Hi All.,

Here is an article to share on "Hypnosis, Memorory and the Brain


Mind Matters - October 7, 2008

Hypnosis, Memory and the Brain
A new study points to specific areas of the brain affected by hypnosis. The
technique could be a tool for exploring what happens in the brain when we
suddenly forget.
By Amanda J. Barnier, Rochelle E. Cox and Greg Savage


Hypnosis has long been considered a valuable technique for recreating and then
studying puzzling psychological phenomena. A classic example of this approach
uses a technique known as posthypnotic amnesia (PHA) to model memory disorders
such as functional amnesia, which involves a sudden memory loss typically due to
some sort of psychological trauma (rather than to brain damage or disease).
Hypnotists produce PHA by suggesting to a hypnotized person that after hypnosis
he will forget particular things until he receives a “cancellation,” such as
“Now you can remember everything.” PHA typically only happens when it is
specifically suggested and it is much more likely to occur in those with high
levels of hypnotic ability, or “high hypnotizable” people. Now a new study
shows that this hypnotic state actually influences brain activity associated
with memory.

High hypnotizable people with PHA typically show impaired explicit memory, or
difficulty consciously recalling events or material targeted by the suggestion,
and a dissociation between implicit and explicit memory, so that even though
they can’t recall the forgotten information it continues to influence their
behavior, thoughts and actions. The forgetting is reversible—when the
suggestion is cancelled, their memories come flooding back. These last two
features—the dissociation and reversibility—confirm that PHA is not the
result of poor encoding of the memories or of normal forgetting, because the
memories return as soon as PHA is cancelled. Rather, PHA reflects a temporary
inability to retrieve information that is safely stored in memory. That makes it
a useful tool for research.

Researchers have used PHA as a laboratory analogue of functional amnesia because
these conditions share several similar features. Case reports of functional
amnesia, for instance, describe men and women who, following a traumatic
experience such as a violent sexual assault or the death of a loved one, are
unable to remember part or all of their personal past. However, as in PHA, they
might still show “implicit” evidence of the forgotten events. For instance,
they might unconsciously dial the phone number of a family member whom they
can’t consciously recall. (In contrast, explicit memories are those we
consciously have access to, such as remembering a childhood birthday or what you
had for dinner last night.) And, as suddenly as they lost their memories, they
can just as suddenly recover them.

Forgetting in the Brain
But for the comparison between PHA and functional amnesia to be most meaningful,
we need to know that they share underlying processes. One way to test this is to
identify the brain activity patterns associated with PHA. In a groundbreaking
study published in Neuron, neuroscientist Avi Mendelsohn and colleagues at the
Weizmann Institute in Israel did just that using functional magnetic resonance
imaging (fMRI). They carefully selected 25 people to participate in their
experiment. Although all were susceptible to hypnosis, earlier testing had shown
that half could respond to a PHA suggestion (labelled “the PHA group”) and
half could not (the “non-PHA group”). In the Study session of their
experiment, participants watched a 45-minute movie. One week later, in the Test
session, participants returned to the laboratory and were hypnotized while they
lay within the fMRI scanner. During hypnosis, people in both the PHA and non-PHA
groups received a
suggestion to forget the movie until they heard a specific cancellation cue.

After hypnosis, participants’ memories were tested twice while the fMRI
scanner recorded their brain activity. For Test 1, they were asked 40 questions
about the content of the movie (for example, the actress knocked on her
neighbor’s door on the way home) and 20 questions about the context in which
they saw the movie (for instance, during the movie, the door to the study room
was closed). These questions required a “yes” or “no” response. For Test
2, participants were asked the same 60 recognition questions, but first they
heard the cue to cancel PHA. So Test 1 measured memory performance and brain
activity while the PHA suggestion was in effect and Test 2 measured memory
performance and brain activity after it was cancelled.

In Test 1 Mendelsohn and colleagues found that people in the PHA group (who
could experience PHA) forgot more details from the movie than people in the
non-PHA group (who could not experience PHA). But in Test 2, after the
suggestion was cancelled, this memory loss was reversed. People in the PHA group
correctly recognized just as many details from the movie as people in the
non-PHA group. Somewhat surprisingly, however, the suggestion to forget was
selective in its impact. Although people in the PHA group had difficulty
remembering the content of the movie following the forget suggestion, they had
no difficulty remembering the context in which they saw the movie.

This finding—that PHA temporarily disrupted some people’s ability to recall
the past—echoes decades of hypnosis research. What is entirely new in
Mendelsohn et al.’s study is their demonstration that PHA was associated with
a specific pattern of brain activation. Consistent with what normally occurs in
remembering, when people in the non-PHA group performed the recognition task and
successfully remembered what happened in the movie, fMRI showed high levels of
activity in areas responsible for visualizing scenes (the occipital lobes) and
for analyzing verbally presented scenarios (the left temporal lobe). In stark
contrast, when people in the PHA group performed the recognition task and failed
to remember the content of the movie, fMRI showed little or no activity in these
areas. Also, fMRI showed enhanced activity in another area (the prefrontal
cortex) responsible for regulating activity in other brain areas.

So far, so good. For people in the PHA group, brain activation measured by fMRI
correlated with the failure to remember. But what if reduced activation is
always found in such people regardless of whether they are remembering or
forgetting? We can rule this possibility out because people in the PHA group
showed reduced activation only when they (unsuccessfully) answered questions
about the content of the movie, not when they (successfully) answered questions
about the context of the movie. Indeed, for the context questions, they showed
the same activation as people in the non-PHA group. Perhaps then, the reduced
activation reflects complete forgetting of the information, not just temporary
suppression? We can rule this possibility out also because, in a neat reversal,
people in the PHA group showed normal activation—just as those in the non-PHA
group did—as soon as the suggestion was cancelled.

Hypnosis Is Real
Mendelsohn et al.’s study is important because it demonstrates that hypnotic
suggestions influence brain activity, not just behavior and experience. Hypnotic
effects are real! This fact has been demonstrated clearly in earlier work, for
instance, by psychologist David Oakley (University College London) and
colleagues, who compared brain activation of genuinely hypnotized people given
suggestions for leg paralysis with brain activation of people simply asked to
fake hypnosis and paralysis.

This latest study is also important because it starts to specify the underlying
brain processes, which we assume are shared by PHA and functional amnesia.
Mendelsohn et al. argued that the brain activation seen in PHA reflects a
dampening—some form of rapid, early inhibition of memory material—due to
heightened activity in the prefrontal cortex.

But how does the suppression mechanism decide what to suppress? In this study,
movie content but not movie context was influenced by PHA. Memories involve the
“what,” “how,” “when” and “where” of an event interwoven
together, such that distinctions between content and context may be blurred (for
example, “Was the movie shot with a hand-held camera?”). To make such fine
discriminations, the brain’s suppressor module presumably needs to process
information at a sufficiently high level. Yet this module needs to act quickly,
preconsciously suppressing activation of the information before it even enters
awareness. Brain imaging technologies with superior temporal resolution to fMRI,
such as magnetoencephalography (MEG), might help to resolve this seeming paradox
of sophisticated, yet rapid, operations.

We also wonder how the suppression mechanism in PHA relates to the vast array of
forgetting in the laboratory and in the world? Whereas some forgetting is seen
as strategic, effortful and conscious (say, suppression), other forgetting is
seen as automatic, effortless and unconscious (say, repression). Having mapped
the common features of PHA and functional amnesia, we now need to explore and
compare in greater detail their common processes (such as strategy use,
motivation, level of awareness).

Finally, the neural underpinnings of PHA will be even clearer when we
incorporate its most important aspect in imaging studies—the dissociation
between implicit and explicit memory. In PHA (and in functional amnesia) the
person is unable to explicitly recall certain information, yet we see evidence
of this material on implicit measures. For instance, a participant given PHA may
fail to recall the word “doctor,” learned earlier, but will have no trouble
completing the word fragment “d _ _ t _ r”. Mendelsohn et al. did not assess
implicit memory. Rather, they tested recognition, which in a sense confounds
explicit and implicit memory. We’d like to compare brain scans of a PHA group
trying to explicitly recall the movie (they should show reduced activation, as
above) with brain scans of the same group completing an implicit memory measure
of the movie (they should show normal activation). This would be tricky to
do—implicit measures of complex
material such as movies and autobiographical memories are hard to find or
construct. But it would contribute to a more complete neural picture of the
processes involved in these fascinating forms of forgetting.
Seth-Deborah Roth CRNA,CCHt,CI
www.hypnotherapyforhealth.com
read my blog at www.hypnotichealth.blogspot.com
as seen on the "MythBusters"


www.sethdeborahroth.isagenix.com