Another Explanation for Hallucination during Sleep Paralysis: Mismatch between Brain’s Expectation and Sensory Input

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Biology 202
2000 Third Web Report
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Another Explanation for Hallucination during Sleep Paralysis: Mismatch between Brain’s Expectation and Sensory Input

Hiro Takahashi

In this web research, I have pursued the second hypothesis of my previous web paper that the corollary discharge signals may trigger hallucination during sleep paralysis (1). This time, I have hypothesized that mismatch between internal expectation and sensory input causes increased level of serotonin and thus, higher blood pressure in the brain, which then induces hallucination. For evidences to support my guess, I have made a connection between hallucination and motion sickness because the current science supports that motion sickness results from mistracking of the sensory information in the brain. These two situations seem very unrelated, for one centers around perception of unreal existence, and the other involves nausea and vomiting. Nevertheless, I have found a similarity that both brain confusion requires a high level of serotonin. As a consequence of the comparison, I have concluded that the conflict in the brain can stimulate hallucination during sleep paralysis.

In my second web paper, I have suggested a possibility that corollary discharge signals trigger hallucination during sleep paralysis (1). As a victim finds himself under total paralysis, he struggles to escape the uncomfortable, fearful condition. His I-function in the brain sends the activator signals to the skeletal muscles in the limbs. At the same time, the I-function issues corollary discharge signals to other parts of the brain, telling them about the command sent to the muscles. Because of the corollary discharge signal, the brain expects a certain motor symphony produced by the muscles. In a usual circumstances, the internal expectation matches the sensory input from the muscles, informing of its position and movement. However in an episode of sleep paralysis, the skeletal muscles cannot move, and the brain receives a different sensory input from what it has expected. For one of my hypothesis in the last paper, I have proposed that this mismatch in the brain somehow causes hallucination during sleep paralysis (1). The neurological aspects of motion sickness provide some supports for my hypothesis because in the present scientific view, nausea and vomiting in a moving vehicle result from the mismatch in the brain. Motion sickness, commonly associated with symptoms like headache, nausea, and vomiting, takes place in a moving vehicle, including a space ship. According to NASA, about 2/3 of the astronauts experience it shortly after entry to the orbit because of the loss of gravitational field (2). Within the Earth's gravitational field, vestibular system in the inner ear senses the direction of the force and uses the information, along with the visual and other inputs, to interpret the head and body position (2), (3). However in a zero-gravitational field, vestibular system cannot feel the gravity and sends the brain different signals from visual and other sensory inputs (2), (3). This set of different sensory inputs does not match with any of the previously stored neural patterns, and the brain interprets this mistracking as the effects of neurotoxins (2), (4). Consequently, the brain triggers vomiting as a defense mechanism to expel the poisons from the stomach, into which the toxins have possibly entered with food (4), (6).

Hallucination and motion sickness seem very different, but a neurotransmitter serotonin links them together. Serotonin affects various conditions in one's body, such as emotions, sleep cycles, pituitary hormone secretion, appetite control, and pain perception (6), (7), (8), (9). The most important function for motion sickness is appetite control. After each meal, individual's glucose concentration in blood increases, and high blood sugar level stimulates the release of insulin, which then increases the brain level of the amino acid tryptophan, a serotonin precursor (6), (7). High serotonin concentration decreases one's desire to eat because sugar consumption is unnecessary when the glucose level is high (6), (7). Nausea and vomiting usually occurs when one overeats, hence when the blood sugar and serotonin concentrations are extremely high. Similarly, even without overeating, nausea and vomiting in motion sickness may result from abnormally high serotonin level. When the mismatch happens in the brain, the alarmed brain misunderstands that some poisonous agents have entered the stomach, and it probably signals to release more serotonin to induce vomiting so that the toxin will exit the body. As well as in vomiting, the release of serotonin is necessary in inducing hallucination during sleep paralysis. In addition to the functions described the previous paragraph, serotonin causes the smooth muscles of blood vessels to constrict and raises the blood pressure (8), (10). When the blood pressure increases in the brain, the membrane potential in the optic/auditory cortex change, and triggers hallucination. In the last paper, my main hypothesis has focused on fear as the major hallucination-stimulating factor, for it stimulates fight-or-flight response and release of serotonin (1). And yet, because the brain's confused state in motion sickness establishes high serotonin level in the body, the increased serotonin concentration in hallucination during sleep paralysis may also follow the mismatch between internal expectation and sensory input.

My hypothesis suggests that hallucination during sleep paralysis and motion sickness both involve in confusion in the brain and consequently, an increase in serotonin level; however the outcome differs in these cases. The lack of vomiting in a sleep paralysis episode may be due to the neural inhibitors, which prevents the major muscle movements from acting out a dream. When one vomits, the windpipe closes, and the muscles on abdominal wall and diaphragm produces a sudden and forceful contraction (11). This muscle tightening constricts the stomach and cause it to empty acid chyme, partially digested food, upwards (11). In a person experiencing sleep paralysis, the brain may issue inhibitors not only to the muscles in the limbs but also to the abdominal and diaphragm muscles, restricting their activities only to breathing. As a result, the sudden contraction cannot happen, and the sleeper does not vomit. During sleep stage, the brain may also inactivate the abdominal muscles in order to directly keep one from vomiting so that a sleeper does not choke on his own vomit and die, like some intoxicated people do. During sleep paralysis, hallucination may occur as an alternative response to the high serotonin concentration in the body because of a limited amount of blood flow allowed in the paralyzed body. For the muscles do not move, they require less oxygen and hence, less blood flow. Also, some parts of the brain that is still in REM sleep stage may restrict the blood flow in the major muscles to prevent them from being activated during a dream. As a result, the high serotonin has an increased effect on the active brain, in which the blood pressure increases greatly and suddenly, inducing hallucination.

I have concluded that the mismatching set of sensory input and internal expectation can trigger hallucination in sleep paralysis. However, there may be more different mechanisms that stimulates serotonin release and/or high blood pressure. Besides, there may be more factors other than high blood pressure in the brain that changes the membrane potential in visual/auditory cortex. Understanding the mechanism of hallucination and/or sleep paralysis will lead to discovery of treatment. If hallucination arises in the same way as motion sickness, artificially induced and repetitive experience of sleep paralysis may reduce hallucinatory episodes, for a person's brain can adapt to the neural confusion, as an astronauts overcome motion sickness after several days. If sleep paralysis is really a hereditary disorder as a web page "Evil's Sleep Paralysis" (12) suggests, finding the responsible genes will provide a major access to the cure of the patients. Although sleep paralysis and the associating hallucination do not bring any harm to the victims, discovery of an effective treatment will free them from the fearful experiences. Moreover, a scientific approach to cure the sleep paralysis patients will change the religious or supernatural components of a society. If people gain a knowledge that sleep paralysis and hallucinations are medically treatable, many will lose belief in the existence of gods and/or ghosts. Thus, discovery of scientific treatment for sleep paralysis and hallucination will save the sufferers, but it may bring destruction of very religious bound societies around the world.


WWW Sources

1)Fear-Induced Hallucination: How Sleep Paralysis Triggers Hallucination, my second web paper

2)Space Neuroscience, by NASA

3)Weightlessness and the Human Body, an article by Ronald J. White in Scientific American

4)Autism Science: Cerebellum and the Tracking Module

5)Is Nausea in Pregnancy Nature's Way of Protecting the Fetus from Toxins?, by Rick Weiss

6)Serotonin and Eating Disorders, from Medical Sciences Bulletin, October 1994

7)About 5-HTP, from the Natural Health Company

8)Background Information about Psychedelic Drugs

9)Unlocking the Secrets of Serotonin, by Thrive On Line

10)The Neurologic System, by J. F. Ripka and F. T. Ripka, BioSyn site

11)Nausea and Vomiting, quick facts on nausea and Vomiting

12)The Evil's of Sleep Paralysis

13)Sleep Paralysis: Awake But Still Asleep, my first web paper on Sleep Paralysis



Comments made prior to 2007

i would like to know , why my doctor cannont explain my bad hallucanegenic dreams , and not explain why i have long lingering headaches , like being on a roundabout ? . it is like ? my brain isnt moving at same speed as earth ? 173.000 mph per hour . can brain gravity explain what you are describing ? . my depression is a mostly dark occcuring problem , maybee less gravity during dark phases of earth ? . could that explain matter/gravity flow in a light /dark matter ? ... Allan Drummond, 16 March 2006



Hello . This info has become very helpful in knowing exactly what is happening to me. These Sleep Paralysis have been very terrorfying. How do i treat it? Strangly enough my first real terrorfying attack started right before i turned 30 years. Very uncommon according to info. I have had narcolepsy since i was about 15 years. These Paralysis attacks have been reaccuring every year now . LIke around my birthday. . I feel like i want to die something. Help me find a treatment ... Faheem Munir, 27 February 2007


D. Feauto's picture

relationship between inner ear and sleep paralysis

My husband has recently been diagnosed with an arachnoid cyst on the 7th and 8th nerve in the inner ear. Over the last few years, he has had a lot of problems with vertigo, motion sickness, etc. which we now know is due to this cyst. Also during the last few years, he has experienced sleep paralysis on several occasions. It is interesting to note that as the cyst has grown, his vertigo/motion sickness/headaches have drastically increased, and so have his episodes of sleep paralysis. Your article backs up my theory that these episodes are also due to this cyst. He will have having surgery in 8 weeks to drain the cyst, and I am hopeful that the sleep paralysis will stop as a result. Very good article, thank you.

Serendip Visitor's picture

Theory doesn't add up

It's true what you said that basically mitch-matched brain signals should produce a predictable result such as muscle restrictions ect which is true. But that has no bearing on the actual hallucination itself. Over a million people have reported seeing similar demons in their sleep (including myself). What are the odds that if a million people were marching through the desert and began to hallucinate, we'd all not only have negative visions (instead of positive ones like finding water), but that we all report similar sightings with the SAME physical restrictions on the SAME parts of the body? Similar than the chances of winning the Lotto I would think. Here is a link to my personal experience and what I did to cure it.

Anonymous's picture


okay i know this is 2010 and do not know if anyone reads this but i have been plagued with nightmares my whole life. vivid, frightening and very detailed, [in fact i can still describe in detail dreams from when i was a child] as an adult i have and am currently experiencing hallucinations, visual and auditory as i am falling asleep for going on one month now. i am now experiencing nausea and vomiting for the past two weeks. last month i stopped taking my sertraline for depression. could this be related?? years ago i experienced sleep paralysis on a regular basis but thought it was interesting all the things are related in informative writings.

nichola spencer's picture

my 7yr old daughter

my daughter Kobe had been on a trip with her dad to alton towers travelling from braford.kobe didn't have anything out of the ordinary that day to eat or drink and wasn't taking any medications at the time. Back home in bradford kobe's dad and step-mum settled the kids in bed and went to bed themselves. Around midnight kobe woke for a drink and had a little sip of red bull,not much, then went back to sleep. Around 12.30pm kobe awoke hysterical saying people was behind the curtains and that ther was people in the house with weapons(knifes) and wanted to hurt her, kobe's dad and stepmum was still asleep. Kobe was frightened and didn't want to stay in the house and let herself out,she was out of the house for around 2&half by herself and was found at edge of woods near her dads house. no-one knows what actually happened to her,she was taking to hospital and drug tested but all tests came back negative since then kobe's attitude towards everything in life has changed i lost my buddy thaqt night and cant help her as i wasn't there,she cant remember what happened to her in the hours she was out of the house, how do i help her and what caused this to happen,

Ness from Onett, Eagleland's picture

The situation with Kobe

The situation with Kobe seems quite unusual, as SP mostly occurs in adolescents and adults. Nevertheless I can tell you nothing has happened her, it is all in her mind.
Sadly modern medicine aka medical techniques explained using the scientific method offer no held in the field of SP, a phenomenon that have occurred for ages.
What really caught my attention was that you mentioned your daughter ingesting Red Bull before experiencing hallucinations, earlier tonight I have also drank a Red Bull and I just experienced and episode of SP, my hallucination was that I was taken aboard a space ship. Because of the realness of these hallucinations some people even claim they really have happened.
My personal theory is that the hallucination are what our deepest fears are. Hostile extra-terrestrial aliens are my worst fear, although I doubt they exist and I guess for a little girl, strangers with knives are her greatest fears. And her reaction is typical of her personality as well, because after experiencing SP, you cannot simply go back to sleep because of the fear you feel. As you can see I type blurps on the internet because I cannot go back to sleep. But for a little girl 12 years my junior an irrational reaction is typical.

I hypothesize that she will return to normal soon without any help from doctors. Because they will tell you there is nothing wrong with her as they have no methods of detecting her neuroactivitivities. Some bad doctors will even administer psychoactive drugs to her, as a quick fix...the reality is that drugs will make a mountain out of a molehill...

There is nothing wrong with her only that she is now really scared and fear changes all. To uncared her you can either just talk it out with her and explain SP to her. Alternative you can seek a shrink (they are generally quite nice people) or get Chinese Herbal Medicine to help her condition.
Shrinks are great if your insurance covers it but if not be prepared to pay around 150-200/hour of talking.

Chinese medicine with acupuncture (on the head) have helped me with SP as well. Chinese medicine as opposed to many other holistic methods of curing ailements is what I would like to call semi-scientific: meaning many of the techniques could be partially proved by science, perhaps because technology is not advance enough to prove it or perhaps because of poor documentation. Several concepts such as the Yin and Yang and Qi are quite philosophical. Recent development in nuclear physics, nanotechnology and quantum mechanics all proved many theories the Chinese had for thousands of years.

One last thing: never let a child near Red Bull again, there is a reason there is a warning on Red Bull saying that it is for adults only.

gopala krishna. gadi's picture


I WOULD APPRECIATE IF YOU COULD EXPLAIN THE CONNECTION BETWEEN SLEEP & GRAVITATIONAL FIELD . THE SLEEPING POSTURE IS ALLWAYS HORIZONTAL .Human beings liedown for sleeping There is no sleeping in the vertical posture. Why sleep demands lowest potential energy state?

Jennifer's picture

connection between sleep & gravitational field

I can point out a few things that might help you-

1. A human can infact sleep in the vertical posture. I have narcolepsy with cataplexy, and I have experienced full REM sleep while standing. The attacks don't last long enough for me to fall, but cause me to jump in the inside when waking (thats how I know I've been asleep because I don't even realize it.)
2. Rem sleep causes all the muscles in your body to relax and that could be why a humans need to be horizontal for extended time periods of sleep.

Kathy's picture

working while standing asleep

If I go to the bathroom or to get something to drink I will fall asleep befour I get there.
I talk and think I am some where else.I also do this as I am falling asleep,talking that is.
My husband hates this and if he catches me he yells as load as he can my name.
I about fall and fill like my heart stops.
Now I am talking during the day with my eyes closed.I go off telling some kind of story that does not make any since.
HELP what do I do?
I totaled my car by hitting a power pole and everyone in the family says I fell asleep but I think I passed out.
The reason is I opened my eyes as I was hitting the pole and could not do anything about it.

sincity's picture

night terror

Hi my name is Geraldine but everyone calls me sin or sincity, anyways i discovered sleep paralysis four years ago. I just recently had an crazy experience a couple of nights ago. i was in my room dabating if i wanted to watch comic veiw or go to be, but for some reason i felt so scaird to go to bed, so a couple of minutes pass by and i nodded off, i was fine until i felt someone was pinning my chest down i couldnt move and it was hard for me to breath. i felt this warm energy benefe my body i couldnt believe i was fucking ten inches from floating on my bed i was scaird shitless.... i couldnt yell couldnt talk or do anything. the only thing i could do was move my eyes and blank. it last for a few seconds but seem like forever. now this was the first time floating any other time i hear shit and see shit but me floating that shit was spooky. after that was over my body stay warm for about ten minutes. that something i dont ever wont to experience agian.......... please help me ....

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