The Accuracy and Stability of Body Representation

How we perceive our bodies and how the body is represented in the brain is not yet fully understood. We need accurate information about our bodies in order to interpret and react to sensory information that is constantly being received and that is coded relative to our body. My dissertation aims to understand how the body is perceived and represented in the brain by exploring the accuracy and stability of body representation. I developed a novel two-alternative forced choice adaptive staircase psychophysical method to determine how accurate people are in judging real and distorted life-size images of their body. Participants were sequentially shown two life-size images of their body (one interval containing the undistorted image and one interval containing the distorted image) and had to report which image most closely matched their own perception of their body size. Width and length dimensions were distorted separately. The image was also presented in different orientations (such as upright, right, left, and upside down) in order to assess how accuracy perception changes when the image is presented in familiar and unfamiliar views. Four separate experiments were conducted to test perceived size for: 1) the face, 2) the arm, 3) the hand, and 4) the full body. The goal of these studies was to measure accuracy in different orientations, for both the width and length dimensions, to obtain baseline values of how distorted the brains representation of various body parts are. I demonstrated that there are distortions in perceived size and that factors such as body part, orientation, sex, and body satisfaction impacted accuracy. To explore the nature and extent of the brains plasticity and flexibility, I investigated how manipulating body representation affects body perception and whether accuracy values can be changed. Manipulating body representation using both visual and vestibular methods resulted in changes to perceived body size accuracy. These results provide insights into how the brain represents the body, revealing that body size perception is flexible and plastic.