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Science & Consciousness Review
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Psychedelics constitute a class of psychoactive drugs with unique effects on consciousness.
Psychedelic means “mind-manifesting” and refers to the ability of these drugs to illuminate
normally hidden aspects of mind or psyche. Native American shamans consumed psychedelic
plants such as the peyote cactus (contains mescaline), psilocybe “magic” mushrooms (contains
psilocybin), or the brew called ayahuasca (contains DMT and harmaline) in order to
communicate with God or the spirit realm.
The most potent psychedelic is the semi-synthetic ergot derivative lysergic acid diethylamide
(LSD), which has detectable effects at microscopic doses. This drug was discovered by the
Swiss chemist Albert Hoffman in 1943. While handling vials containing the chemical, he
accidentally absorbed some of it through his skin, and later experienced a strange state of
consciousness. Suspecting that LSD was the cause, Hoffman decided to test the drug on
himself, starting with what he thought would be a small and probably ineffective dose - only ¼
of a milligram. However, for LSD this is a rather large dose. Hoffman’s ensuing “trip” was
overwhelmingly intense and he assumed he was either dying or going insane (Hoffman, 1981).
Hoffman recovered and a period of scientific research on LSD began.
Researchers first thought LSD induced a “model psychosis” that might shed light on the nature
of schizophrenia. However, as the psychedelic experience or “trip” does not resemble
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endogenous psychoses, this interpretation was later discarded.
In the 1950s the therapeutic potential of LSD was investigated
under the assumption that LSD was a key that could unlock the
secrets of the unconscious mind. Thousands of people in the
U.S., including the actor Cary Grant, underwent “psycholytic” (“mind-loosening”) therapy
under LSD during the 1950s and early 1960s (Grinspoon & Bakalar, 1979). Other work
investigated the religious aspect of high-dose psychedelic experiences. In a 1961 experiment
known as the “Miracle of March Chapel,” Boston Divinity Students were given psilocybin or
placebo in a double-blind design; most subjects in the psilocybin group (and none in the
placebo group) reported profound religious experiences with lasting beneficial consequences
(Doblin, 1991). Scientific and clinical work with psychedelics was interrupted when the drugs
were outlawed in the U.S. in 1965 as a response to their growing non-medical use, but in
recent years, renewed scientific interest in consciousness has led to a small revival of
psychedelic drug research.
Unlike most drugs, psychedelics do not produce reliable, consistent effects across users, or
even in the same user at different times. The most positive accounts describe mystical
revelations such as gaining direct knowledge of God or an all-encompassing cosmic unity. More
commonly reported is a kaleidoscopic display of intensely colorful visions, ranging from
continuously unfolding abstract designs to fully formed images of animals, plants, landscapes
or more bizarre scenes. However, taking a psychedelic also entails the risk that the user may
spiral down into the black hole of a “bad trip,” an overwhelming state of terror and psychic
anguish that can be followed by lasting PTSD-type symptoms such as flashbacks. “Bad trips”
are the main hazard of psychedelic drug use, as the possibility of a lethal overdose is
vanishingly small.
Psychedelic drugs are not addictive. Even enthusiastic proponents
of psychedelics take them infrequently due to the intensity of the
“trip.” Animal research indicates that
Homo sapiens
is the only
species that will voluntarily take a psychedelic drug again after
having experienced the effects. Although laboratory animals such
as rats or monkeys will readily self-admininister most other
drugs
abused by humans, including cocaine, heroin, amphetamine,
nicotine and alcohol, they find psychedelic drugs highly aversive (Yokel, 1987).
The question of how these agents produce their striking alterations of consciousness has long
fascinated brain researchers. The first clue was that LSD, psilocybin, DMT, and many other
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psychedelics bear a close structural similarity to the neurotransmitter serotonin. Research in
the 1970s showed that LSD temporarily suppresses the firing of serotonin-releasing neurons of
the raphe nuclei (Rechs & Rosecrans, 1982), a part of the brainstem reticular activating
system. These neurons send axons into widespread regions of the cerebral cortex and limbic
system, where they release serotonin when active. Because the raphe nuclei also go silent
during REM sleep, the notion that the psychedelic state represents “dreaming while awake”
became the standard account. However, subsequent research contradicted this interpretation
by showing that LSD and other psychedelics act postsynaptically as agonists at 5-HT2
receptors (Jacobs, 1987), the most common serotonin receptors in the brain. The silencing of
the raphe nuclei was due to LSD’s agonist action at presynaptic
autoreceptors (inhibitory 5-HT1) on the serotonin-releasing cells.
Autoreceptors serve a negative feedback function such that the
neurotransmitter (in this case serotonin) inhibits its own release
when extracellular levels are too high. LSD thus acts like
serotonin both presynaptically and postsynaptically, inhibiting
serotonin release via inhibitory 5-HT1 autoreceptors while simultaneously activating excitatory
postsynaptic 5-HT2 receptors; only the latter action is relevant to the psychedelic state
(Feldman, Meyer & Quenzer, 1997). This interpretation was bolstered by the finding that
serotonin antagonists can block psychedelic effects. Recent PET scans of volunteers under the
influence of psilocybin showed hyperactivity of the frontal and occipital lobes,
especially in the
right hemisphere, presumably reflecting strong activation of excitatory 5-HT2 receptors in the
cortex (Vollenweider et al., 1997).
But how and why these brain changes translate into
psychedelic experiences are questions as difficult as the mind-body problem itself.
Research on the brain actions of psychedelic drugs has potential implications for theories of
consciousness and the brain correlates of mystical experiences. People who claim to have had
a mystical experience under the influence of a psychedelic give reports that are often similar to
the accounts of non-drug using religious mystics from the major religious traditions (Pahnke &
Richards, 1966). Themes such as the unity of all sentient beings, oneness with God and the
universe, and the illusory nature of human existence have been reported by figures as diverse
as Buddha, the Christian mystic Meister Eckhart, and psychologist turned sixties LSD guru
Timothy Leary. The psychedelic experience thus represents a unique intersection between
mind, matter, science and mysticism that still defies explanation.
Copyright © 2003, M. Lyvers
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Michael Lyvers
Associate Professor of Psychology
Bond University
Gold Coast Qld 4229 AUSTRALIA
e-mail: mlyvers@staff.bond.edu.au
References
Doblin, R. (1991). The Good Friday experiment – a twenty five year follow-up and methodological critique.
Journal of
Transpersonal Psychology, 23(1),
1-28.
Feldman, R.S., Meyer, J.S., & Quenzer, L.F. (1997).
Principles of neuropsychopharmacology
. Sunderland, MA: Sinauer.
Grinspoon, L., & Balakar, J.B. (1979).
Psychedelic drugs reconsidered
. New York: Basic Books.
Hoffman, A. (1981).
LSD, my problem child
. New York: McGraw-Hill.
Jacobs, B.L. (1987). How hallucinogenic drugs work.
American Scientist, 75
, 386-392.
Pahnke, W.N., & Richards, W.A. (1966). Implications of LSD and experimental mysticism.
Journal of Religion & Health,
5
, 175-208.
Rechs, R.H., & Rosecrans, J.A. (1982). Review of mechanisms of hallucinogenic drug action.
Neuroscience &
Biobehavioral Reviews, 6
, 481-482.
Vollenweider, F.X., Leenders, K.L., Scharfetter, C., Maguire, P., Stadelmann, O., & Angst, J. (1997). Positron emission
tomography and fluorodeoxyglucose studies of metabolic hyperfrontality and psychopathology in the psilocybin model
of psychosis.
Neuropsychopharmacology, 16
, 357.
Yokel, R.A. (1987). Intravenous self-administration: Response rates, the effect of pharmacological challenges and drug
preferences. In M.A. Bozarth (Ed.),
Methods of assessing the reinforcing properties of abused drugs
(pp. 1-34). New
York: Springer-Verlag.
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