SPECIAL TOPICS
EEG Patterns and Hypnotizability
D. Corydon Hammond, PhD, ABPH, ECNS, QEEG-D
Department of Physical Medicine and Rehabilitation, University of Utah School of Medicine, Salt Lake City, UT
Keywords: hypnotizability, EEG, 40 Hz, theta, alpha
After reviewing the relationship of hypnotizability
and EEG activity, a discussion follows of how modifying EEG activity may increase hypnotic responsiveness. This is followed by a brief summary of the relationship of hypnotizability to clinical symptoms.
Biofeedback ⎪ Spring 2005
Relationship of Hypnotic Responsiveness
and EEG Activity
There have been many studies on the relationship of
brainwave activity and hypnotic responsiveness. We
certainly do not have all the answers yet, but this is a
fascinating body of literature. The situation is made
even more complex by the fact that the brain’s activity differs in hypnosis depending on the nature of the
suggestions (e.g., for pain relief, relaxation, hallucinations, etc.).
There is considerable evidence that greater theta
brainwave activity is found in high hypnotizable individuals both in and out of hypnosis. Furthermore, low
and high hypnotizable persons experience an increase
in theta brainwaves when going into hypnosis.
Crawford (1990), for example, reported that high hypnotizable persons exhibited significantly greater power
in the higher theta range (5.5–7.5 Hz) than persons low
in hypnotic responsivity. Schacter (1977) described two
types of theta brainwaves: theta associated with feelings of drowsiness, and another type of theta brainwave associated with focused attention and involved in
complex problem solving (e.g., mental arithmetic). He
believed that enhanced theta activity during problem
solving represented “a combination of selective, narrowly focused processing, and intensive ‘mental
effort’” (p. 59). This kind of theta has been interpreted
as demonstrating strongly focused attention (e.g.,
Inouye, Ishihara, & Shinosaki, 1984, 1985; Mizuki,
1987; Mizuki, Tanaka, Isozaki, & Inanaga, 1976;
Mizuki, Tanaka, Isozaki, Nishijima, & Inanaga, 1980),
and we commonly define hypnosis as being a state of
focused attention and concentration (Hammond, 1998).
Children above the age of 5 have higher hypnotizability than adults, but this responsivity peaks between
the 8- and 12-year-old range and begins decreasing by
ages 13–14 (Olness & Kohen, 1996). Interestingly, the
dominant background brainwave frequency in children
is in the theta frequency band. However, between the
ages of 13 and 14, a shift in brainwave activity occurs
and stabilizes toward the more prevalent adult pattern
in the alpha frequency range. This provides further correlational evidence supporting the role of theta brainwave activity in hypnotic responsivity. Further correlational evidence is found in the fact that corresponding
with the peak of hypnotic responsiveness at ages 8–11,
we also find that the incidence of frontal-midline theta
peaks at this same time is then present in 68.8% of
children (Yamaguchi, 1994). Because of the high hypnotic responsiveness of children, clinicians working
with children are wise to add clinical hypnosis to their
repertoire of therapeutic skills.
An even larger body of hypnosis research implicates the relationship of 40 Hz activity with high
hypnotizability (de Pascalis, 1999), which is another frequency band associated with intensely
focused attention. A common misconception of
hypnosis is that it is synonymous with relaxation.
However, someone can be relaxed and not hypnotized, and hypnotized and not relaxed. Persons can
be involved in an active-alert trance—for instance,
peddling a stationary bicycle— and still experience
the phenomena associated with hypnosis. The central aspect of hypnosis seems to be the highly
focused attention.
There has been some conflicting data on the relationship of alpha and hypnotic response, perhaps in
part due to variability in experimental procedures.
Most recently, Williams and Gruzelier (2001) found
absolute power in high and low alpha and theta associated with hypnotizability and entering hypnosis.
In their study low theta continued to increase after
hypnosis in higher hypnotizable persons, perhaps
suggesting that psychological or health benefits
from hypnosis may be prolonged beyond hypnosis
in more responsive individuals. It was believed that
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EEG Patterns and Hypnotizability
Spring 2005 ⎪ Biofeedback
these changes in theta likely reflect an increase in
relaxation since subjects lower in hypnotizability did
not exhibit many behavioral characteristics associated with hypnosis. The increase in theta was also in
posterior regions (O1 and O2), which would be
anticipated to be more associated with relaxation
than with cognitive processing, and hypnosis in
their study was passive with a low cognitive load.
Higher hypnotizable persons displayed higher alpha
during hypnosis in the posterior cortex, which then
decreased afterward. In contrast, lower hypnotizable
persons displayed a posterior alpha decrease during
hypnosis and an increase after hypnosis. Williams
and Gruzelier (2001) interpreted their results as suggesting, “first, that alpha rather than theta provides
more information about trait differences in high and
low susceptibles and, second, that whereas high susceptibles are able to ‘let go’ during hypnosis and
maintain a state of quiescence with very little attentional or cognitive effort, low susceptibles use more
cognitively active strategies despite the fact that
they reached an increased level of relaxation” (p.
202). Thus they suggested that theta may represent
an index of relaxation, and alpha brainwave activity
represents an index of hypnosis and hypnotic susceptibility. There were, however, limitations in their
study design.
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Increasing Hypnotizability
With two subjects who were minimally responsive to
hypnosis, Wickramasekera (1977) found that after 10
sessions using Tom Budzynski’s Twilight Learner,
where hypnotic suggestions encouraging hypnotic
responsiveness and positive attitudes toward hypnosis
were delivered in a deep theta state, the subjects
increased an average of 6.5 points on a 12-point hypnotizability scale. The opposite suggestions created the
reverse situation in two high hypnotizable subjects.
It is interesting in relation to the finding of
Williams and Gruzelier (2001) that some old research
demonstrated that alpha enhancement neurofeedback
training may be capable of increasing hypnotic
responsivity (Engstrom, London, & Hart, 1970;
London, Cooper, & Engstrom, 1974). In two controlled studies, the Engstrom group demonstrated
that with only six sessions of 8–13 Hz training they
could increase hypnotizability (as measured by the
Stanford Hypnotic Susceptibility Scale [SHSS],
Forms A and B) from 3.16 to 7.42 in the experimental
group, whereas it increased nonsignificantly from 4 to
5.14 in a sham control group who believed they were
receiving alpha neurofeedback but in actuality were
hearing a recording of a successful experimental subject’s production of increased alpha (London et al.,
1974). That study replicated an earlier study
(Engstrom et al., 1970) in which experimental subjects were able to increase their SHSS scores from 3.3
to 7.45. Consider the implications that may have for
increasing hypnotic capacity in chronic pain patients.
Kroger and Schneider (1959) described the use of a
“brain-wave synchronizer” that provided photic stimulation in the alpha brainwave range, which they
claimed promoted a hypnotic trance state. Hammer
and Arkins (1964) evaluated the effects of the photic
stimulation on the passage of a difficult hypnotic suggestion. The machine was set (a) in the 10–11 Hz
range as the only form of hypnotic induction for 15
minutes, (b) in accompaniment with a standard hypnotic induction (while still set at 10-11 Hz), and (c) in
accompaniment with a verbal induction while set at 30
Hz. They discovered that when photic stimulation was
used alone, without a verbal hypnotic induction with
it, it proved ineffective in facilitating a response to the
test suggestion. This finding discouraged any further
work using photic stimulation with hypnosis. This is
unfortunate because an overlooked finding by
Hammer and Arkins (1964) was that “the addition of
a particular sort of photic driving probably improves
trance induction” (p. 81), which was when it was set at
the 10-11 Hz level. At this setting, it facilitated
increased responsiveness over verbal hypnotic procedures alone. Furthermore, this effect may be specific to
the alpha (and I would speculate, to the theta) range of
stimulation, because when photic stimulation accompanying a hypnotic induction was at 30 Hz, there was
no enhancement in suggestive response.
Relationship of Hypnotic Responsivity
and Clinical Symptoms
Although most highly hypnotizable individuals do not
manifest psychopathology, hypnotic responsivity has
been found to be associated with some clinical conditions. For instance, above average hypnotizability has
been found in patients with bulimia or purging
anorexia, more severe hyperemesis gravidarum in
pregnancy, posttraumatic stress disorder symptoms,
insomnia, nightmares, temporomandibular joint and
other chronic pain syndromes, more intense urticaria
Hammond
symptoms, more severe migraines, conversion disorders, dissociative disorders, phobias, mild head injuries,
and attention deficit disorder/attention deficit hyperactivity disorder (ADD/ADHD). The latter two conditions are particularly interesting in light of research on
EEG patterns associated with hypnotic responsiveness
because the most common patterns associated with
traumatic brain injury and ADD are an excess of theta
brainwave activity. Below average hypnotic responsiveness is usually found in patients with obsessive
compulsive disorder. These are persons who tend to be
very externally focused, exhibiting higher levels of
beta brainwaves. They have difficulty disengaging
from the environment and from an external focus of
attention to become highly absorbed and focused
internally. Wickramasekera (2005) discusses the relationship between hypnotic responsiveness and “surplus empathy” and “surplus pattern recognition.”
References
D. Corydon
Hammond
Correspondence: D. Corydon Hammond, PhD, ABPH, ECNS, QEEG-D,
Physical Medicine & Rehabilitation at the University of Utah School of
Medicine, 30 North 1900 East, Salt Lake City, UT 84132-2119, email:
d.c.hammond@m.cc.utah.edu.
Biofeedback ⎪ Spring 2005
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