LiveScience explains some of the science behind the terrifying phenomenon of sleep paralysis.

One possible explanation could be that the hallucination is the brain’s way of clearing out confusion, when there’s a disturbance in the brain region that holds a neural map of the body or the “self,” according to a recent article that Jalal and his colleague Vilayanur Ramachandran, of UC San Diego, published in the journal Medical Hypotheses.

“Perhaps, in part of the brain, there’s a genetically hardwired image of the body — a template,” Jalal told Live Science. Previous studies have suggested that such a region may be a part of the parietal lobes, which are situated in the top-middle part of the brain.