Microsleep

Microsleep is an episode of sleep lasting from a fraction of a second to several seconds. They are fleeting, uncontrollable episodes of sleep occurring when one is awake.  It often occurs as a result of sleep deprivation, or mental fatigue, sleep apnea, narcolepsy, or hypersomnia. People who experience excessive daytime sleepiness are at high risk for microsleep episodes.  Although they may last only a few seconds, microsleeps can cause major automobile accidents, machinery-related accidents, and other dangerous conditions.

Microsleeps can occur at any time, typically without significant warning. In the middle of even lively conversations, the onset of a microsleep episode can cause sufferers to 'suddenly' lose sync in a conversation.

Microsleeps (or microsleep episodes) become extremely dangerous when occurring during situations which demand continual alertness, such as driving a motor vehicle or working with heavy machinery. People who experience microsleeps usually remain unaware of them, instead they strongly believe to have been awake the whole time, or feeling a sensation of 'spacing out'. One example is called "gap driving": from the perspective of the driver, he or she was driving a car, and then suddenly realizes that several seconds have passed by unnoticed. It is not obvious to the driver that he was asleep during those missing seconds, although this is in fact what happened. The sleeping driver is at very high risk for having an accident during a microsleep episode. Many accidents and catastrophes have resulted from microsleep episodes in these circumstances. For example, a microsleep episode is believed to have been one factor contributing to the Waterfall train disaster in 2003.

Many people experience microsleep episodes during sleep deprivation, in which they sleep for periods of seconds to fractions of a second and frequently don't remember these episodes. Because microsleep is frequently not remembered, microsleep or a related phenomenon may be responsible for lack of sleep and/or lack of memory of sleep in individuals like Nesterchuk and Thai Ngoc.

Microsleeps are often the cause of short term memory deficits, increased reaction times, and generally poorer task performance associated with sleep deprivation, since presented stimuli may not actually be registered by the subject during a microsleep. The same mechanism can also explain some longer term effects on memory (but it is not the only agent).

A method and apparatus for determining, monitoring and predicting levels of alertness by detecting microsleep episodes includes a plurality of channel processing units and a channel combining unit.

Each of the channel processing units receives an information channel which conveys information associated with the mental state of the subject, such as an EEG channel, and classifies the information into a distinct category. Such categories may include microsleep, non-microsleep, one or more of a plurality of stages of sleep, one or more of a plurality of stages of wakefulness, or a transition state characterized by a transition from one of the aforementioned states to another.

Each of the channel processing units includes a neural network which has been trained with a set of example input/result vector pairs. The example input/result vector pairs are generated by correlating actual information channel outputs with observed fatigue related events such as nodding off, head snapping, multiple blinks, blank stares, wide eyes, yawning, prolonged eyelid closures, and slow rolling eye movements.

Excerpts taken from this article are licensed under the GNU Free Documentation License. They use material from Wikipedia topics "Lucid Dream" and/or "Sleep".