As reported in a previous article,
a number of fascinating studies recently have focused on the effects of the
drug psilocybin, a classic psychedelic drug. Scientists still do not have a
good understanding of the brain mechanisms by which psilocybin produces its
effects. A recent study
used brain scanning (specifically, functional magnetic resonance imaging) to
obtain a window into the brain of 30 volunteers injected with this drug in
order to understand what happens during the transition between normal waking
consciousness and the onset of drug effects (Carhart-Harris
et al., 2012). The researchers were surprised to discover that drug
effects were associated with decreases in
activity in a number of key brain areas, rather than the expected increase.
This finding has led to speculations
about the relationship between brain activity and mystical states experienced
under psychedelic drugs. However, the actual implications of the study’s
findings are far from clear.
In this study, participants received two brain scans each,
once after receiving a saline injection, and once after receiving a psilocybin
injection. The effects on brain activity were then compared. After receiving
psilocybin brain blood flow decreased, indicating reduced activity. In
particular, activity in areas regarded as important network hubs that maintain
the connectivity of the various areas of the brain showed the most consistent
deactivation. These areas are known as the medial prefrontal cortex (mPFC) and
the posterior cingulate cortex (PCC). (If you’re put off by neuroscience please
don’t quit reading just yet! I’ll try to keep the brain science as simple as
possible.) These two areas appear to play important roles in the regulation of
self-awareness as they are particularly activated when people are asked to
think about themselves for example (Wicker,
Ruby, Royet, & Fonlupt, 2003). The authors thought it was quite
interesting that these areas actually show much higher activity than other
parts of the brain under normal conditions, yet showed the greatest
deactivation under the drug. Additionally, the intensity of the alterations of
conscious experience reported by the volunteers was proportional to the
decrease in brain activity. That is, the more brain activity decreased, the
more vivid the “trip” experienced.
Why psilocybin might induce reductions in brain activity is
not known, but it is natural to speculate. The authors argued that the findings
are consistent with Aldous Huxley’s idea that normal consciousness acts like a
“reducing valve” that actually constrains how much information a person
normally takes in, so that one is not overwhelmed by chaotic stimuli.
Therefore, the apparent “mind-expanding” effect of psychedelic drugs is due to
a relaxation of this constraining effect. The reduced activity of the brains
connector hubs might permit an “unconstrained style of cognition” producing
psychedelic effects (Carhart-Harris, et al.,
2012).
In an article for Time
magazine, Carhart-Harris takes these speculations even
further. Under high doses of psilocybin many people experience a sense
of ego-transcendence in which the boundaries of the self appear to dissolve
resulting in a blissful state of oneness with the universe. As noted earlier,
areas of the brain associated with self-awareness, the mPFC and the PCC, showed
a marked reduction in activity under psilocybin. This could imply that
ego-transcendence might be facilitated by reduced activity in these brain
areas. This idea seems appealing when considering that contemplative traditions
aim to produce ego-transcendence by quietening the mind.
However, let’s not
jump to conclusions just yet. There is a potential problem with Carhart-Harris
et al.’s interpretation of their results that they appear to have overlooked. Previous
research has found that a number of areas of the brain, including the mPFC and
the PCC actually show heightened levels of activity when a person is simply at
rest and show decreased activity when
concentrating attention on various tasks unrelated to thinking about oneself (D'Argembeau et al., 2005; Wicker, et al., 2003).
So while it is true that these brain areas are important for self-awareness,
simple tasks such as looking out a window or thinking about another person can
reduce activity in these areas under normal circumstances. In the
Carhart-Harris et al. study brain activity under psilocybin was compared to
brain activity when simply resting. This is potentially a problem because
activity in the mPFC and PCC tends to be highest when at rest. Therefore,
reduced activity in these regions under psilocybin might simply be because
volunteers were paying attention to the unfolding hallucinatory experience as
opposed to thinking of nothing in particular. Future studies could test this by
using a comparison condition where participants were engaged in an attentional
task as opposed to simply resting. If there were noticeable differences in the
degree of deactivation in the key brain areas this might provide evidence that
these particular brain areas do play a special role in the psilocybin
experience.
In spite of these concerns, I do think the idea that
psilocybin permits an “unconstrained style of cognition” is an intriguing one.
As discussed in my previous article
there is a strong association between the personality trait absorption and the
degree to which a person experiences alterations in consciousness under
psilocybin (Studerus, Gamma, Kometer, &
Vollenweider, 2012). Absorption is associated with a tendency to have
unusual ideas and loose associations, suggesting that high absorption is
associated with a style of cognition that is much less constrained than that of
the average person. Additionally, one study of volunteers who had never taken
psychedelic drugs before found that volunteers who experienced a profound
mystical experience under psilocybin underwent a long-term increase in openness
to experience (MacLean, Johnson, &
Griffiths, 2011), a personality trait closely related to absorption.
This suggests that for some people, taking psilocybin could lead to a lasting
change in their cognitive style, perhaps related to the intensely
“unconstrained” style experienced under psilocybin.
The study of the effects of psilocybin on brain function is
in its infancy. More research into this area could lead to some intriguing
findings about the relationship between the brain and consciousness.
Further reading
Another critique of the Carhart-Harris et al. study can be
found here.
© Scott McGreal. Please do not reproduce without
permission. Brief excerpts may be quoted as long as a link to the original
article is provided.
This article also appears on Psychology Today on
my blog Unique - Like Everybody Else.
Other posts about
psychedelic drugs and/or spirituality
References
Carhart-Harris RL, Erritzoe D, Williams T, Stone JM, Reed LJ, Colasanti A, Tyacke RJ, Leech R, Malizia AL, Murphy K, Hobden P, Evans J, Feilding A, Wise RG, & Nutt DJ (2012). Neural correlates of the psychedelic state as determined by fMRI studies with psilocybin. Proceedings of the National Academy of Sciences of the United States of America, 109 (6), 2138-43 PMID: 22308440
MacLean, K., Johnson, M., & Griffiths, R. (2011). Mystical experiences occasioned by the hallucinogen psilocybin lead to increases in the personality domain of openness Journal of Psychopharmacology, 25 (11), 1453-1461 DOI: 10.1177/0269881111420188
Wicker, B., Ruby, P., Royet, J., & Fonlupt, P. (2003). A relation between rest and the self in the brain? Brain Research Reviews, 43 (2), 224-230 DOI: 10.1016/j.brainresrev.2003.08.003
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