Generally, microsleeps are characterized by a decrease in activity in wakefulness-related regions of the brain and an increase in activity in sleep-related regions of the brain. Looking at neural correlates of microsleeps is difficult because microsleeps can also be triggered by monotonous tasks (e.g. such as driving or dozing off in class). Therefore, it is important to examine neural correlates of microsleep events with respect to experimental set-ups (e.g.
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The AMI published findings that "total sleep time was substantially reduced as compared to the usual 7–8 hour monophasic nocturnal sleep" while "maintaining good levels of vigilance as shown by the virtual absence of EEG microsleeps." EEG microsleeps are measurable and usually unnoticeable bursts of sleep in the brain while a subject appears to be awake. Nocturnal sleepers who sleep poorly may be heavily bombarded with microsleeps during waking hours, limiting focus and attention.
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Microsleeps occur when a person has a significant sleep deprivation. Microsleeps usually last for a few seconds and happen most frequently when a person is trying to stay awake when they are feeling sleepy. The person usually falls into microsleep while doing a monotonous task like driving, reading a book, or staring at a computer. Microsleeps are similar to blackouts and a person experiencing them is not consciously aware that they are occurring.
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They are considered microsleeps if they last less than thirty seconds. Microsleep cases for pilots on outgoing flights were half compared to the number on incoming flights back to the home base showing that fatigue is more prevalent on flights returning home. Pilots are more prone to microsleeps during the cruise phase of the flight while they are more alert and less likely to experience microsleeps during the take-off, approach and landing phases of the flight. Findings also show that fatigue was greater during night flights because pilots had already been awake for more than 12 hours and would begin duty by the time they were due to go to sleep.
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The second questionnaire also administered during flight, assessed different dimensions including mental, physical and temporal demand as well as performance. Key findings from the study conveyed that: outgoing flights from the home base were rated as less stressful and night flights were rated as the most stressful. The physiological measures found that microsleeps recorded by the EEGs increased progressively with flight duty. Microsleeps are recordings of alpha wave activity and they occur during wakeful relaxation often resulting in loss of attention.
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Therefore, the study concluded that decision-making was not activated immediately upon waking up from a MS episode, likely increasing risk of injury in intense decision-making tasks like driving or surgery. The transition from wakefulness to sleep is regulated by a variety of chemicals. Adenosine likely causes the 'feeling sleepy' side of microsleeps, while dopamine likely reduces microsleep events by promoting wakefulness. It has been shown that microsleeps correlate with spontaneous pontine-geniculate-occipital (PGO waves) waves, which suppress visual processing in the basal ganglia.
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Microsleep is extremely dangerous when they occur in situations that demand constant alertness, such as driving a motor vehicle or working with heavy machinery. People who experience microsleeps often remain unaware of them, instead believing themselves to have been awake the whole time, or to have temporarily lost focus.
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Participants performed this task in an fMRI scanner such that joystick response, right eye-video, EEG (60 EEG electrodes), and fMRI data were recorded simultaneously. Most participants had frequent microsleeps (>35) in a continuous visuomotor task (tracking visual stimulus on a screen), corresponding with decreased activity in arousal-related brain regions over time (thalamus, midbrain, and the posterior cingulate cortex). Another study examined the activation patterns of 5 people who woke up from microsleeps in a simulated driving experiment. It was found that upon awakening the visual area, frontal cortex, limbic lobe were activated (in the intense activation phase) and the frontal cortex, temporal cortex, primary motor area, and insula were activated (in the post abrupt awakening phase).
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Few studies have compared the effects of acute total sleep deprivation and chronic partial sleep restriction. Complete absence of sleep over long periods is not frequent in humans (unless they suffer from fatal familial insomnia or specific issues caused by surgery); it appears that brief microsleeps cannot be avoided. Long- term total sleep deprivation has caused death in lab animals.
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According to news reports, Gardner's record has been broken a number of times. Some of these cases are described below for comparison. Gardner's case still stands out, however, because it has been so extensively documented. It is difficult to determine the accuracy of a sleep deprivation period unless the participant is carefully observed to detect short microsleeps, which the participant might not even notice.
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An fMRI study of abrupt-awake episodes during behavioral microsleeps. In Engineering in Medicine and Biology Society, EMBC, 2011 Annual International Conference of the IEEE (pp. 5060-5063). IEEE. Some experts define microsleep according to behavioral criteria (head nods, drooping eyelids, etc.), while others rely on EEG markers. Since there are many ways to detect MSs in a variety of contexts there is little agreement on how best to identify and classify microsleep episodes.
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Somnolence is often viewed as a symptom rather than a disorder by itself. However, the concept of somnolence recurring at certain times for certain reasons constitutes various disorders, such as excessive daytime sleepiness, shift work sleep disorder, and others; and there are medical codes for somnolence as viewed as a disorder. Sleepiness can be dangerous when performing tasks that require constant concentration, such as driving a vehicle. When a person is sufficiently fatigued, microsleeps may be experienced.
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In behavioral terms, MSs manifest as droopy eyes, slow eyelid- closure, and head nodding. In electrical terms, microsleeps are often classified as a shift in electroencephalography (EEG) during which 4–7 Hz (theta wave) activity replaces the waking 8–13 Hz (alpha wave) background rhythm. MSs often occur as a result of sleep deprivation, though normal non- sleep deprived individuals can also experience MSs during monotonous tasks.Chou, Y. H., Chuang, C. C., Zao, J. K., Ko, L. W., & Lin, C. T. (2011, August).
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The duration of a blink is on average 100–150 milliseconds according to UCL researcher and between 100–400 ms according to the Harvard Database of Useful Biological Numbers. Closures in excess of 1000 ms were defined as microsleeps. Greater activation of dopaminergic pathways dopamine production in the striatum is associated with a higher rate of spontaneous eye blinking. Conditions in which there is reduced dopamine availability such as Parkinson's disease have reduced eye blink rate, while conditions in which it is raised such as schizophrenia have an increased rate.
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Refusing to believe her mother's story, Nancy attempts to track down the remaining kids from the school but discovered that all of them have been killed, most of them in their sleep, and after Jesse's death, only she and Quentin are left. Meanwhile, Quentin falls asleep during his swim practice and witness Krueger's fate after the parents led by Alan tracked him down and burned him alive. As a result of their insomnia, they have sporadic microsleeps and become hypnagogic. To try to stop Krueger, they decide to go to the preschool to learn what they can.
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To empirically measure the magnitude of attention deficits, researchers typically employ the psychomotor vigilance task (PVT) which requires the subject to press a button in response to a light at random intervals. Failure to press the button in response to the stimulus (light) is recorded as an error, attributable to the microsleeps that occur as a product of sleep deprivation. Crucially, individuals' subjective evaluations of their fatigue often do not predict actual performance on the PVT. While totally sleep-deprived individuals are usually aware of the degree of their impairment, lapses from chronic (lesser) sleep deprivation can build up over time so that they are equal in number and severity to the lapses occurring from total (acute) sleep deprivation.
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Example of an EEG alpha wave Example of an EEG theta wave A microsleep (MS) is a temporary episode of sleep or drowsiness which may last for a fraction of a second or up to 30 seconds where an individual fails to respond to some arbitrary sensory input and becomes unconscious. International Classification of Sleep Disorders Diagnostic and Coding Manual, , page 343Poudel, G. R., Innes, C. R., Bones, P. J., Watts, R., & Jones, R. D. (2012). Losing the struggle to stay awake: Divergent thalamic and cortical activity during microsleeps. Human Brain Mapping: 00:000-000 MSs occur when an individual loses awareness and subsequently gains awareness after a brief lapse in consciousness, or when there are sudden shifts between states of wakefulness and sleep.
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