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Original Research Paper
Functional changes in brain activity after hypnosis in patients
with dental phobia
Ulrike Halsband
a,
⇑
, Thomas Gerhard Wolf
b
a
Department of Psychology, Neuropsychology, University of Freiburg, Germany
b
Department of Operative Dentistry, University Medical Center, University of Mainz, Germany
article info
Article history:
Received 12 January 2016
Received in revised form 4 October 2016
Accepted 5 October 2016
Available online xxxx
Keywords:
Dental phobia
Fear
Hypnosis
Functional brain activity changes
fMRI
Amygdala
Anterior cingulate cortex
Hippocampus
Insula
abstract
Visiting the dentist is often accompanied by apprehension or anxiety. People, who suffer from specific
dental phobia (a disproportional fear of dental) procedures show psychological and physiological symp-
toms which make dental treatments difficult or impossible. For such purposes, hypnosis is often used in
dental practice as an alternative for a number of treatments adjuvant or instead of sedation or general
anaesthetics, as medication is often associated with risks and side effects. This is the first study to address
the effects of a brief dental hypnosis on the fear processing structures of the brain in dental phobics using
functional magnetic resonance imaging (fMRI). 12 dental phobics (DP; mean 34.9 years) and 12 healthy
controls (CO; mean 33.2 years) were scanned with a 3 T MRI whole body-scanner observing brain activity
changes after a brief hypnotic invervention. An fMRI event-related design symptom provocation task
applying animated audio-visual pseudorandomized strong phobic stimuli was presented in order to max-
imize the fearful reactions during scanning. Control videos showed the use of familiar electronic house-
hold equipment.
In DP group, main effects of fear condition were found in the left amygdala and bilaterally in the ante-
rior cingulate cortex (ACC), insula and hippocampu (R < L). During hypnosis DP showed a significantly
reduced activation in all of these areas. Reduced neural activity patterns were also found in the control
group. No amygdala activation was detected in healthy subjects in the two experimental conditions.
Compared to DP, CO showed less bilateral activation in the insula and ACC in the awake condition.
Findings show that anxiety-provoking stimuli such as undergoing dental surgery, endodontic treatments
or insufficient anaesthetics, can be effectively reduced under hypnosis. The present study gives scientific
evidence that hypnosis is a powerful and successful method for inhibiting the reaction of the fear cir-
cuitry structures.
!2016 Published by Elsevier Ltd.
1. Introduction
Most people show some kind of apprehension or anxiety when
they have to go for a dental treatment. According to Stouthard and
Hoogstraten (1990) 40% reported that they were anxious about
dental treatment and 10% indicated to have severe anxiety when
visiting a dentist.
However, subjects with dental anxiety or dental fear are differ-
entiated from patients with a dental phobia (DP), suffering from a
disproportional fear of (invasive) dental procedures by the severity
of their psychological and physiological symptoms. The phobic
stimulus is avoided. Triggers of fear are the perception of multi-
modal sensory stimuli, including visual (the sight of the dentist,
the dentist’s chair and the surgery kit), auditory (e.g. the sound
of a drill) and olfactory (the smell of the dentist’s surgery room).
Phobic patients may suffer from a traumatic experience caused
by previous treatments. Oosterink et al. (2008) carefully analysed
the anxiety-provoking capacity of a large set of dental stimuli.
Results indicate that invasive stimuli such as surgical procedures
were rated as the most anxiety provoking stimuli. The most fearful
stimuli were as follows (ranked in order of anxiety provoking): (1)
having dental surgery, (2) having some gum burned away, (3) hav-
ing a root canal treatment, (4) insufficient anaesthetics and (5)
extractions of a tooth.
According to DSM-IV-TR dental phobia (DP) is classified as a
specific phobia of the blood-injection-injury phobia (B-I-I). How-
ever, recent evidence (van Houtem et al., 2014) suggests that DP
and B-I-I are independent subtypes. DP patients rated typical
http://dx.doi.org/10.1016/j.jphysparis.2016.10.001
0928-4257/!2016 Published by Elsevier Ltd.
⇑
Corresponding author at: Department of Psychology, Neuropsychology, Univer-
sity of Freiburg, Engelbergerstr. 41, D-79085 Freiburg, Germany.
E-mail address: halsband@psychologie.uni-freiburg.de (U. Halsband).
Journal of Physiology - Paris xxx (2016) xxx–xxx
Contents lists available at ScienceDirect
Journal of Physiology - Paris
journal homepage: www.elsevier.com/locate/jphysparis
Please cite this article in press as: Halsband, U., Wolf, T.G. Functional changes in brain activity after hypnosis in patients with dental phobia. J. Physiol.
(2016), http://dx.doi.org/10.1016/j.jphysparis.2016.10.001
B-I-I phobic stimuli, like the sight of blood, significantly lower as
compared to individuals with B-I-I. Patients with DP showed a high
level of fear to multiple stimuli, particularly involving invasive pro-
cedures, but they are not afraid of blood or injections per se. Also,
95% of the patients with DP showed avoidance behavior for dental
care, but only 13% of the dental phobics reported a history of faint-
ing during dental treatment. The authors concluded that DP should
be considered as a specific subtype in the DSM classification sys-
tem independent of B-I-I.
Several authors reported about the good acceptance of hypnosis
in DP patients and their effectiveness in reducing pain and anxiety
(Abdeshahi et al., 2013; Fabian et al., 2009; Glaesmer et al., 2015;
Halsband, 2011; Schmierer and Schuetz, 2008). Positive effects of
hypnosis in patients with dental phobias include prevention of
avoidance behavior and the resulting lack of dental treatment,
reduction of extreme fear and anxiety, reduced felt pain, less
bleeding during tooth extractions and better and faster wound
healing. Taken together, a successful implementation of hyp-
notherapeutic interventions in dental treatments has positive
effects on both the extreme fear and the felt pain of the patients
while side effects are reduced to a minimum. An improvement of
the subjective experience of a dental treatment is highly
relevant to prevent avoidance behavior and the resulting lack of
dental care.
In daily dental practice many dentists have to cope with a large
number of patients. This means that often there is little additional
time available to help the patient to overcome his fears and anxi-
eties. Also, a dental surgery may be urgent, e.g. in case of a root
canal treatment, so there is not enough time to allow the patient
to enter a hypnotherapy with a local specialist which may last sev-
eral weeks. Thus, short hypnotic interventions performed by the
dentist himself have become an important and effective method
to help these patients to enter therapy. Therefore, in the present
study we examined the effects of such a short dental hypnosis on
the neural mechanisms of DP patients.
Several studies looked at the neural mechanisms of dental pho-
bias (e.g. Caseras et al., 2010a; Hilbert et al., 2014, 2015; Lueken
et al., 2011a, 2011b, 2014; Scharmueller et al., 2015; Schienle
et al., 2013). Results suggest different neural response patterns in
DP as compared to snake phobics (Lueken et al., 2011a). Schienle
et al. (2013) reported about gender specific brain activation pat-
terns: males presented with a greater activation of the caudate
nucleus, females showed an enhanced dorsolateral prefrontal cor-
tex involvement. Muensterkoetter et al. (2015) reported about dif-
ferent neural correlates of sustained vs. phasic fear in phobics.
Phasic fear was accompanied by a strong amygdala activation,
whereas sustained fear was characterized by an activation in the
insula, anterior cingulate cortex (ACC) and the bed nucleus of the
stria terminalis.
Why to study the mechanisms of dental phobia and the effect of
a hypnotic intervention? To examine dental phobia is unique since
no other body part has been strongly associated with a specific
phobia. Meyer et al. (2014) reported about an enhanced suscepti-
bility of tooth pain to fear conditioning. Results showed an
enhanced amygdala and orbitofrontal cortex activity in the first
half of the conditioning procedure. Their findings are in agreement
with previous fear conditioning studies which indicate that the
amygdala is involved during the initial phase only (Büchel et al.,
1998; LaBar et al., 1998).
The amygdala, insula and anterior cingulate cortex (ACC)
form a crucial part of the so-called ‘‘anxiety circuit” put forth by
Etkin and Wager (2007). More recently, Bruehl et al. (2014) con-
firmed the hyperactivation of the fear circuit. The insula is typically
coactivated together with the amygdala (Kohn et al., 2014;
Robinson et al., 2010) especially during emotion processing
(Stein et al., 2007) and has been shown to be involved in processing
stimuli evoking disgust as an emotional response and in the repre-
sentation of interoceptive information (Chen et al., 2009).
We aimed to investigate whether these structures can be acti-
vated in dental phobics and whether a brief dental hypnosis has
direct enhancing effects on the neural activity patterns in these
fear circuitry structures. We also hypothesized that in many
patients with dental phobias strong fearful reactions can be traced
to a triggering of traumatic recollections associated with previous
dental treatments. Therefore we expected a significant increase in
hippocampal activity in the awake state and a reduction in hip-
pocampal activity during hypnosis.
Not using any kind of hypnotic intervention Lueken et al.
(2011a, 2011b, 2014) investigated in very well-controlled and sys-
tematic studies neural activity in patients with specific phobias
(dental phobia as compared to snake phobia). Interestingly, in den-
tal phobics no defensive mechanisms in the amygdala and the hip-
pocampus were observed after the presentation of phobic stimulus
material. However, one may question whether the phobic stimuli
used in their study were strong enough to elicit the maximum of
fear responses. For instance, Lueken et al. (2011a, 2011b) showed
a video when a dentist puts on his latex gloves to prepare for the
treatment. We hypothesized that an activation in the amygdala,
ACC, insula and hippocampus may occur in these patients if we
use extremely strong phobia-inducing video material. We wanted
to find stimuli which are very highly frightening for patients suf-
fering from a dental phobia- they also had to be specifically con-
nected with dental treatments. We therefore performed an
extensive preliminary investigation in order to ensure that only
those video-clips were used which had a very high potential of fear
inducing capacity. No videos were shown which illustrated more
general preparations for a hygienic medical treatment like putting
on sterile gloves. Our preliminary study was based on a different
group of subjects. They were asked to rank the video material on
a rating scale according to their feelings of dislike. Only those stim-
uli which were judged to be most frightening/disgusting were
included in the present investigation. Full details are presented
in the section ‘‘preliminary investigation”. In addition we hypoth-
esized that normal control subjects (CO) would show a measurable
brain reaction to the negative video material. We postulated that
these brain regions are less activated in CO as compared to our
phobic patients because the video material did not appear to be
extremely frightening to them.
However, in our extensive preliminary investigation (Halsband,
2011; Strickner and Halsband, 2010) our control subjects ranked
the dental stimuli as very disgusting and unpleasant to look at.
We therefore postulated that hypnosis would also result in a
decrease in brain activation in our normal subjects. This hypothesis
is supported by recent fMRI findings by Jiang et al. (2016). The
authors showed in highly hypnotizable healthy subjects under
hypnosis plasticity changes in the ACC and insula. It was concluded
that there is a altered state of attention under hypnosis and a mod-
ified body awareness. Furthermore, in a fMRI study by Robinson
et al. (2016) it was shown that attentional control can modulate
activity within anxiety potentiated amygdala-frontal coupling in
healthy subjects. When subjects were instructed to shift their
attention away from threatening emotional stimuli a correspond-
ing down regulation of circuit coupling was observed despite the
fact that the threatening context of the stimuli remained. Hypnosis
is an example of a psychological intervention by which attentional
control can modulate the neural circuitry of fear and anxiety. In
hypnosis, sensory processing is limited and determined by sugges-
tions. In accordance with the findings by Robinson et al. (2016) we
hypothesized that a shift of attention away from the threatening
and disgusting character of the dental stimuli may result in a
reduction of activity after hypnotic induction in our healthy sub-
jects as well as in our phobic patients.
2U. Halsband, T.G. Wolf / Journal of Physiology - Paris xxx (2016) xxx–xxx
Please cite this article in press as: Halsband, U., Wolf, T.G. Functional changes in brain activity after hypnosis in patients with dental phobia. J. Physiol.
(2016), http://dx.doi.org/10.1016/j.jphysparis.2016.10.001
This is the first study to address the effects of a brief dental hyp-
nosis on the fear processing structures of the brain and the hip-
pocampus in dental phobics and in healthy subjects. Using
functional magnetic resonance imaging (fMRI) DP patients and
control subjects were presented animated video clips with strong
phobic dental stimuli. Brain activation patterns were analyzed
under hypnosis and in the awake state of the subjects. Our findings
argue for a broader implementation of hypnotic interventions in
dentistry.
2. Materials and methods
2.1. Preliminary investigation
Before the start of our main experiment an extensive prelimi-
nary investigation was carried out. There are two articles published
in German about our preliminary program (Halsband, 2011;
Strickner and Halsband, 2010). The aim of our preliminary study
was to develop an experimental design which proves to be robust
and reliable. In this context we tested in 15 subjects (7 dental pho-
bics and 8 controls) the effects of the phobia-inducing video clips
and their intensity on the subjects’ reactions using a rating scale
from 1 to 7 (whereby 7 was the highest negative ranking and 1
was the lowest). Only those stimuli which proved to be able to cre-
ate a strong emotional reaction (mean rating > or = 4) were
included in our main study. All video scenes which were ranked
to be lower than 4 on the negative ranking scale were dismissed
from our main investigation.
Subjects were asked to describe their feelings when confronted
with the video clips. Interestingly, negative ratings given by the
phobic group were mainly based on a feeling of fear and distress,
in contrast, our control subjects showed a strong tendency to rank
the stimuli in terms of disgust or a feeling of ugliness.
We also tested for a possible effect of the order of presenta-
tion (awake vs hypnotic state). Eight subjects were shown the
dental video clips in the fMRI-scanner. Half of the subjects were
first tested under hypnosis, thereafter in the awake state, the
other half was tested vice versa. Results showed no significant
differences in their responses irrespective of whether the sub-
jects were first tested under hypnosis or in the awake condition.
This finding strongly argues against a possible bias that subjects
reacted with less fear in the second experimental condition sim-
ply because they got more used to the intense phobic stimuli.
We therefore decided to present the stimuli in the following
order: awake state followed by hypnosis. The reasons were as
follows:
(1) There is evidence about possible after-effects after a hyp-
notic induction (Stanley and Burrows, 2001) which in indi-
vidual subjects could interfere with the response to the
succeeding stimulus presentation.
(2) Some of our subjects reported about a feeling of deep relax-
ation or even tiredness after hypnosis, and they complained
about the negative effects of a sudden and abrupt change
immediately thereafter when the phobic stimuli were pre-
sented without hypnosis. This induced a feeling of strong
and sometimes even prolonged discomfort which was still
present when they left the scanner room. Some of our sub-
jects got very angry and told us that they would never ever
been willing to participate again in such an experiment. In
contrast, when hypnosis was presented at the end of the
experimental session, subjects were usually in a relaxed
and balanced mood. Thus, also for ethical reasons we
decided to have the hypnotic session at the end of the
experiment.
2.2. Main experiment
2.2.1. Subjects
Twelve dental phobics (DP) and twelve healthy controls (CO)
were recruited from a pool of participants from advertisements
in local newspapers. Age-matched subjects who presented with a
low anxiety score of dental treatment served as a control group.
The mean age of the experimental subjects was 34.9 years (range
24–57 years) and 33.15 years (range 19–52 years) for the control
group. There were eight female and four male subjects in the
experimental group and six male and six females in the control
group. The enrollment of our experimental subjects is shown in
Fig. 1.
In total, 25 subjects who claimed to have an extreme dental fear
were psychologically assessed for eligibility by means of psycho-
logical testing and personal interviews. Eight subjects had to be
excluded after the first contact because they did not meet our
inclusion criteria or because they decided not to participate in
the succeeding fMRI study. Out of the remaining 17 subjects allo-
cated to our fMRI study, four subjects had to be excluded which left
us with a sample size of twelve dental phobics (see Fig. 2). In addi-
tion, twelve age-matched healthy controls participated in our
study.
2.2.2. Psychological testing
Before the experiment all subjects were evaluated on a battery
of psychological tests. Full details are shown in Table 1.
Subjects were tested on three questionnaires for dental fear: (i)
Dental Fear Survey (DFS, Toennies et al., 2002), (ii) Hierarchical
Anxiety Questionnaire (HAQ, Joehren, 1999a which is the most
commonly used questionnaire to assess dental anxiety in German
speaking countries) and (iii) Dental Anxiety Scale revised (DAS-R,
Corah, 1969). Subjects were classified as dental phobics when they
reached a sum score of 70 or above in the DFS indicating moderate
to severe dental phobia combined with a score of >35 of HAQ and/
or in the upper quartiles of DAS-R. Scores obtained on the DFS
strongly correlated with the results of DAS-R and HAQ. All subjects
showed an avoidance behavior to see a dentist.
Normal controls presented with a sum score of 33 or below in
the DFS and they scored in the lower quartiles of HAQ and DAS-
R. Additionally, the sample was characterized via questionnaires
on general anxiety (STAI; Laux et al., 1981). Only right-handed sub-
jects were admitted to the present investigation (Edinburgh Inven-
tory of Handedness, Oldfield, 1971).
Subjects had to be susceptible to hypnosis. This was assessed by
means of the Harvard Group Scale of Hypnotic Susceptibility
(HGSH; Shor and Orne, 1962) and a live hypnosis performed by
U.H. Only subjects with a score of P7 on the HGS who also showed
a positive response to the hypnotic induction were allowed to par-
ticipate in the study. Hypnotic induction lasted for 25 min and was
performed in small groups with a maximum of four participants.
All subjects had to fill in a subjective rating scale of relaxation
(ranging from 1 to 10) where 1 was the lowest and 10 the highest
mark of relaxation. The questionnaire had to be filled in before and
after hypnosis. Subjects who indicated that they felt more relaxed
after hypnosis were included in the present study. Additionally
subjects reported about a time distortion after hypnotic induction
which has been repeatedly described as a phenomenon of a suc-
cessful hypnotic trance (Halsband et al., 2009).
Exclusion criteria were mental disorders as assessed by the
German version of a structured clinical interview for DSM SCID,
psychopharmacological medication, pregnancy or neurological dis-
ease. In addition fMRI-related exclusion criteria were used such as
metal or electronic implants in their bodies (e.g. pacemakers,
aneurysm clips), metallic tattoos, phobic reactions to the scanner
or a history of fainting.
U. Halsband, T.G. Wolf / Journal of Physiology - Paris xxx (2016) xxx–xxx 3
Please cite this article in press as: Halsband, U., Wolf, T.G. Functional changes in brain activity after hypnosis in patients with dental phobia. J. Physiol.
(2016), http://dx.doi.org/10.1016/j.jphysparis.2016.10.001
All procedures were approved by the Ethical Committee of Frei-
burg University. The standards of the Declaration of Helsinki were
met. All subjects provided written informed consent and received a
financial compensation for their effort.
2.2.3. Experimental design
An fMRI event-related design symptom provocation task apply-
ing audio-visual stimuli was delivered on Presentation 12.0 (Neu-
robehavioral Systems, Albany, CA, USA) software and presented
to subjects via head mirrors during scanning. Audio-visual stimuli
comprised a set of 25 dental videos for the experimental condition,
E (dental drillers, etc.) and 25 control videos, C (electronic house-
hold instruments). Each video was 5 seconds in length. Dental
and control stimuli were presented in pseudorandomized blocks
of 5 videos each at a time. Stimuli were separated by an interstim-
ulus interval (ITI) of varying length ranging between 11 and 15 s
(count-down mechanism). Pseudorandomized sequential arrange-
ment of stimuli allowed a maximum of three repetitions per con-
dition, e.g. E-C-C-E-C-E-E-C-C-E-E-E. Sufficient volume was used
in both experimental conditions such that sounds were well dis-
criminated above scanner noise but not uncomfortable. The loud-
ness was identical in the experimental and the control
conditions. Full details on our experimental set-up are shown in
Fig. 2.
2.2.4. Hypnotic induction
Hypnotic induction was performed by a professional dentist
qualified in dental hypnosis (Markovici-Decker). The induction
Fig. 1. Enrollment of experimental subjects.
4U. Halsband, T.G. Wolf / Journal of Physiology - Paris xxx (2016) xxx–xxx
Please cite this article in press as: Halsband, U., Wolf, T.G. Functional changes in brain activity after hypnosis in patients with dental phobia. J. Physiol.
(2016), http://dx.doi.org/10.1016/j.jphysparis.2016.10.001
was audio-taped and lasted for 20 min. In the scanner it was deliv-
ered via earphones to the subjects. The aim of the hypnosis was to
achieve a global mental and physical relaxation. This included
breathing awareness, feelings of warmth, positive mood inductions
and creation of positive imagery. Subjects were instructed to keep
their eyes open and to attend to the forth-coming video-clips.
Our hypnotic induction was based on the principles developed
by Fiedler (2006) for the treatment of dental phobias. The main
concept is that three key words particularly associated with a feel-
ing of deep relaxation were presented before the presentation of
the stimuli. Important to know is that these words were individu-
ally chosen in advance by our subjects. Typical examples of words
chosen are ‘‘sun-beach-sea” or ‘‘caribics-holidays-palm trees”.
Every subject had chosen those words which would trigger the
best possible association with happiness and relaxation. Subjects
informed us about five days before scanning which words they
had selected. These words were slowly spoken, audio-taped and
integrated into our stimulus presentation. In the awake condition
non-sense words were used as a control. We believe that this indi-
vidual approach under hypnosis helped our subjects to reach a
maximum of relaxation. For instance, if a person is particularly
fond of mountain climbing it is unlikely that he would chose an
association connected with the sea side.
2.3. fMRI data acquisition
All subjects were scanned at the University Hospital Freiburg
using a 3 T MRI whole-body scanner (Siemens, Erlangen, Germany)
and a 12 channel head coil. Functional images were acquired via
T2⁄weighted gradient echo planar imaging (EPI) covering the
whole brain (460 volumes, repetition time (TR) 2.145 s, echo time
(TE) 25 ms. 41 axial slices were recorded in tilted angle (parallel to
the temporal lobe) interleaved acquisition, no gap, slice thickness
2 mm.
FMRI data were analyzed using SPM12 (Wellcome Trust Centre
for Neuroimaging, UCL, London, UK). Images were realigned and
unwarped to correct for head movement, applying a fieldmap cor-
rection to the EPI time series (FBI motion correction, Churchill
et al., 2012). Scans from subjects with head motion of more than
3.0 mm in the x, y or z direction and more than 1.0"of rotation
about each axis were excluded from the present analysis.
Five dummy volumes were discarded with regard to T1 equili-
bration effects to ensure stability of the imaging data. The T1
weighted structural reference image was acquired via Magnetiza-
tion Prepared Rapid Gradient Echo Imaging (MPRAGE;176 sagittal
slices, slice thickness = 1 mm, TE = 2.26 ms, TR = 1900 ms,
FOV = 256 mm !256 mm. Structural and functional images were
co-registered, segmented, and normalized to the MNI reference
brain (Montreal Neurological Institute, Quebec, Canada). The rea-
ligned images were spatially normalized to the EPI template in
SPM12 and re-sampled to 2 !2!2 mm voxel size. An 8 mm
full-width half-maximum Gaussian kernel was applied for spatial
smoothing. Headphones were applied for stimulus presentation,
as hearing protection and to allow communication with the
subject.
This is a mixed-design with repeated measurements (hypnosis
vs awake state) in two subject groups (DP, CO) under two stimulus
conditions: phobic stimuli, PS vs neutral, NS i.e. D (dental) vs E
(electrical household equipment). Furthermore, it is a similar com-
plex fMRI design involving within- and between-group compar-
isons as previously described by Neumann et al. (2003).We
followed their practical advice how to handle a repeated measure-
ment design with different subject groups. The subjects factor,
group factor and the condition factor were specified and an inter-
action was modeled. Statistical parametric maps of t-values (SPM
(t)) were created for each participant using SPM12. In order to
achieve a sensitive determination of group differences as well as
consistency across subjects for each task and condition, data from
Fig. 2. Experimental design.
Table 1
Psychological test battery.
Psychological testing
"Dental Fear Survey (DFS, Toennies et al., 2002)
"Hierarchical Anxiety Questionnaire (HAQ, Joehren, 1999b): most commonly used questionnaire for dental anxiety in German speaking countries
"Dental Anxiety Scale (DAS, Corah, 1969)
"Structured Clinical Interview for DSM (SCID, German version, Wittchen and Pfister, 1997)
"State-Trait-Anxiety Inventory (STAI, Laux et al., 1981)
"Harvard Group Scale of Hypnotic Susceptibility (HGSHS, Shor and Orne, 1962)
"Live Hypnosis (Halsband)
"Edinburgh Inventory of Handedness (Oldfield, 1971)
U. Halsband, T.G. Wolf / Journal of Physiology - Paris xxx (2016) xxx–xxx 5
Please cite this article in press as: Halsband, U., Wolf, T.G. Functional changes in brain activity after hypnosis in patients with dental phobia. J. Physiol.
(2016), http://dx.doi.org/10.1016/j.jphysparis.2016.10.001
all 12 DP and for the 12 CO that were obtained before and after
hypnotic therapy underwent a joint statistical analysis (fixed-
effects analysis). Common as well as differential activations of
the group averages were determined by the specification of appro-
priate contrasts as described by Preibisch et al. (2003). Within-
group comparisons (hypnotic therapy, HT versus awake state, AS)
were performed. Corrections for multiple non-independent com-
parisons were made in accordance with Gaussian random field the-
ory. The subjects factor, group factor (HC, DP), and stimulus factor
were specified and an additional interaction between group and
stimulus factors was modeled. In order to remove low frequency
fluctuations in the BOLD signal, a high-pass filter was used. Con-
trasts against baseline-stimuli were computed and transferred into
a flexible factorial second-level design.
For each subject, four regressors of interest (preFEAR > post-
FEAR, preCONTROL > postCONTROL, preFEAR > preCONTROL, and
postFEAR > postCONTROL) and the six-movement parameters from
the rigid body transformation as regressors of no interest were
introduced to the general linear model. Contrasts of interests were
DP: (PS > NS) HT > AS, CO: (PS > NS) HT > AS, DP > CO, HT: PS > NS,
DP > CO, HT > AS, AS: DP (PS > NS) > CO, PS > NS, PS: DP > CO,
HT > AS, PS > NS, NS: (PS > NS) HT > AS, DP > CO. Differences in
functional activation patterns between the dental phobic group
and our healthy controls were directly compared when presented
with the fearful or neutral stimuli. A within subject comparison
was made to test for differences in functional activation in the
awake condition as compared to a hypnotic therapy. Results were
included in a full factorial model on group level. An eye-tracking
system was used for monitoring the movement of the subject’s
eye in order to ensure that the subject was really looking at the
video scenes.
3. Results
According to our hypotheses a region of interest analysis (ROI)
was conducted for the following selected brain regions: amygdala,
ACC, insula and hippocampus. ROI analyzes on brain activations
are given in Tables 2 and 3.
3.1. Within-group comparisons (before hypnosis versus after therapy)
Analysis of the amygdala as one of our key targets revealed a
significant reduction of the left amygdala activity after hypnosis
(Fig. 3). A comparison of the DP group for the contrast awake con-
dition > hypnosis showed a significant left amygdala activation
(p < 0.001) when presented with the phobic stimulus (Fig. 3, left
side), in contrast, no significant amygdala activation was found
after dental hypnosis (Fig. 3, right side). Control subjects showed
no amygdala activation in the awake state and also no activation
under hypnosis, therefore no pictorial presentation is shown.
Immediately after hypnotic therapy we detected in DP a signif-
icant bilateral reduction in activation in the ACC, insula and the
hippocampus. In Fig. 4a comparison of the DP group for the con-
trast awake condition > hypnosis is shown for the awake condition
(left) and hypnosis (right) for the following structures: ACC (top),
insula (middle) and hippocampus (down). Contrast revealed a
higher activity in the right hippocampus as compared to the left
side (p < 0.05). After a brief hypnotic intervention, DP showed a
significantly reduced activation in these areas (p < 0.01).
In the awake condition, CO showed a bilateral activation in the
insula and ACC (p < 0.001). However, the activations in the control
group were less pronounced as compared to DP (p < 0.001). Inter-
estingly, the short dental hypnotic intervention reduced the neural
activity patterns also in the control group (p < 0.001). There was a
bilateral activation in the hippocampus present in the awake con-
dition (p < 0.005) which disappeared under hypnosis in these
subjects.
3.2. Between-group comparisons (DP versus CO)
In the awake state, we detected significantly higher activations
in DP when confronted with the phobic stimuli as compared to our
Table 2
ROI analysis on brain activations during the presentation of dental stimuli for the between-group comparisons in pre-selected brain regions.
Region Side MNI t P corr.
xyz
Before hypnosis: Higher activations in DP in the awake state than in CO
Stimulus: dental (PS < NS)
DP < CO
Amygdala L 18 #10 #12 5.23 <0.001
R No differential activations
Insula L 42 #6 14 4.18 <0.001
R 45 26 #3 4.02 <0.001
Hippocampus L #22 #16 #14 4.86 <0.005
R 28 #24 #10 5.12 <0.001
ACC L 29 21 19 4.19 <0.001
R 6 23 25 4.41 <0.001
After hypnosis: More pronounced reductions in activations in DP than in CO
Stimulus: dental (PS < NS)
DP < CO
Amygdala L #22 #7#14 4.13 <0.001
R No differential activations
Insula L #40 #4 18 4.55 <0.001
R#28 19 #6 4.33 <0.001
Hippocampus L 23 #9#14 4.63 <0.005
R 42 19 #12 4.54 <0.001
ACC L 3 32 15 4.87 <0.001
R 6 27 18 4.21 <0.001
No differential activations for the presentation of the neutral stimuli.
DP, dental phobics, CO, healthy controls, PS phobic dental stimuli, NS, neutral stimuli, HT, L left side, R right side, x, y, z MNI, Montreal Neurological Institute template: x, y and
z are the coordinates of the region. In case multiple foci were identified in a given region, only the one with the highest t-value is shown. P corrected < 0.05.
6U. Halsband, T.G. Wolf / Journal of Physiology - Paris xxx (2016) xxx–xxx
Please cite this article in press as: Halsband, U., Wolf, T.G. Functional changes in brain activity after hypnosis in patients with dental phobia. J. Physiol.
(2016), http://dx.doi.org/10.1016/j.jphysparis.2016.10.001
CO in the left amygdala, bilateral ACC, bilateral insula and bilateral
hippocampus (p > 0.001) (R < L, p < 0.005). In the awake state a
pronounced left-sided amygdala activation was observed in our
DP when presented with the phobic stimuli (p < 0.01). In contrast,
no significant amygdala activations were detected in our CO. We
also detected significantly higher bilateral activations in the ACC
and the insula in DP as compared to our CO (p < 0.001). In the
awake condition, CO also showed a bilateral activation in the insula
and ACC (p < 0.001) when confronted with the dental stimuli, but
the activations in the control group were less pronounced as com-
pared to DP (p < 0.001). In addition, in the awake state DP showed
a bilateral hippocampal activation which was more pronounced on
the right side (p < 0.005).
No amygdala activation was detected in our healthy subjects in
the two experimental conditions (awake versus hypnosis). In the
awake condition, CO showed a bilateral activation in the insula
and ACC (p < 0.001). The activations in the control group were less
pronounced as compared to DP (p < 0.001). Interestingly, the short
dental hypnotic intervention reduced the neural activity patterns
in the insula and the ACC also in the control group (p < 0.001). In
the hippocampus, there was a bilateral activation present in the
awake condition (p < 0.005) which disappeared under hypnosis
in CO subjects.
4. Discussion
Hypnosis is a psychological intervention by which attentional
control can modulate the neural circuitry of fear and anxiety and
interact with structures related to unpleasant memories. This
study investigated the effects of a brief dental hypnosis on pre-
selected areas of the fear processing structures of the brain (amyg-
dala, ACC and insula) and the hippocampus in dental phobics and
in healthy subjects. Using fMRI, DP patients and CO were presented
animated video clips with strong fearful dental stimuli as com-
pared to neutral stimuli. Brain activation patterns were analyzed
under hypnosis and in the awake state. We confirmed our hypoth-
esis that hypnosis alters the neural activation patterns in these
brain areas. Our main findings were as follows:
1. DP: We observed a significant reduction of neural activity after
hypnotic induction in the left amygdala, bilateral ACC, bilateral
insula and bilateral hippocampus (R < L).
2. CO: Hypnosis also reduced the neural activity patterns in CO in
the insula and the ACC. Under hypnosis, no activation was
found in the hippocampus, though a bilateral activation was
present in the awake condition. Within the amygdala no activa-
tion was found in the awake state or under hypnosis.
Table 3
Localization of peak activations during the presentation of dental stimuli for the within-group comparisons in pre-selected brain regions.
Region Side MNI t P corr.
xyz
Reduced activations in DP after hypnotic induction for the contrast HT > AS (DP > CO)
Amygdala L 26 #8#12 4.69 <0.001
R No differential activations
Insula L 34 12 13 4.65 <0.001
R#22 3 3 4.87 <0.001
Hippocampus L 18 #5#12 4.68 <0.005
R 21 #9#14 5.13 <0.001
ACC L 19 43 19 4.78 <0.001
R 6 28 25 5.21 <0.001
No differential activations for the presentation of the neutral stimuli.
DP, dental phobics, CO, healthy controls, HT, hypnotic therapy, AS, awake state, L left side, R right side, x, y, z MNI, Montreal Neurological Institute template: x, y and z are the
coordinates of the region. In case multiple foci were identified in a given region, only the one with the highest t-value is shown. P corrected < 0.05.
Fig. 3. Neural activation patterns of dental phobic patients in the amygdala for dental fearful stimuli (PS > NS) before (left) and after hypnosis (right) (preFEAR > postFEAR) PS
phobic stimuli, NS neutral stimuli.
U. Halsband, T.G. Wolf / Journal of Physiology - Paris xxx (2016) xxx–xxx 7
Please cite this article in press as: Halsband, U., Wolf, T.G. Functional changes in brain activity after hypnosis in patients with dental phobia. J. Physiol.
(2016), http://dx.doi.org/10.1016/j.jphysparis.2016.10.001
Taken together our findings seem to indicate that a hypnotic
intervention is a powerful method to reduce the response patterns
to fearful (DP) and/or unpleasant stimuli (CO) presentations.
For many people a visit to the dentist is often accompanied by
fear; around 11% even suffer from dental phobia (Enkling et al.,
2006). Reasons for fear and phobia can vary. Besides the feeling
of physiological responses such as sweating or increased heart rate,
avoidance behavior, including failure to appear for appointments,
are reported (Berggren and Meynert, 1984; Erten et al., 2006;
Enkling et al., 2006). Nowadays hypnosis is a routinely used tech-
nique in dentistry. In situations when most behavioral techniques
fail, medication or anesthesia are contraindicated or declined by
the patient, hypnosis is able to help (Peretz et al., 2013). Pain, anx-
iety and haemorrhage can be effectively reduced through hypnotic
intervention (Huet et al., 2011; Abdeshahi et al., 2013; Glaesmer
et al., 2015). Furthermore, hypnosis can be presented as a gentle,
non-invasive procedure without any known side effects.
Dental hypnosis can without a doubt be used successfully. But
although numerous studies looked at neuronal brain correlates in
healthy subjects under hypnosis investigated by fMRI, PET and
Fig. 4. Neural activation patterns of dental phobic patients in the ACC (top), insula (middle) and hippocampus (down) for dental fearful stimuli (PS > NS) before (left) and after
hypnosis (right) (preFEAR > postFEAR). PS phobic stimuli, NS neutral stimuli.
8U. Halsband, T.G. Wolf / Journal of Physiology - Paris xxx (2016) xxx–xxx
Please cite this article in press as: Halsband, U., Wolf, T.G. Functional changes in brain activity after hypnosis in patients with dental phobia. J. Physiol.
(2016), http://dx.doi.org/10.1016/j.jphysparis.2016.10.001
EEG (e.g. Faymonville et al., 2000; Halsband, 2006; Halsband et al.,
2009; Rainville et al., 1997) there is a lack of studies, until today,
that demonstrate plastic cerebral changes in phobic patients under
hypnosis. Therefore, the purpose of the present study was to pre-
sent dental phobics with a phobic stimulus and to observe brain
activity changes after a brief hypnotic invervention. The results
showed a significant reduction in the left amygdala. Whereas
strong left amygdala activity could be observed in subjects pre-
sented with phobic stimuli (dental treatment) (Caseras et al.,
2010a) during an awake state, there was no such activity under
hypnosis. This demonstrates the neuroscientific efficacy of dental
hypnosis. The amygdala, an almond-shaped core region in the
medial temporal part of the limbic system, plays a key role in
anxiety- related behavior. The amygdala regions are responsible
for emotional processing of memory contents and provide a con-
nection between the sensory information and vegetative-motoric
anxiety reactions. Fiddick reported in a review (Fiddick, 2011) that
an important model of anxiety disorders is provided in the amyg-
dala and associated structures. These structures are considered to
play a major role in the neuronal basis of fear conditioning. Fur-
thermore, a distinction between fear-provoking immediate and
anxiety-provoking potential threats with cingulate cortex (and
insular) processing potential threats and amygdala processing
immediate threats were described. The amygdala activates a fear
reaction through direct transmission (Phan et al., 2002). In spider
phobics, Straube et al. (2006) found increased activations in the
amygdala when presenting phobic stimulus material (spiders)
compared to neutral stimuli (mushrooms). The amygdala activa-
tions could be observed during an identification exercise (subjects
were to say whether an object was a spider or a mushroom) as well
as a distraction exercise (same stimulus material, but deciding
whether lines in a circle were parallel or not). The authors con-
cluded that the amygdala has an essential function in the uncon-
scious processing of phobic threats. After dental hypnosis, there
was no amygdala activity, but simultaneously new activity in fusi-
form gyrus. Pujol et al. (2009) found increased activations in the
amygdala in subjects with social anxiety during presentation of
emotional faces. At once the authors reported a modulating effect
of fusiform gyrus on the amygdala. Numerous studies establish
that fusiform gyrus has a considerable function in perception.
Thus, it plays a key part in recognition of faces (Tong et al., 1998;
Chen et al., 2009), colour vision (Lee et al., 2000), suggested colour
perception (Halsband et al., 2009) and in colour memory (Slotnick,
2009). These data suggest that hypnosis may reduce an automatic
fear response by the amygdala through a modulating effect of fusi-
form gyrus. This immediately leads to an increased processing of
the visual input.
Most recently, Tian et al. (2015) reported that social distress
was correlated with the subcortical volume of the left amygdala
and the cortical volume of the right orbitofrontal cortex. The amyg-
dala also plays a critical role in situations of learned helplessness.
Unsolvable anagrams have been used to induce learned helpless-
ness in humans. Schneider et al. (1962) studied cerebral blood flow
changes when subjects were presented such non-solvable ana-
grams. They reported an increase in cerebral blood flow in the
amygdala and mammillary bodies. There are similarities to the sit-
uation when a patient with dental phobia is confronted with the
dentist’s chair and his equipment: he feels helpless. Learned help-
lessness may remain specific to one particular situation-in this
case to the visit of the dentist- but at other times generalizes across
situations.
Robinson et al. (2016) showed recently, that in healthy subjects
attentional control can modulate activity within anxiety potenti-
ated amygdala-frontal coupling. We observed a corresponding
down regulation of circuit coupling although the threatening con-
text of the stimuli remained when instructing them to shift their
attention away from threatening emotional stimuli by the subjects.
Our results are in consensus with Robinson et al. (2016) that the
reduction of activity after hypnotic induction both in healthy sub-
jects and phobic patients may be explained by a shift of attention
away from the disgusting and threatening character of the dental
stimuli. The use of hypnosis as psychological intervention in dental
treatment shows that attentional control is able to modulate the
neural circuitry of anxiety and fear. While even thinking about pain
during viewing of images illustrating dental treatments has the
ability to provoke enhanced orbitofrontal cortex activation
(Scharmueller et al., 2015), Scharmueller et al. (2015) found that
healthy controls showed a more widespread and stronger connec-
tivity compared to dental phobics during fear of pain. In areas acti-
vated (ACC, amygdala, putamen, pallidum, caudate nucleus), the
authors concluded that the pattern might reflect successful emo-
tion regulation, which is missing in phobic patients. However,
patients showed a link between caudate nucleus and orbitofrontal
cortex, what may be interpreted as a neural correlate of associating
pain with dental treatment (Scharmueller et al., 2015). Meier et al.
(2014) showed that despite equal painful dental stimuli, unequal
fear response was the result. It could be shown that painful dental
stimuli resulted in an increased susceptibility to fear conditioning.
When comparing to equally perceived stimuli applied to other
body sites, fear-related neurobiological mechanisms demonstrated
a superior condition ability of tooth pain (Meier et al., 2014). Also,
most recently, Jiang et al. (2016) used fMRI to investigate activity
and functional connectivity under hypnosis among three brain net-
works: the executive control network, the default mode network,
and the salience network. In their study guided hypnosis sessions
were used that were structurally similar to those that a hypnother-
apist might use to treat anxiety or pain. The authors reported in
highly hypnotizable subjects three specific changes:
1. A decrease in activity in the dorsal anterior cingulate, generally
associated with the salience network. It was argued that this is
a function of the narrowed attention when in hypnosis.
2. An increase in connections between the dorsolateral prefrontal
cortex and the insula. The authors concluded that this finding
reflects a brain-body connection that helps the brain process
and control physical experiences.
3. A decrease in connections between the dorsolateral prefrontal
cortex and the default mode network including the medial pre-
frontal and posterior cingulate cortex. Findings suggest this rep-
resents the disconnect between someone’s actions and their
awareness of their action – being in a so-called ‘‘flow state”.
Taken together these findings argue for plasticity changes in
the ACC and insula in our CO due to an altered state of attention
under hypnosis and a modified body awareness.
The insula is typically coactivated together with the amygdala
(Kohn et al., 2014; Robinson et al., 2010) especially during emotion
processing (Stein et al., 2007). Therefore it is not surprising that we
found a significant insular activation. It has been shown that in
healthy subjects increased insular activity is associated with anxi-
ety (Carlson and Mujica-Parodi, 2010; Stein et al., 2007; Caseras
et al., 2010a, 2010b). The studies by Baur et al. (2013) gave evi-
dence for a particular correlation of insula-amygdala connectivity
with state anxiety. The insula has also been shown to be involved
in processing stimuli evoking disgust as an emotional response and
in the representation of interoceptive information (Chen et al.,
2009). In cases where processing of disgust has often been reported
(Phillips et al., 1997; Calder et al., 2001), an important a role for
emotion processing of this brain area has been reported rarely
(Phan et al., 2002). The findings of Damasio et al. (2000) showed
that the insula activity is part of a central circuit with the monitor-
ing of ongoing internal emotional states. Our results demonstrate
U. Halsband, T.G. Wolf / Journal of Physiology - Paris xxx (2016) xxx–xxx 9
Please cite this article in press as: Halsband, U., Wolf, T.G. Functional changes in brain activity after hypnosis in patients with dental phobia. J. Physiol.
(2016), http://dx.doi.org/10.1016/j.jphysparis.2016.10.001
similar responses such as processing of the emotion of disgust dur-
ing awake condition and a reduced bilateral activation under hyp-
nosis in the insula.
The ACC plays an essential role in motivation, initiation and
goal directed behaviors (Devinsky et al., 1995). This means that it
produces a modulation or regulation among motor control, sensory
perception and cognition related to emotional, motivational and
attentional changes. Under hypnosis the ACC activity can be mod-
ulated (Rainville et al., 1997; Faymonville et al., 2000) The ACC is
specifically correlated with the reduction of pain perception
(Faymonville et al., 2006). Our findings show that during hypnosis
in healthy subjects as well as in dental phobics a reduction of the
ACC activity could be observed. This confirms the expectation that
the ACC may mediate the nociception during hypnotic state
(Faymonville et al., 2000).
All three anatomical structures discussed so far, i.e. the amyg-
dala, insula and ACC, form a crucial part of the so-called ‘‘anxiety
circuit” put forth by Etkin and Wager (2007). More recently,
Bruehl et al. (2014) confirmed the hyperactivation of the fear cir-
cuit. The authors provided a comprehensive update and meta-
analysis of neuroimaging studies on social anxiety disorders and
reported about additional hyperactivation in the medial parietal
and occipital regions.
We also found brain activity changes in the hippocampus. This
is not surprising because DP patients often report about traumatic
memories connected with an earlier visit to a dentist. Also, most
healthy subjects can recall some unpleasant memories connected
with a dental treatment. Even though the function of an important
memory structure, the hippocampus, including the surrounding
regions, has been proven for declarative knowledge (Bechara
et al., 1995), human recall memory (Merkow et al., 2015) and
recognition memory (Eichenbaum et al., 2007), its precise role in
recognition memory is still under discussion (Sauvage et al.,
2008; Wixted and Squire, 2011). In light of the theory that the hip-
pocampus is mainly responsible for recollection (Sauvage et al.,
2008; Yonelinas and Jacoby, 2012), we suppose that our results
in hippocampal activity in both healthy subjects and dental pho-
bics during visual and auditory stimuli of dental treatments can
be traced to a triggering of traumatic or unpleasant recollections
associated with previous dental treatments. In the present study,
we were able to demonstrate a significant reduction in hippocam-
pal activity during hypnosis in DP as well as no activation in CO
compared to conditions during an awake state. In DP the hip-
pocampal activation during the awake state was more pronounced
on the right side. This is in agreement with DP ´comments on
reporting about mental images about previous negative experi-
ences of dental visits rather than verbal memory rehearsal. Our
results are not in agreement with the findings by Lueken et al.
(2011a). The authors reported in a well-designed study about dis-
tinct neural mechanisms in dental phobia as compared to snake
phobia in the awake state. In snake phobics the fear circuitry struc-
tures were activated when subjects were presented with the pho-
bic stimulus material including the ACC, insula, amygdala and
thalamus. In contrast, in DP the authors reported an absence of
activation in these structures within the fear-circuit, but instead
DP activated prefrontal and lateral orbitofrontal areas. Similar to
our study only 12 subjects with dental phobia were tested. The fol-
lowing reasons may explain the differences in our results with the
previous study by Lueken et al. (2011a):
1. The video material used was different from our study. For
instance, Lueken et al. (2011a) showed a video when a dentist
puts on his latex gloves to prepare for the treatment. In con-
trast, in our study we used combined visual and auditory input
and only stimuli which were ranked in a previous investigation
(Halsband, 2011; Strickner and Halsband, 2010) to be most
frightening/disgusting (like drilling and extracting a tooth)
were included in the present investigation. This could have
resulted in a stronger phobic reaction in our subjects.
2. Patients may vary in their severity of their phobic reactions.
3. Regarding the small sample size in both studies one has to
acknowledge that in general the studies were underpowered
which may result in difficulties to detect smaller scale effects.
In other words, the choice of an experimental paradigm with
weaker fearful stimuli in combination with the small sample
size may have lead to subthreshold amygdala and insula.
4. Lueken et al. (2011a) utilized DP as a subgroup of the blood-
injection-injury phobia (B-I-I). However, recent evidence (van
Houtem et al., 2014) suggests that DP and B-I-I are independent
subtypes and patients with B-I-I may react differently from DP.
Further studies with a larger sample of DP patients are needed
to clarify the discrepancy between the two studies. There is also a
need of differentiating the fear circuitry-processes across different
phobic disorders. With reference to the study by Lueken et al.
(2011a) and to our own study one ought to systematically analyze
the activation patterns in patients with B-I-I as compared to DP
according to the criteria put forth by van Houtem et al., (2014) in
coherent comprehensive studies with a larger group of patients.
A number of limitations in our study should be considered.
First, all subjects were included on the basis of high hypnotic sus-
ceptibility. It needs to be examined whether subjects with low sus-
ceptibility scores would also benefit from a dental hypnotic
intervention and whether findings also apply to other treatment-
seeking patients. Second, the amount of participants tested was
relatively small what might limit a possible detections of small
scale effects. Third, although in our preliminary investigations we
carefully tested the parameters when planning this study, we can-
not exclude the possibility that e.g. subjective ranking of the stim-
uli in terms of adversiveness can be generalized to all DP subjects.
There may be large individual differences in responsiveness among
them. Fourth, it needs to be examined whether our significant
effects of hypnosis in reducing neural activity patterns in DP can
be generalized to other phobic patient groups.
Furthermore, it must be considered that neuroendocrine and
subjective stress reactions may influence the resulting functional
activation patterns (Muehlhan et al., 2011).
We ascertained that individual hypnosis is helpful for hypnotic
intervention instead of a standardized hypnotic induction from a
tape. In individual hypnosis key words (e.g. ‘‘sun”, ‘‘beach” and
‘‘sea”) can be chosen. These individual key words are strongly asso-
ciated with a relaxing state and can be used for an effective hypno-
sis in multisensory modalities (Wolf et al., 2016a, 2016b). More
data are needed regarding functional and structural connectivity
in dental phobia to identify the neural patterns underlying the sub-
type of this disorder and for approaches under hypnosis.
In summary, we showed that anxiety-provoking stimuli such as
undergoing dental surgery or endodontic treatments as well as
insufficient anaesthetics, which can trigger fear, can be effectively
reduced under hypnosis and provide benefits to healthy subjects as
well as to dental phobics. The present study gives scientific evi-
dence that hypnosis is a powerful and successful method for
inhibiting the reaction of the fear circuitry structures and recall
of unpleasant memory experiences.
Acknowledgements
The study was supported by the German branch of the Milton
H. Erickson Society of Clinical Hypnosis (M.E.G.), the German Soci-
ety of Dental Hypnosis (Deutsche Gesellschaft fuer Zahnaerztliche
Hypnose, DGZH) and the German Society of Hypnosis (Deutsche
Gesellschaft fuer Hypnose, DGH). We would like to express our
10 U. Halsband, T.G. Wolf / Journal of Physiology - Paris xxx (2016) xxx–xxx
Please cite this article in press as: Halsband, U., Wolf, T.G. Functional changes in brain activity after hypnosis in patients with dental phobia. J. Physiol.
(2016), http://dx.doi.org/10.1016/j.jphysparis.2016.10.001
thanks to Dr. Vesna Marcovici-Decker for the dental hypnotic
induction. We are grateful to Prof. Dr. Horst Urbach, medical direc-
tor of the Clinic for Neuroradiology at the University Hospital of
Freiburg, for the possibility to use the fMRI scanner. We would also
like to thank our research students for their practical assistance in
this project, Maximilian Wertz (PhD candidate) and Marion Jacob
for their help in producing our figures and tables and Dr. Arun
D’Souza for his assistance in the fMRI data analysis.
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