Avian Sleep Group, Max Planck Institute for Biological Intelligence, Seewiesen, Germany.
Department of Biopsychology, Institute of Cognitive Neuroscience, Faculty of Psychology, Ruhr-University Bochum, Bochum, Germany.
Nat Commun. 2023 Jun 5;14(1):3259. doi: 10.1038/s41467-023-38669-1.
Mammalian sleep has been implicated in maintaining a healthy extracellular environment in the brain. During wakefulness, neuronal activity leads to the accumulation of toxic proteins, which the glymphatic system is thought to clear by flushing cerebral spinal fluid (CSF) through the brain. In mice, this process occurs during non-rapid eye movement (NREM) sleep. In humans, ventricular CSF flow has also been shown to increase during NREM sleep, as visualized using functional magnetic resonance imaging (fMRI). The link between sleep and CSF flow has not been studied in birds before. Using fMRI of naturally sleeping pigeons, we show that REM sleep, a paradoxical state with wake-like brain activity, is accompanied by the activation of brain regions involved in processing visual information, including optic flow during flight. We further demonstrate that ventricular CSF flow increases during NREM sleep, relative to wakefulness, but drops sharply during REM sleep. Consequently, functions linked to brain activation during REM sleep might come at the expense of waste clearance during NREM sleep.
哺乳动物的睡眠被认为有助于维持大脑内健康的细胞外环境。在清醒状态下，神经元活动会导致有毒蛋白质的积累，人们认为脑脊髓液（CSF）通过脑脊液压通过大脑来清除这些蛋白质。在老鼠中，这个过程发生在非快速眼动（NREM）睡眠期间。在人类中，也已经通过功能磁共振成像（fMRI）显示，在 NREM 睡眠期间，脑室 CSF 流动增加。在鸟类中，睡眠和 CSF 流动之间的联系以前尚未得到研究。通过对自然睡眠的鸽子进行 fMRI 研究，我们发现 REM 睡眠是一种与清醒状态相似的大脑活动的矛盾状态，伴随着与处理视觉信息相关的大脑区域的激活，包括飞行中的光流。我们进一步证明，与清醒状态相比，NREM 睡眠期间脑室 CSF 流动增加，但在 REM 睡眠期间急剧下降。因此，与 REM 睡眠期间大脑激活相关的功能可能是以 NREM 睡眠期间废物清除为代价的。
