The effects of 28 h of sleep deprivation were compared with varying doses of alcohol up to 0.1% blood alcohol concentration (BAC) in the same subjects. The study was conducted in the laboratory. Twenty long-haul truck drivers and 19 people not employed as professional drivers acted as subjects. Tests were selected that were likely to be affected by fatigue, including simple reaction time, unstable tracking, dual task, Mackworth clock vigilance test, symbol digit coding, visual search, sequential spatial memory and logical reasoning. While performance effects were seen due to alcohol for all tests, sleep deprivation affected performance on most tests, but had no effect on performance on the visual search and logical reasoning tests. Some tests showed evidence of a circadian rhythm effect on performance, in particular, simple reaction time, dual task, Mackworth clock vigilance, and symbol digit coding, but only for response speed and not response accuracy. Drivers were slower but more accurate than controls on the symbol digit test, suggesting that they took a more conservative approach to performance of this test. This study demonstrated which tests are most sensitive to sleep deprivation and fatigue. The study therefore has established a set of tests that can be used in evaluations of fatigue and fatigue countermeasures.
"It has been shown that sleep-dependent motor skill memory improvement was dependent on the nature of the skill to be learned (Cohen et al., 2005; Cohen and Robertson, 2007; Siengsukon and Boyd, 2008). In another study, perception, attention and memory were impaired by sleep deprivation, but visual search and logical reasoning tasks were not (Williamson et al., 2001). A deficit in perceptual classification ability in an information-integration task was observed for some, but not all, sleep-deprived individuals (Maddox et al., 2009). "
[Show abstract][Hide abstract] ABSTRACT: Inability to solve complex problems or errors in decision making is often attributed to poor brain processing, and raises the issue of brain augmentation. Investigation of neuronal activity in the cerebral cortex in the sleep-wake cycle offers insights into the mechanisms underlying the reduction in mental abilities for complex problem solving. Some cortical areas may transit into a sleep state while an organism is still awake. Such local sleep would reduce behavioral ability in the tasks for which the sleeping areas are crucial. The studies of this phenomenon have indicated that local sleep develops in high order cortical areas. This is why complex problem solving is mostly affected by local sleep, and prevention of local sleep might be a potential way of augmentation of brain function. For this approach to brain augmentation not to entail negative consequences for the organism, it is necessary to understand the functional role of sleep. Our studies have given an unexpected answer to this question. It was shown that cortical areas that process signals from extero- and proprioreceptors during wakefulness, switch to the processing of interoceptive information during sleep. It became clear that during sleep all "computational power" of the brain is directed to the restoration of the vital functions of internal organs. These results explain the logic behind the initiation of total and local sleep. Indeed, a mismatch between the current parameters of any visceral system and the genetically determined normal range would provide the feeling of tiredness, or sleep pressure. If an environmental situation allows falling asleep, the organism would transit to a normal total sleep in all cortical areas. However, if it is impossible to go to sleep immediately, partial sleep may develop in some cortical areas in the still behaviorally awake organism. This local sleep may reduce both the "intellectual power" and the restorative function of sleep for visceral organs.
Frontiers in Systems Neuroscience 05/2014; 8:75. DOI:10.3389/fnsys.2014.00075
"Comparison of performance deterioration due to sleepiness with performance deterioration caused by measured concentrations of alcohol consumption is one means of determining whether a particular level of sleepiness is likely to increase accident risk. This method has been utilized to determine that performance on a variety of tasks after 24 h awake is similar to performance at a BAC of 0.08–0.10% in a non-sleepdeprived state (Dawson and Reid, 1997; Lamond and Dawson, 1999; Williamson et al., 2001). This study evaluated specific symptoms as markers of sleepiness and performance impairment. "
[Show abstract][Hide abstract] ABSTRACT: Drivers are not always aware that they are becoming impaired as a result of sleepiness. Using specific symptoms of sleepiness might assist with recognition of drowsiness related impairment and help drivers judge whether they are safe to drive a vehicle, however this has not been evaluated. In this study, 20 healthy volunteer professional drivers completed two randomized sessions in the laboratory - one under 24h of acute sleep deprivation, and one with alcohol. The Psychomotor Vigilance Task (PVT) and a 30min simulated driving task (AusEdTM) were performed every 3-4h in the sleep deprivation session, and at a BAC of 0.00% and 0.05% in the alcohol session, while electroencephalography (EEG) and eye movements were recorded. After each test session, drivers completed the Karolinska Sleepiness Scale (KSS) and the Sleepiness Symptoms Questionnaire (SSQ), which includes eight specific sleepiness and driving performance symptoms. A second baseline session was completed on a separate day by the professional drivers and in an additional 20 non-professional drivers for test-retest reliability. There was moderate test-retest agreement on the SSQ (r=0.59). Significant correlations were identified between individual sleepiness symptoms and the KSS score (r values 0.50-0.74, p<0.01 for all symptoms). The frequency of all SSQ items increased during sleep deprivation (χ(2) values of 28.4-80.2, p<0.01 for all symptoms) and symptoms were related to increased subjective sleepiness and performance deterioration. The symptoms "struggling to keep your eyes open", "difficulty maintaining correct speed", "reactions were slow" and "head dropping down" were most closely related to increased alpha and theta activity on EEG (r values 0.49-0.59, p<0.001) and "nodding off to sleep" and "struggling to keep your eyes open" were related to slow eye movements (r values 0.67 and 0.64, p<0.001). Symptoms related to visual disturbance and impaired driving performance were most accurate at detecting severely impaired driving performance (AUC on ROC curve of 0.86-0.91 for detecting change in lateral lane position greater than the change at a BAC of 0.05%). Individual sleepiness symptoms are related to impairment during acute sleep deprivation and might be able to assist drivers in recognizing their own sleepiness and ability to drive safely.
"Since then tests based on the principle of this first vigilance test designed by Mackworth have been called Mackworth clock tests [17– 19]. The Mackworth clock test was further developed and adapted for personal computers in various versions during the last decades and has been applied in several studies on vigilance in healthy participants    , in studies on pharmacological effects   , and on the effects of sleep deprivation on vigilance   . In a number of clinical trials using this kind of vigilance task, patients with severe sleep apnea syndrome demonstrated impaired performance compared to healthy controls  . "
[Show abstract][Hide abstract] ABSTRACT: Objective:
In several modern society duties individuals have to maintain their attention or vigilance over prolonged periods of time, even if the monitoring task is monotonous. The aim of our study was to obtain reference data on the 60-minute monotonous Siesta sustained attention test.
Normative data were gathered in an age-stratified sample of 234 healthy participants (118 men; 116 women) between the ages of 20 and 79 years. The impact of age, gender, time of day, and time on task during performance was analyzed.
At least 20 participants from each age group and gender group were tested either in the morning or in the afternoon. The sample sizes were only smaller in the age group of 70 to 79 years. There was a notable age effect on all performance measures, with an increase in reaction times and false response rates from the youngest to the oldest group as well as a decrease in correct reactions with increasing age. Statistical analysis revealed no differences in speed and accuracy measures between men and women participants. There was no notable time-of-day effect but a clear impact of time-on-task speed and of correct reactions during the course of the test. The vigilance decrement had already occurred during the first half of the test.
Our results provide a normative database of performance parameters for different age groups in healthy adult participants. As sustained attention is sensitive to sleep loss and nonrestorative sleep, our data can be used as a reference for performance-based assessment of daytime sleepiness in participants with hypersomnia.
Sleep Medicine 03/2013; 14(6). DOI:10.1016/j.sleep.2013.01.011 · 3.15 Impact Factor
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