Sleep Paralysis
Sometimes a person has certain terrifying things happen to them at night. All of us have had dreams when a terrifying monster comes at us and we are paralyzed and unable to run away. These dreams can be more real at times and take on the qualities of a vision. They can appear to take place in an altered state that is somewhere between waking and sleep. When they do, they become very disturbing. Especially for people who are extremely religious or superstitious they can seem to be some evil force from outside our world intruding upon our realm. But studies have shown that they are a natural phenomenon of the sleep process, although in some cases they may point to a problem.
When a person goes to sleep and begins to dream, the brain sends a signal to the muscles of the body that causes them not to respond to motor signals. This keeps the body from acting out the dreams that a person experiences. This is usually not noticeable, because the brain simulates the actions of the body in dreams. Sometimes, however, a person is caught in between sleeping and waking. They experienced a frightening dream and try to initiate actions to flee the situation. Because the brain continues to immobilize their muscles, they have an alarming sense of paralysis. These experiences are especially disturbing when a person is falling asleep or in the process of waking. The person may dream that they have awakened to a terrible experience, or may actually be semi-conscious and in a state similar to lucid dreaming, but without the awareness that they are in a partial dream state. In this state they may experience hallucinations, and they usually involve the presence of something evil in the room with them. They may see this evil entity very clearly in the dream portion of their hallucination, or may only sense its presence. Most of the abduction by aliens stories can be explained by these types of hallucinations. People can also deduce that they are being assaulted by an evil spirit or demon during these episodes. Because the person has awakened suddenly, the brain keeps the body paralyzed and even continues to carry on the creation of virtual experiences, even though the person has opened their eyes. The experience can therefore seem very real and be very frightening. They may experience the hallucination with all of their senses. Most people, however, after waking realize from the content of their experience that it could not have been real.
These hallucinations are grouped into three categories: hypnagogic hallucinations which occur when a person is falling asleep, hypnapomnic hallucinations which occur when a person is in the process of waking up, and isolated sleep paralysis which can occur any time during the night. The first two categories can point to the possibility of a problem. Hypnapomnic and hypnagogic hallucinations can be caused by narcolepsy. Other symptoms of narcolepsy are excessive daytime sleepiness (EDS), cataplexy, and automatic behavior. EDS or excessive daytime sleepiness can occur even after sufficient sleep. A person with EDS can fall asleep suddenly and often during the day. The refreshing benefits of the nap are short lived. In addition, the person may sleep fitfully during the night.
Cataplexy is characterized by the recurring loss of muscle function during the day. It may be preceded by an episode of sudden emotional reaction which may last a minute or more and is followed by a weakness in muscle function all the way to a total bodily collapse. The person remains conscious through this episode, although they may fall asleep after them and sleep for a prolonged period. Because cataplexy is considered to be only associated with narcolepsy, it makes the diagnosis relatively easy. These attacks usually take place when the person is tired.
Automatic Behavior is the state where a person carries out an act, but without consciousness. It is a literal "the lights are on, but nobody is home" state. This behavior can be indicative of other problems, but it also is more prevalent when the subject is tired. All of us have probably experienced something similar when driving on a straight stretch of road late at night. We suddenly realize that we have no remembrance of driving the last ten miles. Our mind has taken a little break and switched on the autopilot.
The other kind of sleep paralysis is isolated sleep paralysis. It is a type of nightmare and can occur any time of the night. Most people will experience this type of bad dream occasionally, but should not be alarmed but realize that they have experienced a bad dream, although it may be more real and frightening than the normal bad dream.