A structure located in the left and right sides of the brain, called the amygdalaa key hot spot for triggering strong emotions such as anger and rage, and linked to the fight-or-flight responseshowed well over a 60 percent amplification in emotional reactivity in the participants who were sleep-deprived. In contrast, the brain scans of those individuals who were given a full nights sleep evinced a controlled, modest degree of reactivity in the amygdala, despite viewing the very same images. It was as though, without sleep, our brain reverts to a primitive pattern of uncontrolled reactivity. We produce unmetered, inappropriate emotional reactions, and are unable to place events into a broader or considered context.

Why We Sleep by Matthew Walker