Seeing and identifying with a virtual body decreases pain perception.
ABSTRACT Pain and the conscious mind (or the self) are experienced in our body. Both are intimately linked to the subjective quality of conscious experience. Here, we used virtual reality technology and visuo-tactile conflicts in healthy subjects to test whether experimentally induced changes of bodily self-consciousness (self-location; self-identification) lead to changes in pain perception. We found that visuo-tactile stroking of a virtual body but not of a control object led to increased pressure pain thresholds and self-location. This increase was not modulated by the synchrony of stroking as predicted based on earlier work. This differed for self-identification where we found as predicted that synchrony of stroking increased self-identification with the virtual body (but not a control object), and positively correlated with an increase in pain thresholds. We discuss the functional mechanisms of self-identification, self-location, and the visual perception of human bodies with respect to pain perception.
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ABSTRACT: Accumulating evidence shows that manipulations of cortical body representation, for example, by simply viewing one's own body, can relieve pain in healthy subjects. Despite the widespread use of the rubber hand illusion (RHI) as an effective experimental tool for the manipulation of bodily awareness, previous studies examining the analgesic effect of the RHI have produced conflicting results. We used noxious heat stimuli to induce finger pain in 29 healthy subjects, and we recorded the participants' pain thresholds and subjective pain ratings during the RHI and during the control conditions. Two control conditions were included in our experiment - a standard one with reduced illusion strength (asynchronous stroking control) and an additional one in which the participants viewed their own hand. Raw data showed that both the RHI and the vision of the own hand resulted in slightly higher pain thresholds than the asynchronous stroking control (illusion: 47.79 °C; own-hand: 47.99 °C; asynchronous: 47.52 °C). After logarithmic transformation to achieve normality, paired t-tests revealed that both increases in pain threshold were significant (illusion/asynchronous: p = 0.036; own-hand/asynchronous: p = 0.007). In contrast, there was no significant difference in pain threshold between the illusion and the own-hand conditions (p = 0.656). Pain rating scores were not log-normal, and Wilcoxon singed-rank tests found no significant differences in pain ratings between the study conditions. The RHI increases heat pain threshold and the analgesic effect of the RHI is comparable with that of seeing one's own hand. The latter finding may have clinical implications.European journal of pain (London, England) 03/2014; · 3.37 Impact Factor
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ABSTRACT: Experiencing tactile facial stimulation while seeing synchronous stimuli on the face of another individual induces 'enfacement', i.e. the subjective illusory experience of ownership of the other’s face (explicit measure) and the attribution of the others’ facial features to one’s own face (implicit measure). Here we expanded previous knowledge by investigating if the tendency to include the other into one’s own representation is influenced by positive or negative interpersonal attitudes derived either from consolidated socio-cultural stereotypes or from newly acquired, short-term individual interactions with a specific person. To this aim, we tested in Caucasian white participants the enfacement with a white and a black confederate, before and after an experimental procedure inducing a positive or negative perception of each of them. The results show that the subjective experience of enfacement with in- and out-group others before and after the manipulation is similar. The bias in attributing other’s facial features to one’s own face after synchronous stroking was, instead, dependent on whether the other person was positively perceived, independently of his/her ethnicity. Thus, we show that realistic positive face-to-face interactions are more effective than consolidated racial biases in influencing the strength of self-attribution of another persons’ facial features in the context of multisensory illusions. Results suggest that positive interpersonal interactions might powerfully change the plasticity of self-other representations. - See more at: http://journal.frontiersin.org/Journal/10.3389/fnbeh.2014.00102/abstract#sthash.pspGdxF7.dpufFrontiers in Behavioral Neuroscience 03/2014; · 4.76 Impact Factor
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ABSTRACT: Appropriate sensorimotor correlations can result in the illusion of ownership of exogenous body parts. Nevertheless, whether and how the illusion of owning a new body part affects human perception, and in particular pain detection, is still poorly investigated. Recent findings have shown that seeing one's own body is analgesic, but it is not known whether this effect is transferable to newly embodied, but exogenous, body parts. In recent years, results from our laboratory have demonstrated that a virtual body can be felt as one's own, provided realistic multisensory correlations. The current work aimed at investigating the impact of virtual body ownership on pain threshold. An immersive virtual environment allowed a first-person perspective of a virtual body that replaced the own. Passive movement of the index finger congruent with the movement of the virtual index finger was used in the 'synchronous' condition to induce ownership of the virtual arm. The pain threshold was tested by thermal stimulation under four conditions: (1) synchronous movements of the real and virtual fingers; (2) asynchronous movements; (3) seeing a virtual object instead of an arm; and (4) not seeing any limb in real world. Our results show that, independently of attentional and stimulus adaptation processes, the ownership of a virtual arm per se can significantly increase the thermal pain threshold. This finding may be relevant for the development and improvement of digital solutions for rehabilitation and pain treatment.European journal of pain (London, England) 01/2014; · 3.37 Impact Factor
Seeing and identifying with a virtual body decreases pain perception
Alexander Hänsela,⇑, Bigna Lenggenhagerb, Roland von Känela, Michele Curatoloc, Olaf Blankeb,d
aDivision of Psychosomatic Medicine, Department of General Internal Medicine, Inselspital, Bern University Hospital and University of Bern, Switzerland
bLaboratory of Cognitive Neuroscience, Ecole Polytechnique Fédérale de Lausanne, Station 19, 1015 Lausanne, Switzerland
cUniversity Department of Anaesthesiology and Pain Therapy, University Hospital of Bern, Inselspital, Bern, Switzerland
dDepartment of Neurology, University Hospital of Geneva, Geneva, Switzerland
a r t i c l e i n f o
Received 8 July 2010
Received in revised form 31 March 2011
Accepted 31 March 2011
Available online 12 May 2011
a b s t r a c t
Pain and the conscious mind (or the self) are experienced in our body. Both are intimately linked to
the subjective quality of conscious experience. Here, we used virtual reality technology and visuo-tac-
tile conflicts in healthy subjects to test whether experimentally induced changes of bodily self-con-
sciousness (self-location; self-identification) lead to changes in pain perception. We found that
visuo-tactile stroking of a virtual body but not of a control object led to increased pressure pain
thresholds and self-location. This increase was not modulated by the synchrony of stroking as pre-
dicted based on earlier work. This differed for self-identification where we found as predicted that syn-
chrony of stroking increased self-identification with the virtual body (but not a control object), and
positively correlated with an increase in pain thresholds. We discuss the functional mechanisms of
self-identification, self-location, and the visual perception of human bodies with respect to pain
? 2011 European Federation of International Association for the Study of Pain Chapters. Published by
Elsevier Ltd. All rights reserved.
The sensation of pain requires a subject or an ‘‘I’’ of conscious
experience – a ‘‘self’’ (Sartre, 1948). Self and pain share the loca-
tion where they are experienced. Humans normally experience
pain on the body surface or within their body. The self is nor-
mally also perceived within the bodily borders. Self-location (i.e.
the experience that the self is localized at a position in space;
normally within one’s bodily borders) and self-identification (i.e.
the feeling to be the owner of a body) are crucial elements of
self-consciousness. Self-location and self-identification can both
be clinically experimentally manipulated (Blanke and Metzinger,
Clinical neurology studies revealed that epilepsy, migraine, vas-
cular stroke, and electrical cortical stimulation may lead to changes
in self-location and self-identification during so-called out-of-body
and related experiences (OBE, Blanke et al., 2004; Irwin, 1985).
Further development of the seminal observations by George
Stratton made at the end of the 19th century, recently revealed
that OBE-like states can also be experimentally induced and stud-
ied in healthy individuals (Stratton, 1899). The exposition of partic-
ipants to conflicting multisensory (visuo-tactile) bodily cues using
mirrors (Altschuler and Ramachandran, 2007) or video devices
(Ehrsson, 2007; Lenggenhager et al., 2007; Mizumoto and
Ishikawa, 2005) induced illusory own body perceptions in healthy
participants. Altschuler and Ramachandran (2007) evoked in their
study the illusion of standing outside oneself by arranging two
opposing mirrors producing an image of the person standing
distantly to his or her actual location. While stroking one’s cheek
and looking at their distant reflection at the same time, the
participants reported that they had the feeling of touching
somebody else and not themselves.
In a study by Lenggenhager et al., a video camera was placed be-
hind the participant and relayed to a head-mounted display. In this
way, the subject sees his own body in front of him (Lenggenhager
et al., 2007). Tactile stimulation (stroking) was applied on the
participant’s back and the visual information related to this
stimulation was systematically manipulated by displaying it as
either synchronously or asynchronously (with a temporary delay)
on the virtual body. During synchronous stroking of the virtual
body, but not of a virtual control object, participants felt illusory
self-identification (as if the virtual body was their own) as well
as illusory self-location (as if they were localized at a position in
front of their body).
Here, we explored whether pain experience of increasingly ap-
plied pressure is altered during states of illusory self-location and
self-identification. We applied an extensively used and validated
experimental pain assessment to measure pressure pain threshold
(Curatolo et al., 2006). Based on earlier reports of people with OBE,
1090-3801/$36.00 ? 2011 European Federation of International Association for the Study of Pain Chapters. Published by Elsevier Ltd. All rights reserved.
⇑Corresponding author. Tel.: +41 31 6320249.
E-mail address: Alexander.Haensel@insel.ch (A. Hänsel).
European Journal of Pain 15 (2011) 874–879
Contents lists available at ScienceDirect
European Journal of Pain
journal homepage: www.EuropeanJournalPain.com
we hypothesized that participants’ pressure pain threshold would
increase during illusory self-location relative to baseline and in
comparison with control conditions (Green, 1968). We further
hypothesized that the magnitude of illusory self-location and
self-identification would correlate with the increase in pressure
2. Materials and methods
The study protocol was approved by the ethics committee of
the Canton of Bern. Each participant gave written informed con-
sent to the study protocol. We recruited 15 healthy volunteers
(eight females, mean age: 39 years, SD ±10) among employees
of the University Hospital of Bern, Switzerland. All participants
were blind to the study’s hypothesis. Exclusion criteria were any
clinically relevant somatic disease or mental disorder. Addition-
ally, only participants who reported no chronic pain disorder or
any other acute pain during the 2 weeks prior to testing were
included.We excluded participants
substances such as analgesics and antidepressants regularly in
the 2 weeks prior to testing. Vision was normal or corrected-to-
normal. Each participant received CHF 60 (approximately USD
50) as incentive.
2.2. Experimental set-up
A mannequin’s back or an object (square, white, human-sized
cardboard box) was filmed from behind at a distance of 2 m and
projected onto a video head-mounted display (HMD). Participants
saw either the mannequin’s back or the object via the HMD as if it
was standing in front of them (see Fig. 1). An experimenter stood
between the mannequin/object and the participant and stroked
the back of the participant and the mannequin/object simulta-
neously during 3 min at a frequency of approximately 0.5– Hz.
By using an electronic device to induce a time delay (800 ms) for
video projection, participants experienced the touch of the stroking
synchronously or asynchronously in comparison to the presented
mannequin/object’s stroking. There were thus four different condi-
tions: mannequin/synchronous (MS), mannequin/asynchronous
(MAS), object/synchronous (OS), and object/asynchronous (OAS).
Delayed video projection was used in asynchronous conditions.
Experimental conditions were randomized in a within-subject de-
sign. Therefore, the sequence of the four conditions differed for
Pain threshold measurements were performed by the same
investigator (M.C.) by using an electronic pressure algometer
(Somedic, Sweden) with a probe surface of 1 cm2. The investigator
was blinded to the experimental condition. A continuously increas-
ing pressure was applied at a rate of 30 kPa/s (kilopascal/s) to the
index finger of the participant’s left hand up to a maximum of
1000 kPa. Participants held a stop button in their right hand and
were instructed to press as soon as they perceived the pressure
as painful in order to determine the pain threshold. This procedure
was performed three to five times to get the participants ac-
quainted with the procedure of the algometer. Afterwards, three
measurements with 1 min intervals were performed and counted
as baseline measurements, before pain thresholds were measured
three times, beginning 1 min after induction of the experimental
condition and with 1 min intervals between the consecutive mea-
surements. The mean values of the three baseline measurements
and the three measurements under each experimental condition
were used for statistical analysis.
According to Lenggenhager et al., participants were asked to
close their eyes and perform small steps on spot after each exper-
imental condition (Lenggenhager et al., 2007). While stepping on
spot, an experimenter moved the participant’s body backwards
by ?1 m. Participants were then instructed to walk with closed
eyes to the position where they believed to were standing during
the experiment. The drift between the starting position and the fi-
nal position was measured in centimeters in the anterior–posterior
axis indicating experienced self-location.
We adapted an already used questionnaire to measure
self-identification (see Table 1, Botvinick and Cohen, 1998;
Lenggenhager et al., 2007). Quality of pain was measured by a
validated German version of the McGill pain questionnaire (see
Table 2, Radvila et al., 1987). Participants were asked to rate the
self-identification and pain questionnaires immediately after each
experimental condition on a 7-point Likert scale (1 = totally dis-
agree to 7 = totally agree). The rating of the questionnaires to-
gether with the setting up the HMD led to a break of ?4 min
between the experimental conditions.
We assessed participants’ expectation of change in pain-thresh-
old after having finished all four experimental conditions by asking
the question ‘‘I expect that the illusion of an abnormal self-location
Fig. 1. Experimental set-up: Participant sees through a video head-mounted display the mannequin’s back (A) or a noncorporeal object (B) standing in front of the participant
and is stroked synchronously or asynchronously with it.
A. Hänsel et al./European Journal of Pain 15 (2011) 874–879
leads to an increase in pressure pain threshold’’. This question was
also rated on a 7-point Likert scale: 1 = totally disagree, 7 = totally
2.4. Statistical analysis
Data were analyzed using SPSS statistical software package
(version 15.0). Level of significance was set at p < 0.05 (two-tailed).
Normal distribution of data was tested by the Kolmogorov–Smir-
nov test. Pain threshold and drift data showed a Gaussian distribu-
tion; therefore, we applied a 2 ? 2 repeated-measures ANOVA
(with the within factors Character (mannequin/object) and Strok-
ing (synchronous/asynchronous)) to analyze the change in drift
(measurement of self-location) and pain-threshold with the exper-
imental condition. Because questionnaire scores were not normally
distributed, we applied non-parametric Friedman ANOVAs for
dependent samples to test whether self-identification and quality
of pain measures would differ between the four experimental con-
ditions. Post hoc analysis applied Wilcoxon matched pair test to
identify differences between the individual experimental condi-
tions. Pearson correlation analysis was used to estimate the rela-
tionship between two normally distributed variables.
3.1. Pressure pain threshold
Mean baseline pressure pain threshold was 336.4 kPa (STE
±25.6 kPa). The 2 ? 2 repeated-measures ANOVA showed a signif-
icant main effect for Character (F(1, 14) = 7.23, p = 0.018) with in-
creased pain thresholds for the conditions where the mannequin
was shown (MS/MAS) compared to showing the object (OS/OAS).
There was neither a main effect for Synchrony (F(1, 14) = 1.12,
p = 0.31) nor an interaction effect between Character and Syn-
chrony (F(1, 14) = 0.76, p = 0.56). Fig. 2 illustrates the increase in
pain threshold as compared to baseline for each experimental
3.2. Self-location (drift)
The 2 ? 2 repeated-measures ANOVA showed a significant main
effect for Character (F(1, 14) = 0.84, p = 0.007). There were larger
drifts in the conditions that showed the mannequin (MS/MAS)
compared to the showing of the object (OS/OAS). There was no
main effect of Synchrony (F(1, 14) = 2.83, p = 0.11) nor an interac-
tion effect between Character and Synchrony (F(1, 14) = 2.41,
p = 0.14). Fig. 3 illustrates the drift for each experimental condition.
Mean differences between baseline pain threshold measurement and experimental setting and mean drift (±SE).
Repeated measures ANOVA p-value
Pain threshold (kPa) ± SE
Drift (cm) ± SE
56.1 ± 21.0
19.6 ± 5.9
36.3 ± 21.5
8.6 ± 3.1
12.4 ± 13.6
6.5 ± 4.4
6.8 ± 19.1
6.4 ± 5.3
Questions of the global-attribution questionnaire.
(1) It seemed as if I were feeling the touch of the highlighter in the location where I saw the body of the mannequin touched
(2) It seemed as though the touch I felt was caused by the highlighter touching body of the mannequin
(3) I felt as if the body of the mannequin was my body
(4) It felt as if my (real) body was drifting towards the front (towards the body of the mannequin)
(5) It seemed as if I might have more than one body
(6) It seemed as if the touch I was feeling came from somewhere between my own body and the body of the mannequin
(7) It appeared (visually) as if the body of the mannequin was drifting backwards (towards my body)
Fig. 2. Mean increases of pain thresholds (kPa) for the four experimental conditions
(±SE) as compared to baseline threshold: Mannequin/synchronous stroking, man-
nequin/asynchronous stroking, object/synchronous stroking, and object asynchro-
nous stroking (⁄p < 0.05).
Fig. 3. Mean drift (in cm) for the four experimental conditions (±SE): Mannequin/
synchronous stroking, mannequin/asynchronous stroking, object/synchronous
stroking, and object asynchronous stroking (⁄p < 0.05).
A. Hänsel et al./European Journal of Pain 15 (2011) 874–879
3.3. Self-identification questionnaire
A Friedman-ANOVA for nonparametrical data revealed a
significant effect for questions 1–3 (Table 1). Further analyses
(Wilcoxon matched pair test) for question 1 showed that for
both Characters the ratings were higher in the synchronous than
in the asynchronous condition (mannequin Z = 2.6, p = 0.01; ob-
ject Z = 2.8, p = 0.005), while the two synchronous conditions
and the two asynchronous conditions did not significantly differ
from each other. The same pattern was observed for question 2
(mannequin Z = 2.1, p = 0.04; object Z = 2.7, p = 0.008). For ques-
tion 3 (self-identification) a significant difference between syn-
chronous and asynchronous stroking was only revealed in the
mannequin condition (Z = 2.7, p = 0.008), but not in the object
3.4. Correlation between pressure pain threshold and self-
For question 3 (showing an interaction effect between object
and synchrony) we calculated a correlation between scores and
pain threshold. We used the difference between the synchronous
and asynchronous condition and performed this analysis sepa-
rately for the mannequin and the object condition.
We found a significant correlation between the difference in the
synchronous versus asynchronous ratings of question 3 and higher
pain threshold in the mannequin condition (r = 0.55, p = 0.03), but
not in the object condition.
The latter suggests that the more a participant self-identified in
the synchronous (as compared to the asynchronous) condition
with the mannequin the higher the pain threshold in the synchro-
nous compared to the asynchronous condition. There were no sig-
nificant correlations between scores of question 1 and 2 and
change in pain threshold for the mannequin and object conditions
(all p-values >0.41).
3.5. Pain questionnaire and participants’ expectations to study
Participants described the quality of pain during the measure-
ment of pressure pain threshold mainly as compressing, clamping
and dull. Participants perceived a minor-to-moderate intensity of
pain. Table 3 shows the five most intensely experienced pain qual-
ities for each condition.
On average, participants agreed to the principal study hypothe-
sis that abnormal self-location would lead to an increase in pain
threshold (Mean 5.3 ± 1.8). The extent of the participant’s agree-
ment to the study hypotheses did not significantly correlate with
changes in pain threshold and drift.
We found that visuo-tactile stroking of a virtual body but not of
a control object led to increased pressure pain thresholds. This in-
crease was not additionally modulated by the synchrony of strok-
ing (as we – based on previous work – expected (Aspell et al., 2009;
Lenggenhager et al., 2007, 2009). Changes in self-location mim-
icked these increases in pain threshold and revealed a main effect
of Character, but not of Stroking or an interaction between both
factors. This observation, however, differed for self-identification
which was measured by questionnaires. Our data also show that
the synchrony between visual and tactile stroking systematically
increased self-identification in the mannequin (or virtual body),
but not in the object condition. Additional correlation analysis
found that this increase in self-identification was associated with
an increase in pain threshold. To sum up, the present data show
two main findings: Firstly, seeing synchronous or asynchronous
stroking of a virtual body with respect to the application of tactile
stimulation to the back of one’s body are both associated with sig-
nificant increases in pain thresholds, which was not the case when
the touch was seen on a object. This finding confirms earlier obser-
vations that seeing a human body increases pain thresholds (see
Longo et al., 2009 for similar findings when seeing a body part).
The data additionally reveals that the magnitude of the perceived
strength of pain (being applied by pressure) is directly linked to
the magnitude of self-identification with a seen body, but not to
self-location (Lenggenhager et al., 2007).
Other research using the rubber hand illusion found changes in
skin conductance (recorded from the participants’ hand) when the
rubber hand was approached by potentially harmful or painful vi-
sual stimuli (Armel and Ramachandran, 2003; Ehrsson et al., 2007).
Comparable changes in skin conductance were also observed in an
illusion closely related to the full body illusion that was tested in
the present study (Ehrsson et al., 2007). Studying the link between
pain and the bodily self, it has also been reported that when upper-
limb amputees see their real arm/hand superimposed on the
amputated arm/hand in a mirror, they may report relief from
phantom pain (Maclachlan et al., 2006; Ramachandran and Rog-
ers-Ramachandran, 1996). Other studies reported a reduction of
phantom pain for amputees by controlling a virtual limb in immer-
sive virtual reality (Sato et al., 2010; Cole et al., 2009; Murray et al.,
2007) or a decrease of the skin temperature in the real hand during
the rubber hand illusion (Moseley et al., 2008a).
To the best of our knowledge, however, the perception of pain-
ful stimuli that are directly applied on the participants’ body has
not been previously investigated during the manipulation of the
bodily self. The present study tested this directly and reveals that
pain thresholds can be altered by manipulating multisensory
(visuo-tactile) bodily input. We also found an increase in pressure
pain thresholds during both body conditions that did not depend
on the synchrony of stroking. Although participants did not report
any differences in pain qualities during the different experimental
conditions, pain threshold increased by 16% from baseline in the
synchronous stroking condition. This effect can be considered as
clinically relevant. To compare our results, we have previously
found an increase of 17% in pain pressure tolerance threshold after
infusion of the potent opioid remifentanil at a target plasma con-
centration of 1 ng/ml, a dose which also resulted in detectable
sedation (Luginbühl et al., 2003). It might be possible that the
increase in pressure pain threshold was partly influenced by par-
ticipants’ expectations. As we did not measure participants’ expec-
tation before the measurements, but only at the end of the study,
one can argue that participants’ answers reflect their observation
rather than their expectation. Participants’ agreement of the
study’s hypothesis (i.e. abnormal self-location would lead to an in-
crease in pain threshold) did neither correlate with the induced
Five most common perceived pain descriptions for the four experimental conditions
on the McGill pain questionnaire (value of intensity: 1 = minor, 5 = intolerable).
1.3 +/? 1.5
A. Hänsel et al./European Journal of Pain 15 (2011) 874–879
changes in pain threshold nor the extent of changes in drift. This
indicates that the observed increase in pain threshold cannot be
explained by expectation alone. It can also be argued that the
application of noxious signals to the body may alter illusory self-
location per se. This is, however, not very likely, because studies
of the rubber hand illusion (RHI) paradigm on pain perception
showed that nociceptive visuo-tactile stroking induces changes in
hand ownership comparable to visuo-tactile stroking alone (Cape-
lari et al., 2009). Thus, applying noxious signals to the hand did not
inhibit the rubber hand illusion as also shown in the present study.
Why did self-location and pain threshold not show a significant
interaction between character and synchrony of stroking as pre-
dicted by us and as observed for self-location in our previous stud-
ies (Lenggenhager et al., 2007, 2009)? Our data on pain perception
may suggest that the bodily self – as tested here based on visuo-
tactile conflicts – influences pain perception differently than it
influences tactile perception (Aspell et al., 2009). This suggestion
is based on the present observation that pain thresholds were
not modulated by stroking and did not show a modulation that de-
pended on both experimental factors. Several mechanisms may ac-
count for this. Firstly, the co-application of painful stimulation may
– in addition to the tactile stroking – have altered the effects pre-
viously observed during synchronous and asynchronous visuo-tac-
tile stroking on the drift (self-location); this may also have affected
the modulation of pain perception, i.e. leading to a decrease of the
effects of synchrony and the interaction. Secondly, the application
of a painful stimulus may have led to a shift of attention towards
one’s own body and thus altering the manipulation due to the syn-
chrony of stroking on drift as well as on pain thresholds. This atten-
tional shift towards the own body (backward drift) may have
altered the generally found forward drift during synchronous ver-
sus asynchronous stimulation, although both conditions lead to a
forward drift. These mechanisms may counteract the selectivity
of illusory changes with respect to self-location as well as pain
thresholds. Furthermore the visuo-tactile delay varied between
the present and previous work (e.g. Lenggenhager et al., 2007).
Studies on visuo-tactile integration have also shown that the delay
of the visual and tactile stimulus is important for body representa-
tion and bodily self-consciousness (Aspell et al., 2009). Indepen-
dent from these technical aspects, it may be that the different
functional mechanisms between pain and tactile perception (as
tested in Aspell et al. (2009)) described at the neuroanatomical,
neurophysiological, and psychological level (i.e. Craig, 2002) may
lead to the observed differences. Future research is needed to
determine whether the observed results on pain reflect the above-
mentioned technical differences, attentional mechanisms, or re-
flect differences between pain and touch systems.
Despite these open questions, our data corroborate anecdotal
reports of altered pain perception during the experience of disem-
bodiment in healthy subjects and in patients with neurological dis-
ease. This may also be useful in order to develop novel behavioral
pain treatments (Röder et al., 2007). With respect to disembodi-
ment, it has been reported that people with OBE experience
changes in pain level and pain quality (Bünning and Blanke,
2005; Green, 1968; Irwin, 1985). These changes in pain experience
are associated with a wide range of pain characteristics and were
reported to involve the experienced intensity or quality as well
as the person’s attitude towards pain. These subjective changes –
that have not been subjected to quantitative analysis in previous
work – were mainly associated with a decrease in the intensity
of pain. The present data show that the strength of self-identifica-
tion with the virtual body positively correlated with the increase in
pain thresholds pointing to at least partly comparable mechanisms
in people with pain during OBE (Green, 1968). Changes in self-
identification (as quantified by question 3) depended on synchrony
and the shown object, leading – as predicted – to strongest changes
in the mannequin/synchronous condition, also correlated with
changes in pain thresholds. As changes in the present study in
self-location did not correlate with changes in pain thresholds,
we suggest that self-identification (or owning and identifying with
a body) rather than self-location (where we experience our body to
be) modulates humans’ experience of pain.
Finally, the small sample size of N = 15 is a limitation of the
present study. Due to lack of power the difference between thy
synchronous/asynchronous stroking condition with regard to
pain/drift may have not reached statistical significance. Although
the increase in pressure pain threshold and drift were highest in
the mannequin/synchronous stroking condition, this increase was
not strong enough to reach statistical significance. Greater statisti-
cal power might have revealed significant effects of synchrony. Fu-
ture research is necessary to elucidate the role of the different
mechanisms and its effects on self-location and pain thresholds.
A possible perspective that arises from our findings is the devel-
opment of therapeutic behavioral procedures as a clinical tool to
alleviate pain either alone or in combination with other pain treat-
ments (Raz and Shapiro, 2002; Röder et al., 2007). Moseley re-
ported an intriguing way to alleviate chronic pain perception by
using binoculars to create a multisensory conflict (Moseley et al.,
2008b). Patients with chronic arm pain watched their affected limb
using binoculars while performing a standardized repertoire of
hand movements. Thus, pain intensity as well as swelling of fingers
was decreased or increased when these patients watched their
limb through inverted binoculars that minimized or magnified
the size of limb.
Future studies need to evaluate whether changes in pain per-
ception following multisensory conflicts – as tested here – or in
other multisensory conditions may offer novel therapeutic inter-
ventions for chronic pain patients (Moseley, 2005, 2008).
Conflict of interest
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