is thus needed to enhance sleep quality.

Association Between Sleep Disorders and Cognitive Impairment in Middle Age and Older Adult Hemodialysis Patients: A Cross-Sectional Study

Objective: The aims of the current study were to (1) explore the features of overall poor sleep and specific sleep disorders in Chinese middle age and older adult hemodialysis patients; (2) examine the association between sleep disorders and cognitive impairment (CI) in middle age and older patients undergoing hemodialysis in China.

Methods: Data of patients undergoing maintenance hemodialysis were collected from the prospective cohort study of CI in Chinese patients undergoing hemodialysis (Registered in Clinical Trials.gov, ID: NCT03251573). We included 613 patients (mean age = 63.7; SD = 7.8) in this study. We assessed sleep conditions using the Pittsburgh Sleep Quality Index (PSQI) questionnaire and cognitive function by the Chinese Beijing version of the Montreal Cognitive Assessment (MoCA-BJ) scale. Then the association between sleep disorders and CI was evaluated using multivariate logistic regression analysis.

Results: The prevalence of sleep disorders in this group of 613 hemodialysis patients was 77.0%. Patients with CI were more inclined to have sleep disorders in specific aspects of sleep latency, habitual sleep efficiency, sleep disturbances, and daytime dysfunction (p < 0.05). In multivariate logistic regression analyses, every 1-point increase in global PSQI score was associated with a 1.2-fold increased risk of CI (adjusted OR = 1.201; 95%CI = 1.123–1.284, p < 0.001). For each specific PSQI, every 1-point increase in sleep disturbances score was associated with a 2.6-fold increased risk of CI (adjusted OR = 2.624; 95%CI = 1.891–3.640, p < 0.001), and every 1-point increase in daytime dysfunction score was associated with a 3.7-fold increased risk of CI (adjusted OR = 3.709; 95%CI = 2.653–5.184, p < 0.001), whereas every 1-point increase in sleep duration score was associated with a decreased risk of CI (adjusted OR = 0.600; 95%CI = 0.434–0.830, p = 0.002).

Conclusion: Poor sleep quality especially sleep disturbances, daytime dysfunction, and long sleep duration are associated with CI in middle age and older adult hemodialysis patients. Thus, the early detection of sleep disorders may help identify patients with cognitive impairment among hemodialysis individuals.

Clinical Trial Registration: [Clinical Trials.gov], identifier [NCT03251573]

Transcranial direct current stimulation (tDCS) alters the pattern of information processing in children with ADHD: Evidence from drift diffusion modeling

OBJECTIVE

Performance accuracy and reaction time in cognitive tasks are routinely used to evaluate the efficacy of tDCS to affect cognitive task performance. tDCS alters the excitability of targeted brain areas and thereby alters performance of cognitive tasks. The drift diffusion model (DDM) provides some additional measures to explore information processing style, such as (non)decision time, bias for decision, and speed of information processing. DDM parameters are informative for the study of cognitive impairments in children with ADHD. In the present study, we aimed to evaluate the impact of tDCS on cognitive performance via DDM measures.

METHODS

This study conducted DDM modeling and reanalysis of two exploratory, single-blinded, within-subject design experiments, which were published earlier. In the first experiment, twenty- four children with ADHD performed a Go/ No- Go task during anodal or sham tDCS over the right dlPFC. In the second experiment, twenty- five children with ADHD performed the 1- back working memory task during anodal or sham tDCS over the left dlPFC. We reanalyzed the data after DDM modeling.

RESULTS

The conventional performance measures revealed no significant effect of tDCS on No- Go accuracy in the first experiment and 1-back accuracy in the second experiment. The 1-back reaction time and speed-accuracy tradeoff were however improved under the real stimulation condition. The DDM measures identified increased No-Go- bias and decision time with respect to inhibitory control, and an increased threshold and amount of information required for response in the 1- back test.

CONCLUSION

In children with ADHD, anodal tDCS over the right dlPFC induces more conservative and less impulsive decisions. Furthermore, anodal tDCS over the left dlPFC enhanced efficacy of working memory performance with respect to agility and capacity. The experimental results show that drift diffusion modeling is useful for evaluation of the impact of tDCS on the style of information processing.

Evaluation of Sleep Habits, Generalized Anxiety, Perceived Stress, and Research Outputs Among Postgraduate Research Students in Hong Kong During the Coronavirus (COVID-19) Pandemic

Purpose

The current study aimed to evaluate the impact of coronavirus (COVID-19) pandemic on sleep hygiene, anxiety levels, perceived stress, and research output among postgraduate research students in Hong Kong.

Methods

An online survey was developed and distributed to Hong Kong postgraduate research students. The sleep hygiene, anxiety levels, and perceived stress during the outbreak of COVID-19 were assessed. Questions about COVID-19’s impact on research outputs were asked.

Results

A total of 108 (response rate, 72%) full-time postgraduate students (PhD, 64%; M Phil, 8%; and Masters, 28%) participated. Approximately 83% of students reported poor sleep hygiene. Similarly, nearly 76% of students reported mild to severe levels of self-perceived anxiety levels. Most of the respondents (89%) expressed a moderate level of perceived stress. Sleep hygiene scores were moderately associated with anxiety levels (r = 0.384, p < 0.01) and perceived stress scores (r = 0.423, p < 0.01). Perceived stress was strongly correlated with anxiety levels (r = 0.601, p < 0.01). A hierarchical regression analysis revealed a significant association between respondents’ ethnicity (B = −0.923, p = 0.003), past medical history (such as hypertension, diabetes, and musculoskeletal disorders) (B = 1.112, p = 0.005), or poor sleep hygiene (B = 0.259, p = 0.000) and high levels of perceived stress. Additionally, prior medical history (such as hypertension, diabetes, and musculoskeletal disorders) (B = 1.957, p = 0.001) and poor sleep hygiene (B = 0.312, p = 0.000) were found to be strongly related to anxiety levels among postgraduate research students.

Conclusion

This is the first study that highlights poor sleep hygiene, moderate-to-severe levels of anxiety, and perceived stress during the COVID-19 pandemic in postgraduate research students in Hong Kong. These findings will help educators to prepare strategies to alleviate the stress and psychological problems in postgraduate students.

Prevalence of sleep impairment in patients with tinnitus: a systematic review and single-arm meta-analysis

PURPOSE

This study aimed to comprehensively review the literature and synthesize relevant data to examine the pooled prevalence of poor sleep quality (sleep impairment) and assess overall sleep quality in patients with tinnitus.

METHODS

This meta-analysis systematically searched both English (PubMed, Embase, and Web of Science) and Chinese (Wanfang Data Chinese database, Veep Chinese Database, and Chinese National Knowledge Infrastructure) databases. Data extraction and quality assessment were independently performed by two authors. The pooled prevalence of sleep impairment and poor sleep quality was calculated via a random-effects model. Sub-group and sensitivity analyses were performed to explore the source of heterogeneity.

RESULTS

A total of seven studies were included with a total sample of 3041 tinnitus participants. The pooled prevalence of sleep impairment was 53.5% (95% confidence interval: 40.2-66.8%) and the I2 was 97.8% (Q = 7.90, p = 0.000). There were significant differences in the prevalence of poor sleep quality between males and females (39.1% vs. 44.6%, P = 0.034), between different PSQI cut-off values ≥ 7 and > 5 (53.1% vs. 53.8%, P = 0.000), and between sample sizes > 200 and ≤ 200 (54.0% vs. 52.7%, P = 0.000). In non-Asia area, the prevalence (56.6%, 95% CI: 42.6-70.5%) was lower than that in Asia areas (34.5%, 95% CI: 25.7-43.3%).

CONCLUSION

Sleep impairment is common among patients with tinnitus. Development of interventions for conditions associated with poor sleep quality should be recommended to offer a safe and efficacious solution for this population.

Age differences in diffusion model parameters: a meta-analysis

Older adults typically show slower response times in basic cognitive tasks than younger adults. A diffusion model analysis allows the clarification of why older adults react more slowly by estimating parameters that map distinct cognitive components of decision making. The main components of the diffusion model are the speed of information uptake (drift rate), the degree of conservatism regarding the decision criterion (boundary separation), and the time taken up by non-decisional processes (i.e., encoding and motoric response execution; non-decision time). While the literature shows consistent results regarding higher boundary separation and longer non-decision time for older adults, results are more complex when it comes to age differences in drift rates. We conducted a multi-level meta-analysis to identify possible sources of this variance. As possible moderators, we included task difficulty and task type. We found that age differences in drift rate are moderated both by task type and task difficulty. Older adults were inferior in drift rate in perceptual and memory tasks, but information accumulation was even increased in lexical decision tasks for the older participants. Additionally, in perceptual and lexical decision tasks, older individuals benefitted from high task difficulty. In the memory tasks, task difficulty did not moderate the negative impact of age on drift. The finding of higher boundary separation and longer non-decision time in older than younger adults generalized over task type and task difficulty. The results of our meta-analysis are consistent with recent findings of a more pronounced age-related decline in memory than in vocabulary performance.

Discrimination and Sleep among Asians and Pacific Islanders Adults

STUDY OBJECTIVES

To examine the association between discrimination and sleep duration and difficulty among Asians and Pacific Islanders (APIs) in the United States, and to test nativity and ethnic identity (EI) as effect modifiers.

METHODS

This cross-sectional study of 1,765 adults from the National Epidemiology Study of Alcohol and Related Conditions III, assessed discrimination using the Experiences of Discrimination scale. Discrimimation was classified as low, moderate, and high. Regression models were used to examine self-reported sleep duration and difficulty.

RESULTS

In bivariate analyses, individuals with high discrimination had the shortest sleep and reported sleep difficulty most often. Using linear models adjusted for sociodemographic and health characteristics, moderate and high discrimination were associated with 9 minutes (standard error [SE]: 4.8, p <0.10) and 14.4 minutes (SE: 6.0, p <0.05) less sleep, respectively, relative to low discrimination. Individuals with moderate and high discrimination had higher prevalence of sleep difficulty compared to those with low discrimination (prevalence ratio [PR]: 1.51, 95% confidence interval [CI]: 1.14-1.99 and PR: 1.73, 95% CI: 1.33-2.24, respectively). Interaction effect was observed in sleep difficulty by nativity and EI, but not duration. The association between discrimination and sleep difficulty was stronger among US-born relative to foreign-born participants. Among participants with low EI, moderate and high discrimination were associated with sleep difficulty, whereas among those with high EI, only high discrimination displayed this association.

CONCLUSIONS

Discrimination is associated with sleep duration and difficulty, and varies by nativity and EI. Research is needed to improve sleep among APIs that experience discrimination.[.

New insights into the cognitive effects of sleep deprivation by decomposition of a cognitive throughput task

STUDY OBJECTIVES

A cognitive throughput task known as the Digit Symbol Substitution Test (DSST) (or Symbol Digit Modalities Test) has been used as an assay of general cognitive slowing during sleep deprivation. Here, the effects of total sleep deprivation (TSD) on specific cognitive processes involved in DSST performance, including visual search, spatial memory, paired-associate learning, and motor response, were investigated through targeted task manipulations.

METHODS

A total of 12 DSST variants, designed to manipulate the use of specific cognitive processes, were implemented in two laboratory-based TSD studies with N = 59 and N = 26 subjects, respectively. In each study, the Psychomotor Vigilance Test (PVT) was administered alongside the DSST variants.

RESULTS

TSD reduced cognitive throughput on all DSST variants, with response time distributions exhibiting rightward skewing. All DSST variants showed practice effects, which were however minimized by inclusion of a pause between trials. Importantly, TSD-induced impairment on the DSST variants was not uniform, with a principal component analysis revealing three factors. Diffusion model decomposition of cognitive processes revealed that inter-individual differences during TSD on a two-alternative forced choice DSST variant were different from those on the PVT.

CONCLUSIONS

While reduced cognitive throughput has been interpreted to reflect general cognitive slowing, such TSD-induced impairment appears to reflect cognitive instability, like on the PVT, rather than general slowing. Further, comparisons between task variants revealed not one, but three distinct underlying processes impacted by sleep deprivation. Moreover, the practice effect on the task was found to be independent of the TSD effect and minimized by a task pacing manipulation.

Beyond Difference in Reaction Time: Understanding Neuronal Activity during the Preparatory Period of the Decision Process

Even the simplest perceptual tasks are executed with significant interindividual differences in accuracy and RT. In this work, we used the diffusion decision model and multi-electrode EEG signals to study the impact of neuronal activity during the preparatory period on the following decision process in an attention task. Two groups were defined by fast and slow responses during the performance of control trials. A third, control group performed the same experiment but with instructions defining signal for response execution. We observed that the fast-responding group had a shorter duration of nondecision processes (describing both stimulus encoding and response preparation) preceded by lower power of the frontal upper alpha (10-15 Hz) and central beta (21-26 Hz) activities during the preparatory period. To determine whether these differences were followed by a shortening of the early perceptual or late motor process, we analyzed lateralized readiness potential (LRP). The time from LRP onset until response execution (LRP-RT interval) was similar in all three groups, enabling us to interpret shortening of nondecision time as reflecting faster stimulus encoding.

Precision Inhibitory Stimulation of Individual-Specific Cortical Hubs Disrupts Information Processing in Humans

Noninvasive brain stimulation (NIBS) is a promising treatment for psychiatric and neurologic conditions, but outcomes are variable across treated individuals. In principle, precise targeting of individual-specific features of functional brain networks could improve the efficacy of NIBS interventions. Network theory predicts that the role of a node in a network can be inferred from its connections; as such, we hypothesized that targeting individual-specific "hub" brain areas with NIBS should impact cognition more than nonhub brain areas. Here, we first demonstrate that the spatial positioning of hubs is variable across individuals but reproducible within individuals upon repeated imaging. We then tested our hypothesis in healthy individuals using a prospective, within-subject, double-blind design. Inhibition of a hub with continuous theta burst stimulation disrupted information processing during working-memory more than inhibition of a nonhub area, despite targets being separated by only a few centimeters on the right middle frontal gyrus of each subject. Based upon these findings, we conclude that individual-specific brain network features are functionally relevant and could leveraged as stimulation sites in future NIBS interventions.

Can self-validating neuroenhancement be autonomous?

Consider that an individual improves her capacities by neuroscientific means. It turns out that, besides altering her in the way(s) she intended, the enhancement also changes her personality in significant way(s) she did not foresee. Yet the person endorses her new self because the neuroenhancement she underwent changed her. Can the person's approval of her new personality be autonomous? While questions of autonomy have already gathered a significant amount of attention in philosophical literature on human enhancement, the problem just described-henceforth referred to as the question whether self-validating neuroenhancement can be autonomous-would not appear to have received due consideration. This article takes a step towards remedying the shortage. I start by explicating the main points of departure of its argument. In the subsequent sections of the article, I consider several possible reasons for deeming self-validating neuroenhancement incompatible with autonomy. On the basis of the consideration, I propose that self-validating neuroenhancement can be autonomous.

[Relationship between coping style and insomnia in college students: the mediating effect of rumination]

ObjectiveTo explore the mediating effect of rumination on coping style and insomnia in college students.MethodWe surveyed 767 college students from a university in Sichuan Province using Insomnia Severity Index (ISI), Ruminative Responses Scale (RRS), and Trait Coping Style Questionnaire (TCSQ).ResultsThe prevalence of insomnia was 36.6% in the surveyed college students. Positive coping style was negatively correlated with the total score and scores in each dimension of RRS (r=-0.127~-0.116, P < 0.001), and was negatively correlated with the total score of ISI (r=-0.159, P < 0.001). Negative coping style was positively correlated with the total score and the scores in each dimension of RRS (r=0.298-0.334, P < 0.001), and was positively correlated with the total score of ISI (r=0.264, P < 0.001). The total score and the scores in each dimension of RRS were positively correlated with the total score of ISI (r=0.251-0.281, P < 0.001). Rumination had a partial mediating effect on both positive and negative coping style and insomnia.ConclusionCoping style affects insomnia in college students not only directly but also indirectly through the mediating effect of rumination.

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.

A diffusion-model analysis of timing deficits among children with ADHD

OBJECTIVE

Deficits in the ability to perceive time have been proposed as an etiologic mechanism in the development of the cognitive and behavioral characteristics associated with ADHD. However, previous studies testing the presence of timing deficits have produced idiosyncratic results. This is in large part due to the underutilization of insights from basic timing research, and from the inherent difficulty that arises when a single index of performance (i.e., reaction time [RT] or accuracy) is used to index the health of what is essentially a multiple-component process. The current article utilizes a diffusion model approach to isolate the component processes involved in timing (i.e., internal clock speed, decision-making speed, speed/accuracy trade-off strategies, and nondecision time) using a well-validated timing task.

METHOD

Fifty children with ADHD and 32 non-ADHD controls aged 8-12 completed a temporal bisection procedure.

RESULTS

Diffusion model parameters indicated that both the internal clock and decision-making speeds were slower among children with ADHD. However, the strength of evidence for slowed decision making far outweighed evidence for a slower internal clock.

CONCLUSIONS

Slower evidence accumulation during decision making is domain-general deficit in ADHD. Such slowing is consistent with adaptive-gain theories, which posit that a suboptimal ratio of neural signal-to-noise is characteristic of children with ADHD. (PsycINFO Database Record (c) 2019 APA, all rights reserved).

Disentangling specific inhibitory versus general decision-making processes during sleep deprivation using a Go/NoGo ERP paradigm

This study used a Go/NoGo ERP paradigm in which Go and NoGo stimuli occurred rarely and equally often in an attempt to determine if sleep deprivation has a general effect on decision-making or a more specific effect on inhibition. A Go/NoGo task was administered six times to eleven participants during 36 h of sleep deprivation and once again post recovery sleep. In the Go condition, the participant was asked to respond to the rare stimulus. In the separate NoGo condition, the participant was asked to withhold the response to the rare stimulus. ERPs were recorded to the rare stimuli. The NoGo P3 should be attenuated if sleep loss mainly affects inhibitory processes. Both Go and NoGo P3 should be attenuated if sleep loss affects general detection processes. During sleep loss, accuracy decreased for both tasks. RT also gradually increased for the Go task. Performance during the NoGo task was more complex and was better accounted by a speed-accuracy trade-off. Overall, findings indicate that sleep deprivation did not have specific effects on inhibition. However, the amplitude of the Go P3 occurred as early as 12 h after waking and might reflect an effect of task repetition rather than true sleep deprivation. In contrast, the NoGo P3 amplitude was not significantly reduced until after 24 and 36 h of wakefulness, suggesting a true sleep deprivation effect. Both Go and NoGo P3 post recovery sleep did not return to baseline levels, possibly due to residual sleep inertia.

Psychometric Analysis Of The Sleep Hygiene Index And Correlation With Stress And Anxiety Among Saudi University Students

AIMS

This study aimed to assess the psychometric properties of the Sleep Hygiene Index (SHI) instrument in screening poor sleep hygiene practices among Saudi university students. As a secondary goal, the association of sleep hygiene practices with stress and anxiety scores were assessed.

METHODS

Two-hundred and four healthy college and university students aged 18 to 25 years participated in this cross-sectional questionnaire-based survey. Participants were asked to complete the English version of the SHI instrument, the Perceived Stress Scale (PSS-10), the Generalized Anxiety Disorder (GAD-7) scale, and to provide demographic details.

RESULTS

The average scores for the SHI, the GAD-7, and the PSS-10 were 6.6, 5.3, and 16.2, respectively. The internal consistency of the SHI was adequate (McDonald's Omega 0.76). The corrected item-total correlations for all the items were fair (range, 0.31-0.50). A statistically significant positive correlation/association of the SHI scores with the PSS score, GAD-7, and self-reported poor sleep were obtained in this sample of Saudi university students. Factor analysis favored a 4-factor model of the SHI in the study sample.

CONCLUSION

The SHI scale demonstrated an adequate level of internal consistency as a self-reported instrument in the assessment of sleep hygiene among Saudi university students. In addition, poor sleep hygiene was correlated with stress and anxiety scores.

Sleep Deprivation Selectively Upregulates an Amygdala-Hypothalamic Circuit Involved in Food Reward

Sleep loss is associated with increased obesity risk, as demonstrated by correlations between sleep duration and change in body mass index or body fat percentage. Whereas previous studies linked this weight gain to disturbed endocrine parameters after sleep deprivation or restriction, neuroimaging studies revealed upregulated neural processing of food rewards after sleep loss in reward-processing areas such as the anterior cingulate cortex, ventral striatum, and insula. To address this ongoing debate between hormonal versus hedonic factors underlying sleep-loss-associated weight gain, we rigorously tested the association between sleep deprivation and food cue processing using high-resolution fMRI and assessment of hormones. After taking blood samples from 32 lean, healthy, human male participants, they underwent fMRI while performing a neuroeconomic, value-based decision-making task with snack food and trinket rewards following a full night of habitual sleep and a night of sleep deprivation in a repeated-measures crossover design. We found that des-acyl ghrelin concentrations were increased after sleep deprivation compared with habitual sleep. Despite similar hunger ratings due to fasting in both conditions, participants were willing to spend more money on food items only after sleep deprivation. Furthermore, fMRI data paralleled this behavioral finding, revealing a food-reward-specific upregulation of hypothalamic valuation signals and amygdala-hypothalamic coupling after a single night of sleep deprivation. Behavioral and fMRI results were not significantly correlated with changes in acyl, des-acyl, or total ghrelin concentrations. Our results suggest that increased food valuation after sleep loss might be due to hedonic rather than hormonal mechanisms.SIGNIFICANCE STATEMENT Epidemiological studies suggest an association between overweight and reduced nocturnal sleep, but the relative contributions of hedonic and hormonal factors to overeating after sleep loss are a matter of ongoing controversy. Here, we tested the association between sleep deprivation and food cue processing in a repeated-measures crossover design using fMRI. We found that willingness to pay increased for food items only after sleep deprivation. fMRI data paralleled this behavioral finding, revealing a food-reward-specific upregulation of hypothalamic valuation signals and amygdala-hypothalamic coupling after a single night of sleep deprivation. However, there was no evidence for hormonal modulations of behavioral or fMRI findings. Our results suggest that increased food valuation after sleep loss is due to hedonic rather than hormonal mechanisms.

Computational cognitive modeling of the temporal dynamics of fatigue from sleep loss

Computational models have become common tools in psychology. They provide quantitative instantiations of theories that seek to explain the functioning of the human mind. In this paper, we focus on identifying deep theoretical similarities between two very different models. Both models are concerned with how fatigue from sleep loss impacts cognitive processing. The first is based on the diffusion model and posits that fatigue decreases the drift rate of the diffusion process. The second is based on the Adaptive Control of Thought - Rational (ACT-R) cognitive architecture and posits that fatigue decreases the utility of candidate actions leading to microlapses in cognitive processing. A biomathematical model of fatigue is used to control drift rate in the first account and utility in the second. We investigated the predicted response time distributions of these two integrated computational cognitive models for performance on a psychomotor vigilance test under conditions of total sleep deprivation, simulated shift work, and sustained sleep restriction. The models generated equivalent predictions of response time distributions with excellent goodness-of-fit to the human data. More importantly, although the accounts involve different modeling approaches and levels of abstraction, they represent the effects of fatigue in a functionally equivalent way: in both, fatigue decreases the signal-to-noise ratio in decision processes and decreases response inhibition. This convergence suggests that sleep loss impairs psychomotor vigilance performance through degradation of the quality of cognitive processing, which provides a foundation for systematic investigation of the effects of sleep loss on other aspects of cognition. Our findings illustrate the value of treating different modeling formalisms as vehicles for discovery.

The effects of sleep deprivation on item and associative recognition memory

Sleep deprivation adversely affects the ability to perform cognitive tasks, but theories range from predicting an overall decline in cognitive functioning because of reduced stability in attentional networks to specific deficits in various cognitive domains or processes. We measured the effects of sleep deprivation on two memory tasks, item recognition ("was this word in the list studied") and associative recognition ("were these two words studied in the same pair"). These tasks test memory for information encoded a few minutes earlier and so do not address effects of sleep deprivation on working memory or consolidation after sleep. A diffusion model was used to decompose accuracy and response time distributions to produce parameter estimates of components of cognitive processing. The model assumes that over time, noisy evidence from the task stimulus is accumulated to one of two decision criteria, and parameters governing this process are extracted and interpreted in terms of distinct cognitive processes. Results showed that sleep deprivation reduces drift rate (evidence used in the decision process), with little effect on the other components of the decision process. These results contrast with the effects of aging, which show little decline in item recognition but large declines in associative recognition. The results suggest that sleep deprivation degrades the quality of information stored in memory and that this may occur through degraded attentional processes. (PsycINFO Database Record

Testing the validity of conflict drift-diffusion models for use in estimating cognitive processes: A parameter-recovery study

Researchers and clinicians are interested in estimating individual differences in the ability to process conflicting information. Conflict processing is typically assessed by comparing behavioral measures like RTs or error rates from conflict tasks. However, these measures are hard to interpret because they can be influenced by additional processes like response caution or bias. This limitation can be circumvented by employing cognitive models to decompose behavioral data into components of underlying decision processes, providing better specificity for investigating individual differences. A new class of drift-diffusion models has been developed for conflict tasks, presenting a potential tool to improve analysis of individual differences in conflict processing. However, measures from these models have not been validated for use in experiments with limited data collection. The present study assessed the validity of these models with a parameter-recovery study to determine whether and under what circumstances the models provide valid measures of cognitive processing. Three models were tested: the dual-stage two-phase model (Hübner, Steinhauser, & Lehle, Psychological Review, 117(3), 759-784, 2010), the shrinking spotlight model (White, Ratcliff, & Starns, Cognitive Psychology, 63(4), 210-238, 2011), and the diffusion model for conflict tasks (Ulrich, Schröter, Leuthold, & Birngruber, Cogntive Psychology, 78, 148-174, 2015). The validity of the model parameters was assessed using different methods of fitting the data and different numbers of trials. The results show that each model has limitations in recovering valid parameters, but they can be mitigated by adding constraints to the model. Practical recommendations are provided for when and how each model can be used to analyze data and provide measures of processing in conflict tasks.

How many trials are required for parameter estimation in diffusion modeling? A comparison of different optimization criteria

Diffusion models (Ratcliff, 1978) make it possible to identify and separate different cognitive processes underlying responses in binary decision tasks (e.g., the speed of information accumulation vs. the degree of response conservatism). This becomes possible because of the high degree of information utilization involved. Not only mean response times or error rates are used for the parameter estimation, but also the response time distributions of both correct and error responses. In a series of simulation studies, the efficiency and robustness of parameter recovery were compared for models differing in complexity (i.e., in numbers of free parameters) and trial numbers (ranging from 24 to 5,000) using three different optimization criteria (maximum likelihood, Kolmogorov-Smirnov, and chi-square) that are all implemented in the latest version of fast-dm (Voss, Voss, & Lerche, 2015). The results revealed that maximum likelihood is superior for uncontaminated data, but in the presence of fast contaminants, Kolmogorov-Smirnov outperforms the other two methods. For most conditions, chi-square-based parameter estimations lead to less precise results than the other optimization criteria. The performance of the fast-dm methods was compared to the EZ approach (Wagenmakers, van der Maas, & Grasman, 2007) and to a Bayesian implementation (Wiecki, Sofer, & Frank, 2013). Recommendations for trial numbers are derived from the results for models of different complexities. Interestingly, under certain conditions even small numbers of trials (N < 100) are sufficient for robust parameter estimation.

Thou Shalt Not Bear False Witness Against Null Hypothesis Significance Testing

Null hypothesis significance testing (NHST) has been the subject of debate for decades and alternative approaches to data analysis have been proposed. This article addresses this debate from the perspective of scientific inquiry and inference. Inference is an inverse problem and application of statistical methods cannot reveal whether effects exist or whether they are empirically meaningful. Hence, raising conclusions from the outcomes of statistical analyses is subject to limitations. NHST has been criticized for its misuse and the misconstruction of its outcomes, also stressing its inability to meet expectations that it was never designed to fulfil. Ironically, alternatives to NHST are identical in these respects, something that has been overlooked in their presentation. Three of those alternatives are discussed here (estimation via confidence intervals and effect sizes, quantification of evidence via Bayes factors, and mere reporting of descriptive statistics). None of them offers a solution to the problems that NHST is purported to have, all of them are susceptible to misuse and misinterpretation, and some bring around their own problems (e.g., Bayes factors have a one-to-one correspondence with p values, but they are entirely deprived of an inferential framework). Those alternatives also fail to cover a broad area of inference not involving distributional parameters, where NHST procedures remain the only (and suitable) option. Like knives or axes, NHST is not inherently evil; only misuse and misinterpretation of its outcomes needs to be eradicated.

Whole dietary patterns to optimize cognitive function for military mission-readiness: a systematic review and recommendations for the field

Context

Optimizing cognitive performance, particularly during times of high stress, is a prerequisite to mission-readiness among military personnel. It has been of interest to determine whether such performance could be enhanced through diet.

Objective

This systematic review assesses the quality of the evidence for whole dietary patterns across various outcomes related to cognitive function in healthy adult populations to develop research recommendations for the military.

Data Sources

PubMed, CINAHL, Embase, PsycInfo, and the Cochrane Library were searched.

Study Selection

Peer-reviewed randomized controlled trials published in the English language were eligible.

Data Extraction

Fifteen included trials were assessed for methodological quality, and descriptive data were extracted.

Data Synthesis

Of the 6 acceptable-quality studies, 1 demonstrated statistically nonsignificant results, whereas the other 5 showed conflicting results across the cognitive outcomes assessed.

Conclusions

Due to the heterogeneity across the included studies, no recommendations could be reached concerning whether certain whole dietary patterns have an effect on cognitive outcomes in healthy populations. Specific recommendations for future research are offered.

The prevalence and association of stress with sleep quality among medical students

Introduction: Medical students tend to reduce their sleep, in an effort to adjust and cope with their workload and stressful environment. This study estimated the prevalence of and the relationship between poor sleep quality and stress among medical students.

Methods: This cross-sectional study was conducted using a stratified random sample of male and female medical students in King Saud bin Abdulaziz University for Health Sciences in Riyadh, Saudi Arabia. A self-administered questionnaire was distributed to assess sleep quality using the Pittsburgh Sleep Quality Index, and the stress level by using the Kessler Psychological Distress Scale.

Results: A high prevalence of poor sleep quality (76%) and stress (53%) were found, with a statistically significant association (p < 0.001). Logistic regression indicated that students who are not suffering from stress are less likely to have poor sleep quality (OR = 0.28, p < 0.001), and the risk of having poor sleep quality is almost four times higher in students whose cumulative grade point average (GPA) is less than 4.25 (OR = 3.83, p = 0.01).

Conclusion: The study documents a statistically significant association between stress and poor sleep quality. A recommendation for the management of medical college is to establish academic counseling centers focusing in promoting good sleep hygiene and strengthening students’ study skills and coping with their stressful environment.

The EZ diffusion model provides a powerful test of simple empirical effects

Over the last four decades, sequential accumulation models for choice response times have spread through cognitive psychology like wildfire. The most popular style of accumulator model is the diffusion model (Ratcliff Psychological Review, 85, 59-108, 1978), which has been shown to account for data from a wide range of paradigms, including perceptual discrimination, letter identification, lexical decision, recognition memory, and signal detection. Since its original inception, the model has become increasingly complex in order to account for subtle, but reliable, data patterns. The additional complexity of the diffusion model renders it a tool that is only for experts. In response, Wagenmakers et al. (Psychonomic Bulletin & Review, 14, 3-22, 2007) proposed that researchers could use a more basic version of the diffusion model, the EZ diffusion. Here, we simulate experimental effects on data generated from the full diffusion model and compare the power of the full diffusion model and EZ diffusion to detect those effects. We show that the EZ diffusion model, by virtue of its relative simplicity, will be sometimes better able to detect experimental effects than the data-generating full diffusion model.

Sleep disturbances in caregivers of patients with advanced cancer: A systematic review

OBJECTIVE

Sleep disturbances are a common issue for those who provide informal care to someone with a life-limiting condition. The negative consequences of poor sleep are well documented. The purpose of the present study was to determine the sleep patterns of caregivers of patients with advanced cancer.

METHOD

An extensive systematic review of studies reporting empirical sleep data was undertaken in 2015 in accordance with the PRISMA Statement. A total of eight electronic databases were searched, with no date restrictions imposed. Additionally, a search of the bibliographies of the studies identified during the electronic search was conducted. Search terms included: "sleep," "insomnia," "sleep disturbance," "circadian rhythm," "caregiver," "carer," "advanced cancer," "palliative cancer," and MESH suggestions. The inclusion criteria required studies to be in English and to report primary qualitative and/or quantitative research that examined sleep in caregivers of patients with advanced cancer. Unpublished studies, conference papers, and dissertations were excluded.

RESULTS

Overall, 10 studies met the inclusion criteria and were included in the review. Two major findings emerged from the data synthesis. First, at least 72% of caregivers reported moderate to severe sleep disturbance as measured by the Pittsburgh Sleep Quality Index. Second, objective measurement of caregivers' sleep identified that some caregivers experienced up to a 44% reduction in their total sleep time compared to the recommended eight hours.

SIGNIFICANCE OF RESULTS

Reduction in total sleep time appears to be the biggest issue facing caregivers' sleep. Future studies need to explore the specific factors that cause these sleep disturbances and thus help to identify interventions to optimize sleep.

Modeling Individual Differences in the Go/No-go Task with a Diffusion Model

The go/no-go task is one in which there are two choices, but the subject responds only to one of them, waiting out a time-out for the other choice. The task has a long history in psychology and modern applications in the clinical/neuropsychological domain. In this article we fit a diffusion model to both experimental and simulated data. The model is the same as the two-choice model and assumes that there are two decision boundaries and termination at one of them produces a response and at the other, the subject waits out the trial. In prior modeling, both two-choice and go/no-go data were fit simultaneously and only group data were fit. Here the model is fit to just go/no-go data for individual subjects. This allows analyses of individual differences which is important for clinical applications. First, we fit the standard two-choice model to two-choice data and fit the go/no-go model to RTs from one of the choices and accuracy from the two-choice data. Parameter values were similar between the models and had high correlations. The go/no-go model was also fit to data from a go/no-go version of the task with the same subjects as the two-choice task. A simulation study with ranges of parameter values that are obtained in practice showed similar parameter recovery between the two-choice and go/no-go models. Results show that a diffusion model with an implicit (no response) boundary can be fit to data with almost the same accuracy as fitting the two-choice model to two-choice data.

Comparing fixed and collapsing boundary versions of the diffusion model

Optimality studies and studies of decision-making in monkeys have been used to support a model in which the decision boundaries used to evaluate evidence collapse over time. This article investigates whether a diffusion model with collapsing boundaries provides a better account of human data than a model with fixed boundaries. We compared the models using data from four new numerosity discrimination experiments and two previously published motion discrimination experiments. When model selection was based on BIC values, the fixed boundary model was preferred over the collapsing boundary model for all of the experiments. When model selection was carried out using a parametric bootstrap cross-fitting method (PBCM), which takes into account the flexibility of the alternative models and the ability of one model to account for data from another model, data from 5 of 6 experiments favored either fixed boundaries or boundaries with only negligible collapse. We found that the collapsing boundary model produces response times distributions with the same shape as those produced by the fixed boundary model and that its parameters were not well-identified and were difficult to recover from data. Furthermore, the estimated boundaries of the best-fitting collapsing boundary model were relatively flat and very similar to those of the fixed-boundary model. Overall, a diffusion model with decision boundaries that converge over time does not provide an improvement over the standard diffusion model for our tasks with human data.

Daytime Sleepiness Is Associated With Reduced Integration of Temporally Distant Outcomes on the Iowa Gambling Task

Sleep deprivation is associated with performance decrements on some measures of executive functioning. For instance, sleep deprivation results in altered decision making on the Iowa Gambling Task. However, it is unclear which component processes of the task may be driving the effect. In this study, Iowa Gambling task performance was decomposed using the Expectancy-Valence model. Recent sleep debt and greater daytime sleepiness were associated with higher scores on the updating parameter, which reflects the extent to which recent experiences are emphasized over remote ones. Findings suggest that the effects of insufficient sleep on IGT performance are due to shortening of the time horizon over which decisions are integrated. These findings may have clinical implications in that individuals with sleep problems may not integrate more temporally distant information when making decisions.

Sleep-deprived motor vehicle operators are unfit to drive: a multidisciplinary expert consensus statement on drowsy driving

OBJECTIVES

This article presents the consensus findings of the National Sleep Foundation Drowsy Driving Consensus Working Group, which was an expert panel assembled to establish a consensus statement regarding sleep-related driving impairment.

METHODS

The National Sleep Foundation assembled a expert panel comprised of experts from the sleep community and experts appointed by stakeholder organizations. A systematic literature review identified 346 studies that were abstracted and provided to the panelists for review. A modified Delphi RAND/UCLA Appropriateness Method with 2 rounds of voting was used to reach consensus.

RESULTS

A final consensus was reached that sleep deprivation renders motorists unfit to drive a motor vehicle. After reviewing growing evidence of impairment and increased crash risk among drivers who obtained less than optimal sleep duration in the preceding 24 hours, the panelists recognized the need for public policy guidance as to when it is certainly unsafe to drive. Toward this end, the panelists agreed upon the following expert consensus statement: "Drivers who have slept for two hours or less in the preceding 24 hours are not fit to operate a motor vehicle." Panelists further agreed that most healthy drivers would likely be impaired with only 3 to 5 hours of sleep during the prior 24 hours.

CONCLUSIONS

There is consensus among experts that healthy individuals who have slept for 2 hours or less in the preceding 24 hours are too impaired to safely operate a motor vehicle. Prevention of drowsy driving will require sustained and collaborative effort from multiple stakeholders. Implications and limitations of the consensus recommendations are discussed.

Relationship Between Short Sleep Duration and Preseason Concussion Testing

OBJECTIVE

Baseline, preseason assessment of cognition, symptoms, and balance has been recommended as part of a comprehensive sport concussion management program. We examined the relationship between sleep and baseline test results. We hypothesized that adolescents who slept fewer hours the night before would report more symptoms and perform more poorly on cognitive testing than students who had a full night sleep.

DESIGN

Cross-sectional observation study.

SETTING

Preseason concussion testing for high school athletes.

PARTICIPANTS

A large sample (n = 2928) of student athletes from Maine, USA, between the ages of 13 and 18 years completed preseason testing. Participants with developmental problems, a history of treatment for neurological or psychiatric problems, recent concussion, or 3 or more prior concussions were excluded.

ASSESSMENT OF RISK FACTORS

Athletes were divided into 4 groups based on their sleep duration the night before testing.

MAIN OUTCOME MEASURES

Immediate Post-Concussion Assessment and Cognitive Testing (ImPACT; ImPACT Applications, Inc, Pittsburgh, PA) cognitive composite scores and the embedded Post-Concussion Symptom Scale.

RESULTS

Sleep was not related to any ImPACT cognitive composite score, after covarying for age and controlling for multiple comparisons. In contrast, there were sleep duration, sex, and sleep duration by sex effects on the Post-Concussion Symptom Scale. The effect of sleep duration on symptom reporting was more pronounced in girls. Supplementary analyses suggested that sleep insufficiency was associated with a diverse array of postconcussion-like symptoms.

CONCLUSIONS

Poor sleep the night before baseline or postinjury testing may be an important confound when assessing postconcussion symptoms. Girls may be more vulnerable to experiencing and reporting symptoms following insufficient sleep.

CLINICAL RELEVANCE

Clinicians should routinely ask how the athlete slept the night before preseason baseline testing and consider deferring the symptom assessment or later retesting athletes who slept poorly.

Diffusion Decision Model: Current Issues and History

There is growing interest in diffusion models to represent the cognitive and neural processes of speeded decision making. Sequential-sampling models like the diffusion model have a long history in psychology. They view decision making as a process of noisy accumulation of evidence from a stimulus. The standard model assumes that evidence accumulates at a constant rate during the second or two it takes to make a decision. This process can be linked to the behaviors of populations of neurons and to theories of optimality. Diffusion models have been used successfully in a range of cognitive tasks and as psychometric tools in clinical research to examine individual differences. In this review, we relate the models to both earlier and more recent research in psychology.