Oniz Adile, Inanc Gonca, Taslica Serhat, Guducu Cagdas, Ozgoren Murat
Department of Biophysics, Faculty of Medicine, Dokuz Eylul University, Izmir, Turkey.
Sleep and Conscious States Technology Research and Application Center, Izmir, Turkey.
Front Hum Neurosci. 2019 May 14;13:160. doi: 10.3389/fnhum.2019.00160. eCollection 2019.
Sleep is a very critical process that constitutes up to one third of daytime of a healthy adult. It is known to be an active period where body and brain is refreshed for the next day. It is both part of a larger cycle, i.e., circadian rhythm, and has subcsycles in it, i.e., sleep stages. Although hemodynamics of these stages have been investigated especially in the last two decades, there are still points in the hemodynamics to be illuminated especially in terms of refreshment. This study aims to investigate refreshing property of sleep in terms of sleep stages using functional near-infrared spectroscopy (fNIRS) for measuring prefrontal cortex (PFC) hemodynamics. Nine healthy subjects slept in sleep laboratories, monitored by polysomnography and fNIRS before, during, and after night sleep. REM stage had lower oxyhemoglobin (HbO) and total hemoglobin (HbT) than the other sleep stages and wakefulness. Deoxyhemoglobin (HbR) did not differ between any stages. All sleep stages and wakefulness stage at the end of the sleep had higher HbO and lower HbR than the beginning of the sleep. HbT levels did not differ between the beginning and the end of the sleep for any stages. During REM sleep, PFC seems to get lower blood supply, possibly due to increased demand in other brain regions. Regardless of the stage, PFC has higher oxygenation toward the end of sleep, indicating refreshment. Overall, our brain seems to be on duty during sleep throughout the night for "cleaning" and "refreshing" itself. Hemodynamic changes from the beginning to end of sleep might be the indicator of this work. Thus, accordingly REM stage seems to be at a central point for this work.
睡眠是一个非常关键的过程，对于健康成年人来说，睡眠时间占一天中的三分之一。众所周知，睡眠是一个活跃期，身体和大脑在这个时期得到恢复，为第二天做好准备。它既是一个更大周期（即昼夜节律）的一部分，其本身也有子周期（即睡眠阶段）。尽管在过去二十年里，人们尤其对这些睡眠阶段的血液动力学进行了研究，但在血液动力学方面仍有一些问题有待阐明，特别是在恢复方面。本研究旨在使用功能近红外光谱技术（fNIRS）测量前额叶皮层（PFC）的血液动力学，从睡眠阶段的角度研究睡眠的恢复特性。九名健康受试者在睡眠实验室睡觉，在夜间睡眠前、睡眠中和睡眠后通过多导睡眠图和fNIRS进行监测。快速眼动（REM）阶段的氧合血红蛋白（HbO）和总血红蛋白（HbT）低于其他睡眠阶段和清醒状态。脱氧血红蛋白（HbR）在任何阶段之间没有差异。睡眠结束时所有睡眠阶段和清醒阶段的HbO均高于睡眠开始时，HbR则低于睡眠开始时。任何阶段睡眠开始和结束时的HbT水平没有差异。在REM睡眠期间，PFC的血液供应似乎较低，这可能是由于其他脑区需求增加所致。无论处于哪个阶段，睡眠结束时PFC的氧合水平更高，表明大脑得到了恢复。总体而言，我们的大脑似乎在整个夜间睡眠期间都在“清洁”和“恢复”自身。从睡眠开始到结束的血液动力学变化可能是这项工作的指标。因此，相应地，REM阶段似乎在这项工作中处于核心地位。
