- Hypnosis is more than just a party trick, it measurably
changes how the brain works, says a UK researcher.
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- Hypnosis significantly affects the activity in a part
of the brain responsible for detecting and responding to errors, says John
Gruzelier, a psychologist at Imperial College in London. Using functional
brain imaging, he also found that hypnosis affects an area that controls
higher level executive functions.
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- "This explains why, under hypnosis, people can do
outrageous things that ordinarily they wouldn't dream of doing," says
Gruzelier, who presented his study at the British Association for the
Advancement
of Science Festival in Exeter, UK.
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- The finding is one of the first to indicate a biological
mechanism underpinning the experience of hypnosis. Gruzelier hopes it will
also benefit emerging research showing, for example, that hypnosis can
help cancer patients deal with painful treatments.
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- Highly susceptible
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- Gruzelier and his colleagues studied brain activity using
an fMRI while subjects completed a standard cognitive exercise, called
the Stroop task.
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- The team screened subjects before the study and chose
12 that were highly susceptible to hypnosis and 12 with low susceptibility.
They all completed the task in the fMRI under normal conditions and then
again under hypnosis.
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- Throughout the study, both groups were consistent in
their task results, achieving similar scores regardless of their mental
state. During their first task session, before hypnosis, there were no
significant differences in brain activity between the groups.
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- But under hypnosis, Gruzelier found that the highly
susceptible
subjects showed significantly more brain activity in the anterior cingulate
gyrus than the weakly susceptible subjects. This area of the brain has
been shown to respond to errors and evaluate emotional outcomes.
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- The highly susceptible group also showed much greater
brain activity on the left side of the prefrontal cortex than the weakly
susceptible group. This is an area involved with higher level cognitive
processing and behaviour.
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- Stage hypnotists
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- Gruzelier concludes that, under hypnosis, these brain
areas are having to work much harder to achieve the same cognitive task
results. "This is confirming our model of hypnosis with very direct
evidence of brain function," he says.
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- Peter Naish, at the UK's Open University, says this moves
the understanding of hypnosis away from the popular misconceptions created
by showy stage hypnotists.
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- "We have a technique that has now moved towards
evidence-based treatments," he says. "Gruzelier's work is showing
for sure that the brain is doing quite different things under hypnosis
than in normal everyday existence."
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- Clinical trials of therapeutic hypnosis are starting
to confirm its potential benefits. Christina Liossi, a psychologist at
the University of Wales in Swansea, recently conducted a study of 80 cancer
patients aged 6 to 16.
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- She found that those under hypnosis experienced far less
pain during treatments than control children, who simply talked to the
researchers normally.
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