Pain Generated by Observation of Others in Pain
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PAIN GENERATED BY OBSERVATION OF OTHERS IN PAIN BY JODY OSBORN A thesis submitted to The University of Birmingham For the degree of DOCTOR OF PHILOSOPHY School of Psychology University of Birmingham May 2011 University of Birmingham Research Archive e-theses repository This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder. Acknowledgements Special thanks to Mr Grenville Green for funding the project and giving me this opportunity. Thank you so much to Dr. Stuart Derbyshire for giving me a chance as well as the support and guidance throughout my PhD. A million thanks to some great friends who helped me so much during my PhD; Alex, Fran, Nina, Christine, Noreen, Emma, Ben and Helen. Nicola, you have been the greatest. I don‘t know what I would have done without you! Abstract Recently, observation of pain has been linked to areas of the brain coding the sensory/discriminative aspects of pain (Avenanti et al., 2005; Avenanti et al., 2006). The experiential qualities associated with observing another in pain are poorly understood. In this thesis, we demonstrate that pain generated by observation of others in pain is reported by a significant minority of healthy individuals. The pain reported is mild, transient and occurs in the same location as the observed pain. Ten pain responders were matched with ten non-responders to take part in an fMRI study observing others in pain. Responders activated emotional and sensory brain regions associated with pain while the non- responders activated very little. Reports of pain were more likely to be accompanied by a pain memory. Pain responders are quicker to represent the perspective of others and have a more flexible sense of body ownership but are not more likely to report somatic symptoms during incongruent sensori-motor feedback. These findings provide convincing evidence that some people can readily experience pain during observation of others‘ pain. It is plausible that the mechanism underpinning pain reports evoked by observation of pain is not specific to pain processing per se. CONTENTS CHAPTER ONE: INTRODUCTION ............................................................................................. 1 1.1 Introduction ............................................................................................................................... 2 1.2 Models of Pain ........................................................................................................................... 3 1.2.1 Specificity Theory ............................................................................................................... 3 1.3 Brain regions implicated in affect and sensory aspects pain ..................................................... 6 1.4 Functional Pain .......................................................................................................................... 7 1.4.1 Prevalence of functional pain.............................................................................................. 7 1.4.2 The problem of functional pain........................................................................................... 8 1.4.3 Functional Pain and mental health ...................................................................................... 9 1.5 Bridging the gap between psychological and physical pain .................................................... 10 1.6 Generating pain sensation without external noxious stimuli ................................................... 11 1.6.1 Sensori—motor conflict .................................................................................................... 11 1.7. Acute Pain Symptoms with no obvious cause ........................................................................ 15 1.7.1 Mass Psychogenic Illness ................................................................................................. 15 1.8 Shared somatic experiences ..................................................................................................... 17 1.8.1 The development of somatic symptoms ........................................................................... 17 1.8.2 Affect and symptom reporting .......................................................................................... 18 1.9 Response expectancy and pain without injury ........................................................................ 19 1.10 Affect and observation of others in pain ............................................................................... 20 1.10.1 Embodied simulation ...................................................................................................... 20 1.11 Sensations and observing other in pain ................................................................................. 21 1.12 Touch Synaesthesia ............................................................................................................... 22 1.12.1 Synaesthesia and Pain ..................................................................................................... 23 1.13 Case studies of pain in the absence of injury ........................................................................ 25 1.13.1 Pain Flashbacks ............................................................................................................... 25 1.13.2 Watching another in pain generates pain sensation ........................................................ 26 1.14 Thesis Summary .................................................................................................................... 26 CHAPTER TWO: PAIN SENSATION GENERATED BY OBSERVATION OF OTHERS IN PAIN ......................................................................................................................................... 28 2.1 Introduction ............................................................................................................................. 28 2.2 Method ..................................................................................................................................... 30 2.2.1 Participants ........................................................................................................................ 30 2.2.3 Procedure .......................................................................................................................... 34 2.2.3.1 Visual Analogue Scales .............................................................................................. 34 2.2.3.3 The short version of the McGill Pain Questionnaire (Melzack, 1987) ...................... 35 2.3 Results ..................................................................................................................................... 35 2.3.1 Pain Reports ...................................................................................................................... 35 2.3.2 Somatisation ...................................................................................................................... 37 2.4 Discussion ................................................................................................................................ 38 2.5 Experiment Two ...................................................................................................................... 43 2.6 Introduction ............................................................................................................................. 43 2.6.1 Pain Judgements ............................................................................................................... 43 2.6.2 Memory for painful events and observation of pain ......................................................... 45 2.7 Method ..................................................................................................................................... 46 2.7.1 Design ............................................................................................................................... 46 2.7.2 Participants ........................................................................................................................ 46 2.7.3 Procedure .......................................................................................................................... 47 2.8 Results ..................................................................................................................................... 47 2.8.1 Pain Judgments ................................................................................................................. 48 2.8.2 Response Expectancy........................................................................................................ 50 2.8.3 Pain Memories .................................................................................................................. 50 2.9 Discussion ................................................................................................................................ 51 2.9.1 Empathy and Pain Judgements ........................................................................................