[Paleopsych] NYT: This Is Your Brain Under Hypnosis
checker at panix.com
Wed Nov 30 23:24:33 UTC 2005
This Is Your Brain Under Hypnosis
[This is quite an important article, not so much what is says about hypnosis
particularly, but about top-down processing, that what you think and how you
categorize the world shapes what you see. If this can be extended to several
top-down processes, we can better appreciate why so readily ignore
disconcordant information and arguments from bearers of bad news and Premise
By SANDRA BLAKESLEE
Hypnosis, with its long and checkered history in medicine and
entertainment, is receiving some new respect from neuroscientists.
Recent brain studies of people who are susceptible to suggestion
indicate that when they act on the suggestions their brains show
profound changes in how they process information. The suggestions,
researchers report, literally change what people see, hear, feel and
believe to be true.
The new experiments, which used brain imaging, found that people who
were hypnotized "saw" colors where there were none. Others lost the
ability to make simple decisions. Some people looked at common English
words and thought that they were gibberish.
"The idea that perceptions can be manipulated by expectations" is
fundamental to the study of cognition, said Michael I. Posner, an
emeritus professor of neuroscience at the University of Oregon and
expert on attention. "But now we're really getting at the mechanisms."
Even with little understanding of how it works, hypnosis has been used
in medicine since the 1950's to treat pain and, more recently, as a
treatment for anxiety, depression, trauma, irritable bowel syndrome
and eating disorders.
There is, however, still disagreement about what exactly the hypnotic
state is or, indeed, whether it is anything more than an effort to
please the hypnotist or a natural form of extreme concentration where
people become oblivious to their surroundings while lost in thought.
Hypnosis had a false start in the 18th century when a German
physician, Dr. Franz Mesmer, devised a miraculous cure for people
suffering all manner of unexplained medical problems. Amid dim lights
and ethereal music played on a glass harmonica, he infused them with
an invisible "magnetic fluid" that only he was able to muster. Thus
mesmerized, clients were cured.
Although Dr. Mesmer was eventually discredited, he was the first
person to show that the mind could be manipulated by suggestion to
affect the body, historians say. This central finding was resurrected
by Dr. James Braid, an English ophthalmologist who in 1842 coined the
word hypnosis after the Greek word for sleep.
Braid reportedly put people into trances by staring at them intently,
but he did not have a clue as to how it worked. In this vacuum,
hypnosis was adopted by spiritualists and stage magicians who used
dangling gold watches to induce hypnotic states in volunteers from the
audience, and make them dance, sing or pretend to be someone else,
only to awaken at a hand clap and laughter from the crowd.
In medical hands, hypnosis was no laughing matter. In the 19th
century, physicians in India successfully used hypnosis as anesthesia,
even for limb amputations. The practice fell from favor only when
ether was discovered.
Now, Dr. Posner and others said, new research on hypnosis and
suggestion is providing a new view into the cogs and wheels of normal
One area that it may have illuminated is the processing of sensory
data. Information from the eyes, ears and body is carried to primary
sensory regions in the brain. From there, it is carried to so-called
higher regions where interpretation occurs.
For example, photons bouncing off a flower first reach the eye, where
they are turned into a pattern that is sent to the primary visual
cortex. There, the rough shape of the flower is recognized. The
pattern is next sent to a higher - in terms of function - region,
where color is recognized, and then to a higher region, where the
flower's identity is encoded along with other knowledge about the
The same processing stream, from lower to higher regions, exists for
sounds, touch and other sensory information. Researchers call this
direction of flow feedforward. As raw sensory data is carried to a
part of the brain that creates a comprehensible, conscious impression,
the data is moving from bottom to top.
Bundles of nerve cells dedicated to each sense carry sensory
information. The surprise is the amount of traffic the other way, from
top to bottom, called feedback. There are 10 times as many nerve
fibers carrying information down as there are carrying it up.
These extensive feedback circuits mean that consciousness, what people
see, hear, feel and believe, is based on what neuroscientists call
"top down processing." What you see is not always what you get,
because what you see depends on a framework built by experience that
stands ready to interpret the raw information - as a flower or a
hammer or a face.
The top-down structure explains a lot. If the construction of reality
has so much top-down processing, that would make sense of the powers
of placebos (a sugar pill will make you feel better), nocebos (a witch
doctor will make you ill), talk therapy and meditation. If the top is
convinced, the bottom level of data will be overruled.
This brain structure would also explain hypnosis, which is all about
creating such formidable top-down processing that suggestions overcome
According to decades of research, 10 to 15 percent of adults are
highly hypnotizable, said Dr. David Spiegel, a psychiatrist at
Stanford who studies the clinical uses of hypnosis. Up to age 12,
however, before top-down circuits mature, 80 to 85 percent of children
are highly hypnotizable.
One adult in five is flat out resistant to hypnosis, Dr. Spiegel said.
The rest are in between, he said.
In some of the most recent work, Dr. Amir Raz, an assistant professor
of clinical neuroscience at Columbia, chose to study highly
hypnotizable people with the help of a standard psychological test
that probes conflict in the brain. As a professional magician who
became a scientist to understand better the slippery nature of
attention, Dr. Raz said that he "wanted to do something really
impressive" that other neuroscientists could not ignore.
The probe, called the Stroop test, presents words in block letters in
the colors red, blue, green and yellow. The subject has to press a
button identifying the color of the letters. The difficulty is that
sometimes the word RED is colored green. Or the word YELLOW is colored
For people who are literate, reading is so deeply ingrained that it
invariably takes them a little bit longer to override the automatic
reading of a word like RED and press a button that says green. This is
called the Stroop effect.
Sixteen people, half highly hypnotizable and half resistant, went into
Dr. Raz's lab after having been covertly tested for hypnotizability.
The purpose of the study, they were told, was to investigate the
effects of suggestion on cognitive performance. After each person
underwent a hypnotic induction, Dr. Raz said:
"Very soon you will be playing a computer game inside a brain scanner.
Every time you hear my voice over the intercom, you will immediately
realize that meaningless symbols are going to appear in the middle of
the screen. They will feel like characters in a foreign language that
you do not know, and you will not attempt to attribute any meaning to
"This gibberish will be printed in one of four ink colors: red, blue,
green or yellow. Although you will only attend to color, you will see
all the scrambled signs crisply. Your job is to quickly and accurately
depress the key that corresponds to the color shown. You can play this
game effortlessly. As soon as the scanning noise stops, you will relax
back to your regular reading self."
Dr. Raz then ended the hypnosis session, leaving each person with what
is called a posthypnotic suggestion, an instruction to carry out an
action while not hypnotized.
Days later, the subjects entered the brain scanner.
In highly hypnotizables, when Dr. Raz's instructions came over the
intercom, the Stroop effect was obliterated, he said. The subjects saw
English words as gibberish and named colors instantly. But for those
who were resistant to hypnosis, the Stroop effect prevailed, rendering
them significantly slower in naming the colors.
When the brain scans of the two groups were compared, a distinct
pattern appeared. Among the hypnotizables, Dr. Raz said, the visual
area of the brain that usually decodes written words did not become
active. And a region in the front of the brain that usually detects
conflict was similarly dampened.
Top-down processes overrode brain circuits devoted to reading and
detecting conflict, Dr. Raz said, although he did not know exactly how
that happened. Those results appeared in July in The Proceedings of
the National Academy of Sciences.
A number of other recent studies of brain imaging point to similar
top-down brain mechanisms under the influence of suggestion. Highly
hypnotizable people were able to "drain" color from a colorful
abstract drawing or "add" color to the same drawing rendered in gray
tones. In each case, the parts of their brains involved in color
perception were differently activated.
Brain scans show that the control mechanisms for deciding what to do
in the face of conflict become uncoupled when people are hypnotized.
Top-down processes override sensory, or bottom-up information, said
Dr. Stephen M. Kosslyn, a neuroscientist at Harvard. People think that
sights, sounds and touch from the outside world constitute reality.
But the brain constructs what it perceives based on past experience,
Dr. Kosslyn said.
Most of the time bottom-up information matches top-down expectation,
Dr. Spiegel said. But hypnosis is interesting because it creates a
mismatch. "We imagine something different, so it is different," he
More information about the paleopsych