The transition from wakefulness to sleep is a progressive process that is reflected in the gradual loss of responsiveness, an alteration of cognitive functions, and a drastic shift in brain dynamics. These changes do not occur all at once. The sleep onset period (SOP) refers here to this period of transition between wakefulness and sleep. For example, although transitions of brain activity at sleep onset can occur within seconds in a given brain region, these changes occur at different time points across the brain, resulting in a SOP that can last several minutes. Likewise, the transition to sleep impacts cognitive and behavioral levels in a graded and staged fashion. It is often accompanied and preceded by a sensation of drowsiness and the subjective feeling of a need for sleep, also associated with specific physiological and behavioral signatures. To better characterize fluctuations in vigilance and the SOP, a multidimensional approach is thus warranted. Such a multidimensional approach could mitigate important limitations in the current classification of sleep, leading ultimately to better diagnoses and treatments of individuals with sleep and/or vigilance disorders. These insights could also be translated in real-life settings to either facilitate sleep onset in individuals with sleep difficulties or, on the contrary, prevent or control inappropriate sleep onsets.

中文翻译：

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困倦和从清醒到睡眠的过渡

从清醒到睡眠的转变是一个渐进的过程，反映在反应能力的逐渐丧失、认知功能的改变以及大脑动力学的急剧变化上。这些变化不会同时发生。睡眠开始期（SOP）在这里指的是清醒和睡眠之间的过渡期。例如，虽然给定大脑区域在入睡时大脑活动的转变可能在几秒钟内发生，但这些变化发生在整个大脑的不同时间点，导致 SOP 可能持续几分钟。同样，向睡眠的过渡会以分级和分阶段的方式影响认知和行为水平。它通常伴随或先于困倦感和需要睡眠的主观感觉，也与特定的生理和行为特征相关。为了更好地表征警惕性和 SOP 的波动，需要采用多维方法。这种多维方法可以减轻当前睡眠分类的重要局限性，最终为患有睡眠和/或警觉障碍的个体提供更好的诊断和治疗。这些见解也可以转化为现实生活环境，以促进有睡眠困难的个体入睡，或者相反，预防或控制不适当的入睡。