Hypnopompia (also known as hypnopompic state) is the state of consciousness leading out of

sleep Sleep is a sedentary state of mind and body. It is characterized by altered consciousness, relatively inhibited sensory activity, reduced muscle activity and reduced interactions with surroundings. It is distinguished from wakefulness by a de ...

, a term coined by the psychical researcher

Frederic Myers Revd Frederic Myers (20 September 1811, Blackheath, London – 20 July 1851, Clifton, Cumberland) was a Church of England clergyman and author. He was the son of Thomas Myers (1774–1834), mathematician and geographer, and his wife, Anna Maria ...

. Its mirror is the

hypnagogic Hypnagogia is the experience of the transitional state from wakefulness to sleep: the ''hypnagogic'' state of consciousness, during the Sleep onset, onset of sleep. Its opposite state is described as the transitional state from sleep into wakeful ...

state at sleep onset; though often conflated, the two states are not identical and have a different phenomenological character. Hypnopompic and hypnagogic hallucinations are frequently accompanied by

sleep paralysis Sleep paralysis is a state, during waking up or falling asleep, in which one is conscious but is completely paralyzed. During an episode, one may hallucinate (hear, feel, or see things that are not there), which often results in fear. Episodes ...

, which is a state wherein one is consciously aware of one's surroundings but unable to move or speak.

Hallucinations

Hallucination A hallucination is a perception in the absence of an external stimulus that has the qualities of a real perception. Hallucinations are vivid, substantial, and are perceived to be located in external objective space. Hallucination is a combinatio ...

s are commonly understood as "sensory perceptions that occur in the absence of an objective stimulus". As this definition implies, though, like dreams, most hallucinations are visual, they can encompass a broader range of sensory experience. Auditory hallucinations are thus also common: "patients can hear simple sounds, structured melodies or complete sentences". Slightly less common but not unheard of are " somesthetic" hallucinations involving the sense of touch and location, with such experiences ranging from tactile sensations to full-blown " cenesthopathic" or "out-of-body experiences", which involve sudden changes in the perception of the body’s location, or even a sense of movement of the entire body. Finally, a unique characteristic of hypnopompic hallucinations is that as opposed to dreams, wherein they rarely understand that they are asleep, here sleepers do indeed have "the clear subjective awareness of being awake" yet are frequently mentally and physically trapped in the experience.

Neurobiology

The objective difference between the subjective experiences of dreams and hypnopompic hallucinations emerges from a close look at the sleep cycle and its attendant brain activity: there are essentially two types of sleep, R.E.M. sleep, which is indeed categorized by "rapid eye movement" and N.R.E.M., which stands for "Non-Rapid Eye Movement". In R.E.M. sleep, brains are extremely active. In particular, during this stage, both the brain-stem, which is the home of the most fundamental physical drives, and the parts of the cortex related to the most complex logical-cognitive functions experience highly intense electrical activity. Thus, R.E.M. is where the majority of dreaming occurs - it has been all but confirmed at this point that

dream A dream is a succession of images, ideas, emotions, and sensations that usually occur involuntarily in the mind during certain stages of sleep. Humans spend about two hours dreaming per night, and each dream lasts around 5 to 20 minutes, althou ...

s originate in the brain-stem, a spark from there driving the more logical mind to contemplate and consolidate, through dreaming, memories that relate to fulfilling fundamental drives. Conversely, there is almost no electrical activity during N.R.E.M. sleep. N.R.E.M. is what is referred to as "

deep sleep Slow-wave sleep (SWS), often referred to as deep sleep, consists of stage three of non-rapid eye movement sleep. It usually lasts between 70 and 90 minutes and takes place during the first hours of the night. Initially, SWS consisted of both St ...

", which is characterized by the complete quieting of the mind, to include dreamlessness, and by muscle "

atonia This glossary of medical terms is a list of definitions about medicine, its sub-disciplines, and related fields. A * Aarskog–Scott syndrome – (AAS) A rare, inherited (X-linked) disease characterized by short stature, facial abnormalities ...

", which is to say paralysis, a complete motor disconnect. A last critical point in this regard is that R.E.M. sleep cycles are book-ended by N.R.E.M. stages. It is precisely at this last point, though, that a quirk in brain chemistry, can cause hypnopompic hallucinations: occasionally during deep N.R.E.M., "transient patterns of neural activation in brainstem structures esemblingmicro-wake "fragments" can occur". These have a two-fold effect: first, just as in R.E.M. sleep, these brain-stem fragments essentially activate the dream mechanism. Second, they catalyze a near-waking state. However, this is often not powerful enough to jar a person completely out of deep sleep, and so only the mind fully awakens, leaving the body trapped in the atonia of deep sleep. Another reason why hypnopompic hallucinations are often such horrible experiences is that micro-wake fragments appear to be related to

serotonin Serotonin () or 5-hydroxytryptamine (5-HT) is a monoamine neurotransmitter. Its biological function is complex and multifaceted, modulating mood, cognition, reward, learning, memory, and numerous physiological processes such as vomiting and vas ...

and

dopamine Dopamine (DA, a contraction of 3,4-dihydroxyphenethylamine) is a neuromodulatory molecule that plays several important roles in cells. It is an organic compound, organic chemical of the catecholamine and phenethylamine families. Dopamine const ...

deficits—these deficits predispose a person to negative mental states, which likely causes the hallucinations to resemble bad dreams.

Cultural manifestations

These mental experiences are indeed often deeply damaging: across cultures, the experience of hypnopompic hallucinations are strongly related to "visitations of spirits, demons or other grotesque creatures belonging to traditional folklore". Thus, in the

Anglosphere The Anglosphere is a group of English-speaking world, English-speaking nations that share historical and cultural ties with England, and which today maintain close political, diplomatic and military co-operation. While the nations included in d ...

, hypnopompic experiences often entail the sense that an "

Old Hag Sleep paralysis is a state, during waking up or falling asleep, in which one is conscious but is completely paralyzed. During an episode, one may hallucinate (hear, feel, or see things that are not there), which often results in fear. Episodes ...

" or some similar "nocturnal spirit" is sitting on the sleeper’s chest, inducing both paralysis and an increasing, suffocating inability to move. Anthropologists have discovered references dating back to the High Middle ages of similar figures in Anglo-Saxon and Anglo-Norman traditions, most prominently the "'' mæra",'' the source of the word "nightmare", and which appears to have roots in ancient Germanic superstitions. Similarly, subjects belonging to Yoruban-African diasporas report feeling as though they are being "ridden" by the evil manifestations of their versions of the African pantheon (ridden is the vernacular for possession by the gods, who are often referred to as "divine horsemen"). Some members of the Yoruba diaspora appear to conflate the cultural interpretation of the experience, referring to "being ridden by the witch". Japanese interpretations of the experience are often grouped under the heading of ''kanashibari,'' a term which literally means "bound in gold or metal" and derives from the name of an esoteric Buddhist technique for paralyzing enemies.

Future research horizons

Owing to similarities between hypnagogic hallucinations and those experienced by people with

dementia Dementia is a disorder which manifests as a set of related symptoms, which usually surfaces when the brain is damaged by injury or disease. The symptoms involve progressive impairments in memory, thinking, and behavior, which negatively affe ...

Parkinson’s Parkinson's disease (PD), or simply Parkinson's, is a long-term degenerative disorder of the central nervous system that mainly affects the motor system. The symptoms usually emerge slowly, and as the disease worsens, non-motor symptoms become ...

and

schizophrenia Schizophrenia is a mental disorder characterized by continuous or relapsing episodes of psychosis. Major symptoms include hallucinations (typically hearing voices), delusions, and disorganized thinking. Other symptoms include social withdra ...

, significant progress is being made on understanding the neurobiological basis of this experience. Researchers have identified "a common neurofunctional substrate

hich Ij ( fa, ايج, also Romanized as Īj; also known as Hich and Īch) is a village in Golabar Rural District, in the Central District of Ijrud County, Zanjan Province, Iran Iran, officially the Islamic Republic of Iran, and also ...

points to a shared pattern of brain activation" underlying elements of schizophrenic delusions and these near-waking hallucinations: "with regional grey matter blood flow values being maximally increased in right parietal-occipital regions" during hypnagogic hallucinations and many schizoid episodes. Thus, such painful near-waking experiences could be rendered obsolete.

Notes

References