UNIVERSITY OF CALIFORNIA, SAN DIEGO How the Body Can Feel Wrong: Sensory Processing and Neural Body Representation in Transsexuality and Anorexia Nervosa A dissertation submitted in partial satisfaction of the requirements for the degree Doctor of Philosophy in Psychology and Cognitive Science by Laura Kristen Case Committee in charge: Professor Vilayanur S. Ramachandran, Chair Professor Nicholas Christenfeld Professor Eric Halgren Professor Walter Kaye Professor Amanda Roberts Professor John Serences 2013 Copyright Laura Kristen Case, 2013 All rights reserved. The Dissertation of Laura Kristen Case is approved, and is acceptable in quality and form for publication on microfilm and electronically: Chair University of California, San Diego 2013 iii DEDICATION I would like to dedicate this dissertation to my parents, who taught me to observe and question everything. To my dad, who studies the “unconscious” from a different angle, and to my mom, who always asks the hardest and most important questions. iv EPIGRAPH In most public and most scientific discussions, sex and nature are thought to be real, while gender and culture are seen as constructed. But these are false dichotomies. Anne Fausto-Sterling, Sexing the Body In a sense, when we look at the world, we are hallucinating all the time. One could almost regard perception as the act of choosing the one hallucination that best fits the incoming data. V S Ramachandran, The Tell-Tale Brain: A Neuroscientist's Quest for What Makes Us Human Never lose a holy curiosity. Albert Einstein v TABLE OF CONTENTS Signature Page ........................................................................................................................... iii Dedication ................................................................................................................................. iv Epigraph ..................................................................................................................................... v Table of Contents ....................................................................................................................... vi List of Figures........................................................................................................................... vii List of Tables .............................................................................................................................. x Acknowledgements .................................................................................................................... xi Vita ......................................................................................................................................... xiii Abstract .................................................................................................................................. xvii Introduction ................................................................................................................................ 1 Chapter 1: Skin Conductance Response to Somatosensation from Body Parts that Feel Congruent or Incongruent with Gender ..................................................................................... 10 Chapter 2: Magnetoencephalography Recording of Somatosensory Evoked Fields in Body Parts that Feel Congruent or Incongruent with Gender ..................................................... 25 Chapter 3: Diminished Size-Weight Illusion in Anorexia Nervosa: Evidence for Visuo- Proprioceptive Integration Deficit ............................................................................................. 76 Chapter 4: Magnetoencephalography Recording of Somatosensory Evoked Fields in Body Parts that Feel Dysphoric or Neutral in Individuals with Anorexia Nervosa ...................... 87 Chapter 5: Allocentric Body-Viewing: Effects on Body Size Estimation and Body Satisfaction in Patients with Eating Disorders.......................................................................... 116 Conclusion .............................................................................................................................. 136 vi LIST OF FIGURES Chapter 1 Figure 1.0: Average z-scored skin conductance response for breast and leg. TR and CIS participants were poked on the breast and leg with a Neurotip® while skin conductance was measured continuously. Left plot shows data for first ten trials at each body site and right plot shows data for trials 11-20 ...................... 21 Figure 1.1: Breast-Leg mean z-scored skin conductance response difference scores. TR and CIS participants were poked on the breast and leg with a Neurotip® while skin conductance was measured continuously. Breast-Leg difference score of average z-scored skin conductance responses for the first 10 trials at each body location are shown ..................................................................................................................................... 22 Chapter 2 Figure 2.0: Illustration of MEG somatosensory stimulation paradigm. White rectangles show placement of reflective tape where the participant was tapped ............. 57 Figure 2.1: Example averaged Sensory Evoked Field in sensor space after spatial filtering and trial rejection. Average waveforms from a chest block from (A) a TR participant and (B) a CIS participant ....................................................................... 58 Figure 2.2: FreeSurfer average brain displaying the regions of interest (ROIs) analyzed. A: lateral view of right hemisphere, (1) primary somatosensory cortex; (2); secondary somatosensory cortex; (3) superior parietal lobule; (4) IPS; (5) supramarginal gyrus; (6) posterior insula; (7) anterior insula. B: medial view of right hemisphere, (8) medial temporal lobe. ROIs drawn based on FreeSurfer atlas and observed functional activation ........................................................................ 59 Figure 2.3: Mean dSPM values for the Chest condition for the TR versus CIS groups at (A) 40ms; (B) 72ms in CIS group; (C) 140ms. Units of activation amplitude are arbitrary. Yellow: TR > CIS; Blue: CIS > TR. ....................................... 60 Figure 2.4: Averaged dSPM timecourses for the chest condition for each ROI .............. 61 Figure 2.5: Averaged dSPM timecourses for the hand condition for each ROI ............... 63 Figure 2.6: Figure from Di Noto et al., 2013. One version of the female hermunculus. Both versions position the female breast and nipple on primary somatosensory cortex in the same location as the male chest and nipple. ....................... 65 Figure 2.7: Figure from Stephan et al., 2006. The late component of the SEF to median nerve stimulation was found to be reduced in contralateral S2 in males, relative to females (and in the elderly, relative to young adults). ................................... 66 Figure 2.8: Figure from Tsakiris et al., 2010. Model of neural inference of body ownership. .................................................................................................................... 67 vii Chapter 3 Figure 3.0: Presentation of SWI disks. On SWI trials, the participant held a small-sized disk weighing 90 g and a large-sized disk weighing 90-210 g. The participant watched the disks at all times and generated estimates of the weight of each disk relative to the other ....................................................................................... 79 Figure 3.1: Log of SWI ratios by trial type in AN patients and healthy controls. Higher small to large disk size-weight ratios indicate greater illusion of perceiving the smaller disk as heavier when it actually was not. The higher the log size-weight ratio from the actual log weight ratio of the disks (dashed line), the greater the illusion perceived .................................................................................. 81 Figure 3.2: Log of SWI ratios in AN patients and healthy controls. AN patients and healthy controls estimated the weights of small disk and large disk pairs or varying relative weights. Visual information about disk size creates a “size- weight illusion” that the smaller disk is heavier than it actually is. Estimated weight ratios of the small to large disks were averaged and linearized using a log transform. Higher log size-weight values indicate greater illusion of perceiving the smaller disk as heavier when it actually was not ..................................................................................................................................... 79 Chapter 4 Figure 4.0: Body satisfaction ratings for overall body, hand, and abdomen. AN participants were significantly less satisfied with their body, hand, and abdomen than CON particpiants. They were also significantly more dissatisfied with their abdomen that with their hands, relative to the CON participants.................................. 104 Figure 4.1: Illustration of MEG somatosensory stimulation paradigm. White rectangles show placement of reflective tape where the participant was tapped ........... 105 Figure 4.2: Example averaged Sensory Evoked Field in sensor space after spatial filtering and trial rejection. Average waveforms from an abdomen block from (A) an AN participant and (B) a CON participant ....................................................... 106 Figure 4.3: Mean dSPM values for the abdomen condition for the AN versus CON groups at (A) 40ms; (B) 72ms in CIS group; (C) 140ms. Units of activation amplitude are arbitrary. Yellow: AN > CON; Blue: CON > AN ................