Investigating the neurophysiological basis of sleep quality

我们一生中大约三分之一的时间都在睡觉，但我们仍然不知道为什么睡眠是必要的。睡眠的重要性在失眠等原发性睡眠障碍以及许多其他与睡眠不足有关的疾病中尤为明显。当我们没有得到充足的睡眠时，我们的情绪会恶化，我们会犯更多的错误，我们很难集中注意力，做出糟糕的判断。此外，睡眠不足往往是重大事故的根本原因，如切尔诺贝利、克拉彭枢纽铁路事故、挑战者号、埃克森·瓦尔迪兹号石油泄漏和其他悲剧，在这些事故中，睡眠不足可能会导致错误判断的发生。英国健康与安全执行局（HSE）指出，疲劳会导致错误和事故、健康不良和伤害，并降低生产力，英国主要道路上20%的事故也与疲劳有关，据说仅工伤事故每年就给英国造成1.15亿至2.4亿英镑的损失。如果我们在醒着的时候抱怨睡眠问题或相关的认知缺陷去看医生，我们通常会被要求以某种形式的“模拟”量表传达我们的主观描述，这可能会导致不准确的评估。事实上，虽然“睡眠质量”是临床实践中广泛使用的一个概念，但它的定义却很模糊，而且往往只是定性的。现有的睡眠质量定量测量方法，如用多导睡眠图测量的总睡眠时间，虽然在某些情况下是有用的，但由于患者之间的睡眠参数差异很大，这些测量方法与患者的经验不太相关，因此往往显得不够充分。对睡眠质量的不准确评估可能导致诊断错误，以及治疗不充分或无效。当前项目的目的是对决定睡眠质量的因素进行深入研究，首次将重点放在大脑中许多单个细胞的电活动上。我们打算在当前项目中采用的研究策略是基于最近建立的“局部睡眠”概念，根据该概念，大脑的某些部分可以“睡着”，而其他部分同时“醒着”。这种活动模式可能非常有用，因为它可以让大脑的某些部分休息，而其他部分继续工作，但在某些情况下，它可能会对大脑功能造成严重破坏。例如，在某些情况下，我们大脑的某些区域可能无法“入睡”，并保持“局部清醒”状态，导致我们经历一个非常糟糕的睡眠，即使从行为的角度来看，或者当脑电波在头皮的水平上测量时，我们似乎已经睡了一整夜。在夜间无法获得恢复性睡眠，可能反过来导致白天短暂的“局部睡眠”的侵入，导致整体清醒质量差，表现为注意力缺失和许多其他认知缺陷。因此，我们的假设是，睡眠质量，无论是我们早上有多神清气爽，还是我们白天的表现有多好，都取决于我们大脑在夜间局部睡眠和局部清醒的程度。验证这一假设对于提高对各种原因的睡眠障碍的认识和治疗至关重要。

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.