title: Mental body representations retain homuncular shape distortions: Evidence from Weber's illusion.
abstract: Mental body representations underlying tactile perception do not accurately reflect the body's true morphology. For example, perceived tactile distance is dependent on both the body part being touched and the stimulus orientation, a phenomenon called Weber's illusion. These findings suggest the presence of size and shape distortions, respectively. However, whereas each morphological feature is typically measured in isolation, a complete morphological characterization requires the concurrent measurement of both size and shape. We did so in three experiments, manipulating both the stimulated body parts (hand; forearm) and stimulus orientation while requiring participants to make tactile distance judgments. We found that the forearm was significantly more distorted than the hand lengthwise but not widthwise. Effects of stimulus orientation are thought to reflect receptive field anisotropies in primary somatosensory cortex. The results of the present study therefore suggest that mental body representations retain homuncular shape distortions that characterize early stages of somatosensory processing.
authors.affiliation: Department of Cognitive Science, University of California, San Diego, USA; Kavli Institute for Brain and Mind, University of California, San Diego, USA. Electronic address: lumiller@ucsd.edu.
authors.forename: Luke E
authors.initials: LE
authors.lastname: Miller
authors.affiliation: Department of Psychological Sciences, Birkbeck, University of London, United Kingdom.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Longo
authors.affiliation: Department of Cognitive Science, University of California, San Diego, USA; Kavli Institute for Brain and Mind, University of California, San Diego, USA.
authors.forename: Ayse P
authors.initials: AP
authors.lastname: Saygin
mesh_terms: D000328:Adult; D001828:Body Image; D004215:Distance Perception / Q000502:physiology*; D005260:Female; D005542:Forearm / Q000502:physiology; D006225:Hand / Q000502:physiology; D006801:Humans; D007088:Illusions / Q000502:physiology*; D008297:Male; D055698:Touch Perception / Q000502:physiology*; D055815:Young Adult
keywords: Body representation; Perception; Psychophysics; Somatosensory; Touch