Bodily pleasure and the self: Experimental, pharmacological and clinical studies on affective touch

198 Pages·2016·1.63 MB·English

Bodily pleasure and the self:
Experimental, pharmacological and clinical studies
on affective touch

Laura Crucianelli

Submitted to the University of Hertfordshire in partial fulfilment
of the requirements of the degree of Doctor of Philosophy

April 2016
Abstract
In the last decade, neuroscience and psychology alike have paid increasing attention to
the study of affective touch, which refers to the emotional and motivational facets of tactile
sensation. Some aspects of affective touch have been linked to a neurophysiologically
specialised system, namely the C tactile (CT) system. While the role of this system for
affiliation, social bonding and communication of emotions have been investigated, less is known
about the potential role of affective touch in the awareness of the body as our own, i.e. as
belonging to our psychological ‘self’.
This thesis attempted to contribute to the knowledge on affective touch and its relation
to body awareness, by exploring the potential role of this modality to the way we perceive and
make sense of our body as our own. Specifically, this work aimed to advance the current state of
knowledge by investigating: 1) the effect of affective touch on the sense of body ownership,
which is a fundamental aspect of body awareness; 2) the relation between interoceptive
modalities, originating both internally (i.e. cardiac awareness) and peripherally (i.e. affective
touch), and exteroception in body awareness; 3) the effect of intranasal oxytocin on the
perception of affective touch and bodily awareness; 4) the perception and social modulation of
affective touch in psychiatric patients who show difficulties in body awareness, namely patients
with Anorexia Nervosa, and 5) the modulating role of self-other distinction and of self-other
relation in the perception of affective touch and body awareness.
In a first experiment (N = 52) the rubber hand illusion paradigm was used to investigate
the role played by CT-optimal, affective touch in the sense of body ownership. The results
showed that slow, pleasant touch enhanced the experience of embodiment in comparison to
faster, neutral touch, suggesting that affective touch might uniquely contribute to the sense of
body ownership. The following study (N = 75), used a similar methodology to test whether
interoceptive sensitivity as measured by a heartbeat counting task would modulate the extent to
which affective touch influences the multisensory process taking place during the rubber hand
illusion. The results could not confirm a systematic relation between interoceptive sensitivity
and the perception of affective touch, nor its influence on body ownership. The next study (N =
41) included a double-blind, placebo-controlled, randomised, cross-over design testing the
effect of intranasal oxytocin on the perception of affective touch and body ownership, as
measured by means of the rubber hand illusion. There was no evidence supporting the
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hypothesis that intranasal oxytocin could influence the CT system as tested in this study. The
next study (N = 55) applied some of the above methodologies to investigate the perception of
CT-optimal touch in patients with anorexia nervosa and its emotional modulation by top-down
factors. The results confirmed the hypothesis that people with anorexia nervosa show a reduced
perception of affective touch compared to healthy controls, but its perception was not influenced
by top-down affective modulation, in the sense that both patients and healthy controls perceived
touch as more pleasant when presented concurrently with positive facial expressions compared
to neutral and negative faces. Finally, the last two studies (N = 76 and 35 healthy volunteers,
respectively) focused on the relationship between affective touch and body awareness in the
context of social cognition. These studies used both online and offline social modulation
paradigms to investigate the role of self-other distinction and of self-other relation in the
perception of affective touch. The results showed that positive top-down social information can
enhance the perceived pleasure of tactile stimulation.
Taken together, these studies point to the central role of affective touch in body
awareness and social cognition. Finally, they also pave the way for future studies examining the
role of disruptions of the CT system in the development of neuropsychiatric impairments of
body awareness and social cognition.

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Declarations
I declare that this thesis represents my own work and it has not previously been
submitted successfully for an award.

Aspects of Chapters 1, 2 and 5 are under review for publication in:
Gentsch, A., Crucianelli, L., Jenkinson, P., & Fotopoulou, A. (under review). The
Touched Self: Affective Touch and Body Awareness in Health and Disease. In H.
Olausson, J. Wessberg, I. Morrison, F. McGlone (Eds.), Affective Touch and the
Neurophysiology of CT Afferents. Springer.

The study presented in Chapter 2 has been published in:
Crucianelli, L., Metcalf, N.K., Fotopoulou, A., & Jenkisnon, P. (2013). Bodily pleasure
matters: Velocity of touch modulates body ownership during the rubber hand illusion.
Frontiers in Psychology, 4, 703

The study presented in Chapter 5 has been published in:
Crucianelli, L., Cardi, V., Treasure, J., Jenkinson, P., & Fotopoulou, A. (2016). The
perception of affective touch in Anorexia Nervosa. Psychiatry Research, 239, 72-78

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Acknowledgements
Words cannot entirely express how grateful I am to my principal supervisors, Dr
Katerina Fotopoulou and Dr Paul Jenkinson for providing the most wonderful scientific and
emotional support a PhD student could ever wish for. A big part of my “academic self” has
developed simply by observing their behavior and following their example. Thanks to Katerina
for believing in me from the first moment we met and for giving me amazing opportunities, and
to Paul; I will bring his kindness, transparency and positive attitude with me in everything I do.
Thanks both for their patience and for pushing me out of my comfort zone. Every time they
believed I could do something, I did.
I would like to express my special thanks to my supervisor, Dr Lucy Annett and Dr
Yannis Paoloyelis, Dr Lucy Serpell, Prof Janet Treasure and Dr Valentina Cardi for their
contribution to this thesis. Thanks to Noel Taylor, John Gill and Marcin Pacyna for their
technical support. I would also like to thank all the students who helped me with data collection,
in particular Nicola Metcalf; I am sure that what they gave to me will come back to them. I also
owe a huge thanks to the people I shared my PhD’s joys and tears with, even when physically
apart, Dr Charlotte Krahé and Dr Sahba Besharati. They made this experience so much more
rich, valuable and fun. And I know that, above all, I found two friends.
Heartfelt thanks to the people who became family and made London so enjoyable. First
and foremost, Valentina; she is my rock, my partner in crime and my travel companion. Andrea,
an endless source of joy and positive energy. Virginia and Saul, so much more than just
flatmates. Thanks to Roberta, who kindly showed me the way back to myself. And thanks to
Elena, May and Massimo for their special support and encouragement in the past few months.
To Ambra and Olga, thanks for being by my side sempre, comunque e ovunque.
I am forever grateful to my brother Luca and my parents, Eliana and Pietro, for their love and
support and for allowing me the freedom to choose who I wanted to be. Thanks for giving me
both ‘roots and wings’ and for letting me go without asking me when I would be back.

Finally, I would like to thank the University of Hertfordshire for funding this project and
a special thanks to all the participants to my studies for their time and availability.
This thesis would not have been possible without all of you. Grazie di cuore.
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Table of Contents
Abstract ........................................................................................................................................................... 1
Declarations .................................................................................................................................................... 3
Aknowledgments ............................................................................................................................................ 4
Table of Contents ............................................................................................................................................ 5
List of Tables ................................................................................................................................................ 10
List of Figures ............................................................................................................................................... 11
List of Appendices ...................................................................................................................................... 123
Abberviations ................................................................................................................................................ 13
Chapter 1: General introduction ............................................................................................................... 14
1.1. Background........................................................................................................................................... 14
1.2. A specialised pathway for affective touch: The C tactile system ......................................................... 16
1.3. Bodily pleasure: Affective touch as an interoceptive modality ............................................................ 18
1.4. Multisensory integration and bodily self-consciousness ...................................................................... 20
1.5. The role of interoception in body representation and the sense of body ownership ............................. 22
1.6. Role of others in the construction of the bodily self-consciousness ..................................................... 24
1.7. The neurobiological basis of affective touch ........................................................................................ 27
1.8. Aims and outline of this thesis.............................................................................................................. 29
Chapter 2: Bodily pleasure matters: Velocity of touch modulates body ownership during the rubber
hand illusion ............................................................................................................................................... 32
2.1. Introduction .......................................................................................................................................... 32
2.2. Materials and Method ........................................................................................................................... 35
2.2.1. Participants ................................................................................................................................. 35
2.2.2. Design and statistical analysis .................................................................................................... 35
2.2.3. Materials ..................................................................................................................................... 37
2.2.4. Procedure .................................................................................................................................... 38
2.3. Results .................................................................................................................................................. 39
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2.3.1. Pleasantness ratings .................................................................................................................... 39
2.3.2. Embodiment questionnaire – Composite Score of Ownership, Location and Agency ............ 39
2.3.3. Sub-component analysis ............................................................................................................. 41
2.3.4. Proprioceptive drift ..................................................................................................................... 43
2.4. Discussion .............................................................................................................................................. 43
2.5. Limitations and future directions ........................................................................................................... 45
Chapter 3: Integration of interoceptive and exteroceptive modalities during the Rubber Hand
Illusion: An experimental study on the sense of body ownership ........................................................... 47
3.1. Introduction .......................................................................................................................................... 47
3.2. Methods ................................................................................................................................................ 50
3.2.1. Participants ................................................................................................................................ 50
3.2.2. Design and Statistical analysis .................................................................................................. 51
3.2.3. Apparatus and Materials ............................................................................................................ 52
3.2.4. Experimental procedures ........................................................................................................... 53
3.3. Results .................................................................................................................................................. 55
3.3.1. Interoceptive sensitivity ............................................................................................................ 54
3.3.2. BMI and pre-RHI measures ...................................................................................................... 55
3.3.3. Rubber Hand Illusion ................................................................................................................ 56
3.3.4. Correlational analysis ................................................................................................................ 60
3.4. Discussion .............................................................................................................................................. 61
3.5. Limitations and future directions .......................................................................................................... 64
Chapter 4: The effect of oxytocin on the perception of affective touch and body awareness ............... 66
4.1. Introduction .......................................................................................................................................... 66
4.2. Methods ................................................................................................................................................ 73
4.2.1. Participants ................................................................................................................................ 73
4.2.2. Experimental design and statistical analysis ............................................................................. 74
4.2.3. Materials .................................................................................................................................... 78
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4.2.4. Procedure ................................................................................................................................... 80
4.3. Results .................................................................................................................................................. 82
4.3.1. Heartbeat baseline and interoceptive sensitivity ....................................................................... 82
4.3.2. Affective touch task ................................................................................................................... 82
4.3.3. Rubber hand illusion .................................................................................................................. 83
4.4. Discussion ............................................................................................................................................ 85
4.5. Other limitations ................................................................................................................................... 89
Chapter 5: The perception of affective touch in anorexia nervosa ........................................................ 90
5.1. Introduction .......................................................................................................................................... 90
5.2. Methods ................................................................................................................................................ 93
5.2.1. Participants ................................................................................................................................ 93
5.2.2. Design and data analysis ........................................................................................................... 94
5.2.3. Stimuli and apparatus ................................................................................................................ 95
5.2.4. Procedure ................................................................................................................................... 97
5.3. Results .................................................................................................................................................. 97
5.3.1. Demographics and mood ............................................................................................................ 97
5.3.2. Pleasantness ratings ................................................................................................................... 98
5.3.3. Correlations ............................................................................................................................. 100
5.4. Discussion .......................................................................................................................................... 101
5.5. Limitations and future directions ......................................................................................................... 104
Chapter 6: Look into the mirror: The effect of self vs. other-mirror observation on interoception 106
6.1. Introduction ........................................................................................................................................ 106
6.2. Methods .............................................................................................................................................. 111
6.2.1. Participants ............................................................................................................................... 111
6.2.2. Experimental design and statistical analysis ............................................................................ 112
6.2.3. Materials ................................................................................................................................... 113
6.2.4. Experimental procedure .......................................................................................................... 114
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6.3. Results .................................................................................................................................................. 115
6.3.1. Interoceptive sensitivity ............................................................................................................ 115
6.3.2. Pleasant touch ........................................................................................................................... 116
6.3.3. Correlational analysis .............................................................................................................. 118
6.4. Discussion ............................................................................................................................................ 118
6.5. Limitations and future directions ......................................................................................................... 121
Chapter 7: The effect of shared touch on bodily pleasure .................................................................... 123
7.1. Introduction ........................................................................................................................................ 123
7.2. Materials and methods ........................................................................................................................ 128
7.2.1. Participants ............................................................................................................................... 128
7.2.2. Experimental design and statistical analysis ............................................................................ 128
7.2.3. Control procedure ..................................................................................................................... 130
7.2.4. Materials and set-up ................................................................................................................ 131
7.2.5. Procedure ................................................................................................................................. 132
7.3. Results .................................................................................................................................................. 133
7.3.1. Pleasantness ratings .................................................................................................................. 133
7.3.2. Control embodiment questionnaire ........................................................................................... 135
7.4. Discussion ............................................................................................................................................ 136
7.5. Limitations and future directions ......................................................................................................... 138
Chapter 8: General discussion ................................................................................................................ 140
8.1. Introduction .......................................................................................................................................... 140
8.2. Summary of the main findings ............................................................................................................. 141
8.3. Methodological discussion ................................................................................................................... 145
8.3.1. Affective touch task .................................................................................................................. 145
8.3.2. Rubber hand illusion ................................................................................................................. 148
8.3.3. Heartbeat detection task ............................................................................................................ 149
8.3.4. Social modulation: facial expressions, mirror observation and synchronous experiences ....... 151
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8.4. The role of affective touch in the representtaion of the bodily self .................................................... 152
8.5. Integration of interoceptive and exteroceptive signals in bodily self-consciousness .......................... 155
8.6. A neurobiological basis for interoceptive bodily signals .................................................................... 159
8.7. The social modulation of bodily pleasure ........................................................................................... 161
8.8. Conclusion .......................................................................................................................................... 165
References ................................................................................................................................................... 167
Appendices .................................................................................................................................................. 191

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