Article

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 Abeta (innocuous touch), Adelta (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.
CI - Copyright (c) 2011 Elsevier Ltd. All rights reserved.

Langue : ANGLAIS