Ever feel so bushwhacked that you tell someone you’re “half asleep”? Well, it turns out you probably were. Researchers have found that parts of your brain actually do turn off when you’re fatigued—sometimes even before you’re consciously aware that you’re tired, according to a new study. These slumbering neurons can cause small errors or brain farts, like putting the milk in the cupboard and the cereal in the fridge, the Telegraph reports.
“We have seen with EEGs that even while we are awake, we can experience short periods of 'micro sleep,’” the study’s author says. Researchers performed the test by inserting probes in the brains of rats, then keeping them awake for prolonged periods. After a while, even though the rats were still moving about and seemingly awake, the probes showed parts of their brains as asleep. When that happened, the rats tended to botch complicated tasks, like grabbing sugar pellets with their paws.