Psilocybin's effects on cognition:
Recent research and its implications for enhancing creativity
Matthew J. Baggott
Research Associate, Drug Dependence Research Center
University of California, San Francisco
mbagg@itsa.ucsf.edu
http://itsa.ucsf.edu/~ddrc
For an updated list of psilocybin studies,
click here
For Rick Doblin's long-term followup studies to psilocybin research
originally conducted or supervised by Timothy Leary at Harvard from 1960-1963, see the
Good Friday experiment follow-up,
investigating the use of psilocybin in catalyzing mystical experiences, and the
Concord Prison experiment follow-up,
investigating the use of psilocybin in promoting behavior change and reduced
recidivism.
Discussion of the article: Spitzer M, Thimm M, Hermle L, Holzmann P,
Kovar KA, Heimann H, Gouzoulis-Mayfrank E, Kischka U, Schneider F (1996);
Increased activation of indirect semantic associations under psilocybin.
Biol Psychiatry 39:1055-1057.
Spitzer and his colleagues have come closer to understanding the effects
of psychedelics. As they point out in the conclusion of their paper, they
have succeeded in using the results of a simple task to theorize
connections between the subjective reports of psychedelic users,
objective measures of psilocybin's effects, and underlying brain
physiology. In the process they raised a number of productive leads for
further research.
The "first wave" of psychedelic research in the 1960s saw many
attempts to understand the mechanisms and effects of psychedelics. Looking
back on this past research, one gets the idea that psychedelic substances
were perhaps too complex for the scientific tools of the time. The
current wave of psychedelic research therefore holds much promise. Since
the 1960's, we have gained many sophisticated research tools. These tools
include neuropsychological tests-simple, repetitive, game-like
tasks-which can give valuable insight into how psychedelics affect the
mind. Manfred Spitzer, M.D., Ph.D., and his colleagues (1996) recently
published a fascinating report on the effects of psilocybin on one such
neuropsychological test.
Spitzer's group orally administered 0.2 mg/kg body weight of psilocybin to
eight male volunteers in a double-blind, placebo-controlled experiment.
They then studied the effects of psilocybin in a word-recognition task. In
this task, subjects identify whether a string of characters is a word or
not. Past research has found that subjects can identify a word faster if
the previous string of characters is a closely related word. For example,
subjects can recognize the word "black" more quickly if it has
been immediately preceeded by the word "white." This effect is
known as semantic priming. In normal subjects, semantic priming occurs
only with closely related words. However, indirectly related words
("sweet" and "lemon," for example) produce semantic
priming in thought-disordered schizophrenic subjects (Spitzer et al 1993a,
1993b).
Semantic priming
The researchers found that psilocybin slowed the subjects' reaction times
while at the same time producing a semantic priming effect for indirectly
related words ("sweet" and "lemon"), similar to that
seen in the schizophrenia research. The finding that psilocybin slowed
reaction times was not unexpected; past research with psychedelics has
found the same effect. However, the finding that psilocybin produced
indirect semantic priming is more interesting. In their discussion, the
researchers point out that their findings are relevant to claims that
psychedelics "enhance creativity" or "broaden
consciousness":
Although most objective measures have failed to support these
claims, our data suggest that the [hallucinogenic] agent in fact leads
to an increased availability of remote associations and thereby may
bring cognitive contents to mind that under normal circumstances
remain nonactivated; however, the generally decreased psychological
performance under hallucinogenic agents suggest that the increased
indirect priming effect is due to a decreased capacity to use
contextual information for the focusing of semantic processing.
Hence, subjectively experienced increases in creativity as well as
the broadening of consciousness have been found to parallel
decreases in objective performance measures (p. 1056-1057).
Thus, the researchers suggest that psychedelics may in fact "broaden
consciousness" by making remote mental associations more available.
However, this involves a trade-off. Although remote mental associations
are more available, subjects are less able to focus, which slows their
reaction times.
Semantic neural networks
The researchers interpret their findings using a model which states that
the brain contains semantic neural networks which can become activated by
semantic information. The spread of this activation through the networks
determines the amount of semantic priming that occurs in the word-recognition
task. Activation spreads further and faster in thought-disordered
schizophrenics and psilocybin users than in normal volunteers.
One explanation for this unusual amount of activation is decreased
efficiency in the cortex where semantic information is processed
(Servan-Schreiber et al 1990, Cohen and Servan-Schreiber 1992, 1993).
There is evidence that this inefficient processing is related to the
decreased dopaminergic modulation. In support of this theory, the
researchers have found that L-dopa, a precursor to dopamine, reduces the
spread of activation and therefore reduces indirect semantic priming
(Kischka et al 1995). In the context of this theory, psilocybin (which
acts on the serotonin system) can be seen as increasing activation of
semantic networks. Essentially, dopamine seems to have a focusing effect
on activation of semantic networks while psilocybin has a defocusing
effect.
Word-recognition task
The word-recognition task used by Spitzer's group is particularly
interesting for a number of reasons. First, it allows researchers to test
automatic rather than voluntary access to memory. Even when subjects
cannot consciously recall previously viewed words (whether because of a
drug or neurological disorder), the word-recognition task can demonstrate
whether subjects can still automatically access that memory. In addition,
the task allows researchers to see how the focus of subjects' mental
associations is changed by different pharmacological or psychological
states. This aspect seems potentially promising for distinguishing between
different types of memories. For example, in some situations, emotional
words ("happy" and "sad") might be activated to a
greater extent than words with little emotional content ("black"
and "white").
Spitzer and his colleagues have come closer to understanding the effects
of psychedelics. As they point out in the conclusion of their paper, they
have succeeded in using the results of a simple task to theorize
connections between the subjective reports of psychedelic users, objective
measures of psilocybin's effects, and underlying brain physiology. In the
process they raised a number of productive leads for further research.
References
- Cohen JD, Servan-Schreiber D (1992); Context, cortex and dopamine: A
connectionist approach to behavior and biology in schizophrenia. Psychol
Rev 12:45-77.
- Cohen JD, Servan-Schreiber D (1993); A theory of dopamine function and
its role in cognitive deficits in schizophrenia.
Schizoph Bull 19:85-104.
- Kischka U, Kammer T, Weisbrod M, Maier S, Thimm M, Spitzer M (1995);
Dopaminergic modulation of semantic network activation (in submission).
Servan-Schreiber D, Printz H, Cohen JD (1990); A network model of
catcholamine effects: Gain, signal-to-noise ratio, and behavior. Science
249:892-895.
- Spitzer M, Braun U, Maier S, Hermle L, Maher BA (1993a); Indirect
semantic priming in schizophrenic patients. Schizoph Res 11:71-80.
- Spitzer M, Braun U, Hermle L, Maier S (1993b); Associative semantic
network dysfunction in thought-disordered schizophrenic patients: Direct
evidence from indirect semantic priming.
Biol Psychiatry 34:864-877.
- Spitzer M, Thimm M, Hermle L, Holzmann P, Kovar KA, Heimann H,
Gouzoulis-Mayfrank E, Kischka U, Schneider F (1996); Increased activation
of indirect semantic associations under psilocybin.
Biol Psychiatry 39:1055-1057.
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