Sweet Dreams

Dreaming of a good night’s sleep?

This is Sandra Tsing Loh with the Loh Down on Science.

Feeling tired–and awful?? You’re not alone! Dreaming, also called rapid eye movement or REM sleep, is important for health. And poor REM sleep has been linked to problems like Alzheimer’s disease!

Enter Chia-Jung Tsai and colleagues at the University of Tsukuba in Japan. They wondered — how does dreaming keep our brains in balance?

First, they injected twelve mice with dye to light up their blood vessels. Then they put the critters under a strong microscope to see individual blood cells. They measured blood flow through the glowing brain veins for both awake and sleeping mice. 


Blood flow was about the same in mice who were awake or in non-REM sleep. But during REM sleep, around TWICE as much blood rushed through their mousey brains! 

The team believes while we dream, this surge of blood helps wash out and refresh the brain. Finding ways to stimulate this clean-up job could lead to treatments for some brain disorders.

Time for a power wash… I mean power nap!

Reference: Tsai, C., Nagata, T., Liu, C. et al. Cerebral capillary blood flow upsurge during REM sleep is mediated by A2a receptors. Cell Reports, 36(7) (2021). https://doi.org/10.1016/j.celrep.2021.109558