Hypnogogia, also spelled Hypnagogia, is the name of an experience a person can go through when falling asleep. When in a hypnogogic state a person can have lifelike auditory, visual, or tactile hallucinations (known as hypnogogic hallucinations), perhaps even accompanied by full body paralysis. The invididual is aware that these are hallucinations; the frightening part, in many cases, is the inability to react to them, even being unable make a sound. In other cases one may enjoy truly vivid imaginations. The term was coined by the 19th century French psychologist Alfred Maury.

It is not an uncommon occurrence with 30 to 40 percent of people experiencing it at least once in their lives. However, it can be a sign of other problems such as narcolepsy or temporal lobe epilepsy.

It is thought to happen when a person enters REM (rapid eye movement) sleep too quickly. During REM the brain blocks the signals that allow the limbs to move to ensure that we do not act out our dreams. However, when experiencing hypnogogia, the individual is still conscious of their surroundings, effectively dreaming while still awake. This fact enabled lucid dreamers to enter the dream consciously directly from waking state (a Wake Induced Lucid Dream technique).

One method of getting out of this state is to stimulate a sensory nerve. Depending on the level of paralysis this can prove to be difficult. However, the eyes are still able to move and simply rolling them around can help. One suggestion is to blink rapidly and then attempt to move the facial muscles.

A disrupted sleep pattern or sleep deprivation is thought to be a primary cause of hypnogogia.

A similar phenomenon that occurs when awakening is hypnopompia.

See also

• Lucid dreaming
• Sleep disorder
• Sleep paralysis

Sleep may be divided into a third state, in addition to REM sleep and non-REM, slow wave, sleep. This is hypnagogia, the onset time between waking and stage 1 sleep, and it cannot be accurately categorized as waking or sleeping. Physiologically, the decay of alpha EEG activity and the cessation of eye movement characterize this period. (Hobson, Rowley, and Stickgold, 1998) There is a symmetrical state that defines the period between sleep and awakening, known as hypnapompia. These two states are similar and since little research has been done on hypnapompic sleep, it will not be further mentioned here.

The dream content of sleep onset differs from REM dreaming in several ways. Hypnagogia has been correlated with a number of anomalous processes including out of body experiences, psychokinesis, telepathy, and sleep paralysis, processes which cannot be explained in terms of known biological or physical mechanisms. (Sherwood, 2002) Researchers hope to better understand dream mechanisms and function by understanding the differences and similarities between dream content in the various stages of sleep.

Studies in which subjects are awoken between 15 seconds to five minutes after eyeball quiescence report that as sleepiness increases the total dream content recalled shortens and the frequency of normal waking thoughts declines. These declines are accompanied by an increase in unusual thoughts and formal dream features, composed of hallucinations, fictive movement, bizarreness, and narrative plot. Unusual thoughts and formal dream features are most pronounced during REM sleep. (Hobson, Rowley, and Stickgold, 1998)

As sleep onset progresses, awareness of the environment declines, as does reality testing. This term identifies the ability to recognize that the thoughts one are having are fictitious and impossible under realistic conditions. This includes the identification of events that were perceived to have occurred in the past as part of the dream, but in reality never occurred. It should be noted that although reality testing decreases with time in the hypnagogic state, during REM this ability is substantially more deficient.

Visual imagery dominates the hypnagogic state, similar to REM. Typically, representations in hypnagogia are more accurate than in REM sleep, although in both, the images are still represented abstractly with non-essential details removed. (Maguire, Malia, O’Conner, Roddenberry, and Stickgold, 2000) People most often visualize formless images (clouds, waves, etc.), geometric designs, faces, figures, animals, nature scenes, print writing, and tripping/falling sequences. The last of these are often associated with bodily jerks, called sleep starts. Occasionally, images occur solely in black and white. (Sherwood, 2002) As sleep onset progressives, image quality, vividness, luminosity, and intensity of color all tend to increase. (Nielson, 1992) Images can appear very small, micropsias, or conversely very large, megalopsias. Polyopsias are recurrent dream images. (Sherwood 2002)

Sound plays a secondary role in hypnagogia. The most common phenomena include crashing noises, one’s name being called, a doorbell ringing, references to spoken conversations, music, explosions, footsteps, and scratching. People sometimes perceive the smell of cigars, roses, burning, and other olfactory phenomena along with tactile, thermal, and gustatory sensations. In addition to these primary sensations, the content of sleep onset dreams has often been found to be symbolic (Mavromatis, 1987)

Based upon the relative percentages of dream features reported, researchers have inferred the relative order of appearance of dream visualizations from first to last: generic imagery, objects, faces, landscapes, complex episodes, mini-plays. (McKellar, 1989) A similar study has been done for the percentages of dream features and the subsequent order is as follows: visual imagery, representation of self, fictive motion and plot, bizarreness, audition and emotion, and somatosensory sensation. Such a progression indicates that bottom-up processes play a primary role in dream construction because visual imagery and visual detail precede the construction of plot. Top-down cognitive processes would predict a reverse order, and this factored heavily into the establishment of the activation-synthesis hypothesis. (Hobson and McCarley, 1977)

In addition to finding hypnagogic dream formation to be primarily a bottom-up process, researchers have concluded that implicit memory more heavily mediates the process than declarative memory. This claim is founded upon an experiment involving patients having bilateral hippocampal lesions, similar to those of the patient H.M. These amnesic patients were prompted to play several hours of Tetris daily. They subsequently visualized Tetris imagery during sleep onset, despite having no ability to explicitly recall playing the game.

The reported images originated form recent experiences, and thus one might assume involvement of hippocampal declarative memory. As stated above, this seems not to be the case. If image construction merely represented a reactivation of recent memories, the Tetris images should have been most common on the first night. Instead, ninety percent of the visualizations took place on the second night, indicating that dream manifestation is more complex than simple replay of recent experience.

A lack of hippocampal declarative memory involvement could account for a number of formal dream features. Without the mediation of the temporal and spatial associations of the hippocampus, the mind is free to produce content with novel connections, leading to bizarreness and discontinuity. Concomitant with these assertions is the finding that none of the hypnagogic dreams of either the amnesics or the normal controls contained episodic memories typically associated with declarative memory. For example, no one remembered sitting in their room playing Tetris or being at their computer. (Maguire, Malia, O’Conner, Roddenberry, and Stickgold, 2000)

Declarative memory processes would be even further weakened during REM sleep because not only is the hippocampus blocked, but the weak associations in the cortical memory systems are more strongly accessed than when one is awake. (Hobson, Stickgold, Scott, and Rittenhouse, 1999)

The above claims dovetail with another finding as follows. Although hypnagogic dreams can exhibit all the features of REM dreams as described earlier, only three percent of such dreams exhibit all the major features (hallucinations, representation of self, narrative plot, and bizarreness) characterizing REM sleep. Thus one may conceptualize hypnagogic imagery as a “micro-dream” in which the declarative memory system is gradually shut off, allowing for the full range of associations present in REM sleep. (Hobson, Rowley, and Stickgold, 1998) Additionally, the decline in reality testing, awareness of surroundings, and detailed accuracy of images adds further credence to this theory.

This decline in hippocampal processes may be used to account for the correlation between the hypnagogic state and anomalous processes. These singular experiences encompass extrasensory perception (ESP), communication with the dead, visions of past lives, out of body experiences, telepathy, psychokinesis, near death experiences, and encounters with extraterrestrials. Such experiences include a number of phenomena associated with the hypnagogic state such as sensations of floating or sinking, seeing lights, images, figures, landscapes, hearing noises, conversations, ones name being called, and sensations of being touched. Sleep onset may contain the optimal level of declarative memory blocking such that these experiences are created in the form of a dream, but nonetheless seem to be taking place while one is awake. Hypnagogia occasionally is also accompanied by momentary sleep paralysis, which contributes to the attribution of sleep onset dreams to anomalous processes. (Sherwood, 2002)

What is the function of the hypnagogic state? Scientist Robert Stickgold and colleagues have theorized that sleep onset dreams serve to alter the strengths or structures of associations in novel ways that cannot be achieved during waking hours because of the hippocampal declarative memory occluding the necessary pathways. Relatively predictable associations are forged during hypnagogia. Less predictable, frequently useless, but more exotic associations are modified during REM sleep. Regardless of the verity of this theory, the questions of how dream material is selected and incorporated, as well as what purpose the process serves, remains largely unresolved. (Maguire, Malia, O’Conner, Roddenberry, and Stickgold, 2000)

Bibliography: 1. Hobson, A.H., McCarley, R.W. (1977) The brain as a dream-state generator: An actiavation-synthesis hypothesis of the dream process, American Journal of Psychiatry vol. 134 pp 1335-1348 2. Hobson, A.H., Rowley, J.T., Stickgold, R. (1998) Eyelid Movements and Mental Activity at Sleep Onset, Conciousness and Cognition vol.7 pp 67-84 3. Hobson, A.H., Rittenhouse, C., Stickgold, R., and Scott, L. (1999) Cognitive Neuroscience vol. 11 pp 182 4. Maguire, D., Malia, A., O’Conner, M., Roddenberry, D., Stickgold, R. (2000) Replaying the Game: Hypnagogic Images in Normals and Amnesics, Science vol. 290 pp 350-353 5. Mavromatis, A. (1983) Hypnagogia: The nature and the function of the hypnagogic state, unpublished doctoral dissertation, Brunel University, England 6. McKellar, P. (1989) Abnormal Psychology: Its experience and behavior (London, Routledge) 7. Nielson, T.A. (1992) A self-observational study of spontaneous hypnagogic imagery using the upright napping procedure, Imagination, Cognition. And Personality vol. 11 pp 353-366 8. Sherwood, S.J. (2002) Relationship between the hypnagogic/hypnapompic states and reports of anomalous experiences – sleep, The Journal of Parapsychology vol. 70 pp 231-246