Sleep deprivation causes hyperactivity in the brain's near space network, responsible for alarm and caution signals.

“What we found was that the regions of the brain that are essentially an alarm network, which is a sort of a stay-away-from-me network that is sort of in the parietal cortex and the premotor cortex, it's sort of what we call the near space network. So it creates your comfort of boundary. And when objects start to approach you, it alarms to say, "Incoming. Be cautious. Be wary." That part of the brain became hyperactive when people were sleep-deprived.”