A psychedelic experience is an experience characterized by the perception of discovering previously unknown aspects of one's mind, or by the sense of creative exuberance of the mind when freed from its everyday conditioning and limitations.
Psychedelic experiences are comprised of an array of states including changes of perception such as internal and external hallucinations, synesthesia, altered states of awareness or focused consciousness, variation in thought patterns, trance or hypnotic states, mystical states, and other cognitive alterations. These processes can lead some people to experience changes in mental operation defining their self-identity (whether in momentary acuity or chronic development) different enough from their previous normal state that it can produce feelings of newly formed understanding such as mystical revelation, spiritual awakening, and/or confusion, and psychosis.
Psychedelic states may be elicited by various techniques, such as meditation, sensory stimulation or deprivation, and most commonly by the use of psychedelic substances. When these psychoactive substances are used for religious, shamanic, or spiritual purposes, they are termed entheogens.
"Reducing valve" theory
In his 1954 essay The Doors of Perception, author and psychonaut Aldous Huxley evoked the idea of the brain as a "mental reducing valve" to account for the phenomenology of the psychedelic experience.
According to Huxley, the primary function of the central nervous system is to filter out the majority of the sensory information that is available to be perceived; the brain filters those perceptions which are useful for survival. Society aids in this filtering by creating a symbolic system which structures our reality and which reduces our awareness. Psychedelics exert their characteristic effects by reducing the strength of the brain's reducing valve, which allows for a broader spectrum of one's overall experience to enter into conscious experience. According to this theory, a person undergoing a psychedelic experience temporarily possesses a "higher" level of conscious awareness.
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