Decreasing sleep requirement with increasing numbers of neurons as a driver for bigger brains and bodies in mammalian evolution
Decreasing sleep requirement with increasing numbers of neurons as a driver for bigger brains and bodies in mammalian evolution
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DOI：
10.1098/rspb.2015.1853
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发表时间：
2015-10-07
影响因子：
4.7
通讯作者：
Herculano-Houzel, Suzana
中科院分区：
文献类型：
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作者：
Herculano-Houzel, Suzana
哺乳动物的睡眠时间为3 ~ 20 h d（-1），但究竟是什么调节了每天的睡眠需求还不清楚。虽然哺乳动物进化的特点是倾向于更大的身体和大脑，但维持更大的身体和大脑需要每天增加进食时间，这与大量的睡眠需求不相容。因此，哺乳动物的进化必然涉及将身体和大脑尺寸的增加与睡眠需求的减少联系起来的机制。在这里，我表明，每天的睡眠需求减少，在哺乳动物物种和大鼠出生后的发展与皮质神经元密度和表面积之间的比例下降，这可能会导致睡眠诱导代谢物积累更慢的实质。由于在哺乳动物进化过程中，非灵长类动物皮层的神经元增加降低了这一比例，我认为皮层神经元数量的增加导致了进化过程中睡眠需求的减少，从而允许更多的进食时间和体重的增加，这将通过每小时更大的热量摄入促进大脑神经元数量的进一步增加。因此，神经元数量的增加与睡眠需求的减少和进食时间的增加相结合，可能不仅允许而且推动了哺乳动物进化中大脑和身体质量增加的趋势。
Mammals sleep between 3 and 20 h d(-1), but what regulates daily sleep requirement is unknown. While mammalian evolution has been characterized by a tendency towards larger bodies and brains, sustaining larger bodies and brains requires increasing hours of feeding per day, which is incompatible with a large sleep requirement. Mammalian evolution, therefore, must involve mechanisms that tie increasing body and brain size to decreasing sleep requirements. Here I show that daily sleep requirement decreases across mammalian species and in rat postnatal development with a decreasing ratio between cortical neuronal density and surface area, which presumably causes sleep-inducing metabolites to accumulate more slowly in the parenchyma. Because addition of neurons to the non-primate cortex in mammalian evolution decreases this ratio, I propose that increasing numbers of cortical neurons led to decreased sleep requirement in evolution that allowed for more hours of feeding and increased body mass, which would then facilitate further increases in numbers of brain neurons through a larger caloric intake per hour. Coupling of increasing numbers of neurons to decreasing sleep requirement and increasing hours of feeding thus may have not only allowed but also driven the trend of increasing brain and body mass in mammalian evolution.