Investigating the neurophysiological basis of sleep quality

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We spend about one third of our life asleep, yet we still do not know why sleep is necessary. The importance of sleep becomes especially apparent in primary sleep disorders such as insomnia, as well as in many other diseases associated with poor sleep. When we do not get sufficient sleep our mood worsens, we make more errors, we have a hard time focusing our attention and make poor judgments. Moreover, poor sleep is often a root cause of major accidents such as Chernobyl, Clapham Junction rail crash, the Challenger, Exxon Valdez oil spill and other tragedies, where sleep loss affected misjudgements probably happened. The UK Health and Safety Executive (HSE) makes the point that fatigue can lead to errors and accidents, ill-health and injury, and reduced productivity and has also been implicated in 20% of accidents on major UK roads and is said to cost the UK £115 - £240 million per year in terms of work accidents alone. If we go to the doctor with a complaint about sleep problems or associated cognitive deficits while we are awake, we are usually asked to convey our subjective account in some form of an "analogue" scale that may result in an inaccurate assessment. Indeed, while "sleep quality" is a concept widely used in clinical practice, it is defined only vaguely and often only in qualitative terms. Existing quantitative measures of sleep quality, such as a total duration of sleep, measured with polysomnography, while useful in some cases, may often appear not adequate as there is a large variation of sleep parameters from patient to patient and these measures do not correlate well with the patient's experience. Inaccurate assessment of sleep quality may lead to errors in diagnostics, and inadequate or inefficient treatment. The aim of the current project is to provide an in-depth investigation of the factors that determine sleep quality, focusing for the first time on the electrical activity of many individual cells in the brain. The research strategy we intend to adopt for the current project is based on the recently established concept of "local sleep", according to which some parts of the brain can be "asleep" while other are "awake" at the same time. This pattern of activity may be very useful, because it would allow some parts of the brain to take rest while others continue to work, but in some cases it may be very disruptive for brain function. For example, under certain conditions, some areas of our brain may be unable to "fall asleep" and remain in a "local wakefulness" state, resulting in us experiencing a very bad nights sleep even though from a behavioural perspective or when the brain waves are measured at the level of the scalp, it seems as if we have been asleep all night. The inability to obtain restorative sleep during the night, may, in turn, lead to an intrusion of brief episodes of "local sleep" during the day, resulting in overall poor wake quality, as manifested in attention lapses and many other cognitive deficits.Therefore our hypothesis is that sleep quality, both in terms of how refreshed we feel in the morning and how well we perform during the day, depends precisely on how much local sleep and local wake occurred in our brain during the night. Testing this hypothesis will be crucial for improving the recognition and treatment of sleep disorders of various origins.