Figure 1.

The relationship between sleep and ambient temperature.

a, The changing relationship of skin to core temperature as mice approach the thermoneutral zone (TNZ). This has similarities to the distal-proximal gradient in humans where vasodilation in distal regions increases peripheral skin temperature and facilitates heat redistribution from the core. Having reached the cooler night-time temperature, the formation and maintenance of warm microclimates minimises energy loss while maintaining vasodilation. b, The structure of sleep is sensitive to ambient temperature. In mice, increasing ambient temperature promotes NREM sleep until the upper threshold of the thermoneutral zone where it declines sharply most likely due to heat stress. REM sleep is maximised in a narrow thermal window that appears to align with the TNZ. It should be noted that the thermoneutral pulsing method employed in [9] did not fully replicate warm-induced increases in NREM sleep. Adapted from [9,18,28,53,57,62].