Finally there may be some people who experience full-blown hallucinations during sleep paralysis in which they not only have vivid and complex imaginative experiences but are also convinced that these experiences have objective external sources. Such people are unlikely to describe their experience as one of sleep paralysis but perhaps as one of demon possession or alien abduction. It is entirely possibly that almost everyone has experienced such a state but has scarcely noticed and soon forgotten the experience. Another two-thirds of those experiencing sleep paralysis, however, have associated experiences sometimes referred to as hypnagogic and hypnopompic hallucinations. These hallucinations may be tactile, kinesthetic, visual, or auditory.
Individuals vary considerably in the extent to which they report such symptoms.
Specifically, PREM is characterized by bursts of rapid eye and middle ear movements and characteristic cortical and hippocampal EEG patterns. One likely function of the general atonia is the prevention of the physical enactment of the motor components of dreaming. There are at least two major traditional hypotheses concerning the connection between neurophysiological events and visual imagery in dreams. The neurotransmitters in this region have not been clearly determined, but are neither cholinergic nor monoaminergic. These populations are hypthesized to interact with REM-off noradrenergic neurons in the locus ceruleus and seratonergic neurons in the raphe system.