When people are dreaming, their muscles do not move, even if in their dream they are moving. This is a natural process which prevents that people actually perform the movements they do in their sleep. In general, people are not aware of this inability to move, as it usually stops as soon as they wake up. People suffering from sleep paralysis wake up and find that they are unable to move. This is because the paralysis has not stopped. Usually it lasts for only a few minutes, and people have said they feel a "presence" or "ghost" during it.
Little is known about the physiology of sleep paralysis. However, some have suggested that it may be linked to post-synaptic (neurons sending signals to other neurons) inhibition (restraint) of nerves in the pons (back) region of the brain. In particular, low levels of melatonin may stop the depolarization current in the nerves, which stops stimulation of the muscles.
Hallucinations of ghosts, demons and Out of Body Experiences during sleep paralysis may be caused by a part of the brain called the parietal lobe (top-middle part of the brain), and by neurons known as mirror neurons.
Studies suggest that many people get sleep paralysis at least once in their lives. People who have narcolepsy often get it much more. Many people try to induce sleep paralysis, to have an Out of Body Experience.
There are few treatments available for sleep paralysis. One treatment is called Meditation-Relaxation Therapy. The treatment includes four steps: (1) one should close one's eyes and remind oneself that the experience is not dangerous in any way and common around the world; (2) and that since it is not dangerous one should not be afraid as that will only make the experience worse. (3) One should then focus very strongly on a positive thought or mental image (meditate); (4) and also relax ones muscles and avoid movement.
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