title: A supramodal representation of the body surface.
abstract: The ability to accurately localize both tactile and painful sensations on the body is one of the most important functions of the somatosensory system. Most accounts of localization refer to the systematic spatial relation between skin receptors and cortical neurons. The topographic organization of somatosensory neurons in the brain provides a map of the sensory surface. However, systematic distortions in perceptual localization tasks suggest that localizing a somatosensory stimulus involves more than simply identifying specific active neural populations within a somatotopic map. Thus, perceptual localization may depend on both afferent inputs and other unknown factors. In four experiments, we investigated whether localization biases vary according to the specific skin regions and subset of afferent fibers stimulated. We represented localization errors as a 'perceptual map' of skin locations. We compared the perceptual maps of stimuli that activate Aβ (innocuous touch), Aδ (pinprick pain), and C fibers (non-painful heat) on both the hairy and glabrous skin of the left hand. Perceptual maps exhibited systematic distortions that strongly depended on the skin region stimulated. We found systematic distal and radial (i.e., towards the thumb) biases in localization of touch, pain, and heat on the hand dorsum. A less consistent proximal bias was found on the palm. These distortions were independent of the population of afferent fibers stimulated, and also independent of the response modality used to report localization. We argue that these biases are likely to have a central origin, and result from a supramodal representation of the body surface.
authors.affiliation: Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, United Kingdom; Department of Psychology, University of Milano-Bicocca, Milano 20126, Italy.
authors.forename: Flavia
authors.initials: F
authors.lastname: Mancini
authors.affiliation: Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, United Kingdom; Department of Psychological Sciences, Birkbeck, University of London, London WC1E 7HX, United Kingdom.
authors.forename: Matthew R
authors.initials: MR
authors.lastname: Longo
authors.affiliation: Department of Neuroscience, Physiology, and Pharmacology, University College London, London WC1E 6BT, United Kingdom.
authors.forename: Gian Domenico
authors.initials: GD
authors.lastname: Iannetti
authors.affiliation: Institute of Cognitive Neuroscience, University College London, London WC1N 3AR, United Kingdom. Electronic address: p.haggard@ucl.ac.uk.
authors.forename: Patrick
authors.initials: P
authors.lastname: Haggard
mesh_terms: D000293:Adolescent; D000328:Adult; D000344:Afferent Pathways / Q000502:physiology; D001931:Brain Mapping; D005260:Female; D006225:Hand / Q000294:innervation; D006801:Humans; D008297:Male; D008875:Middle Aged; D008954:Models, Biological; D010812:Physical Stimulation; D012867:Skin / Q000294:innervation*; D013003:Somatosensory Cortex / Q000502:physiology*; D014110:Touch / Q000502:physiology*; D055815:Young Adult