During sleep we experience two patterns of sleep namely non- REM sleep (randomised eye movement) and REM sleep, which follow one another in episodes. During the REM sleep, some of the brain regions remain active, so it is also known as “paradoxical sleep.”
Disorders of REM sleep include, sleep paralysis and catalepsy. During sleep paralysis, the person is paralyzed, awakens and experiences fear. During catalepsy patients appear like a corpse and their body freezes.
Thus, the blank can be filled with sleep paralysis; catalepsy.