A good night's sleep is restful for the amygdala, the brain's emotional centre. People who had recently awoken from sleep showed a decrease in reactivity in the amygdala after viewing emotional pictures, whereas those who had remained awake showed an increase.

Matthew Walker and his colleagues at the University of California, Berkeley, scanned the brains of volunteers as they looked at the pictures and rated the images' emotional intensity. The tests were repeated 12 hours later, after either a night of sleep or a wakeful daytime period. The most intense emotional ratings decreased among those who had slept, but not in those who had not slept. These decreases in amygdala reactivity and emotional ratings correlated with declines in electrical activity in the brain during rapid eye movement (REM) sleep.

The findings could explain why people with anxiety disorders, who often have abnormal REM sleep, are more emotionally reactive.

Curr. Biol. http://dx.doi.org/10.1016/j.cub.2011.10.052 (2011)