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Exp Brain Res (2015) 233:351358 DOI 10.1007/s00221-014-4118-3
RESEARCH ARTICLE
Visual detail about the body modulates tactile localisation biases
Aaron N. Margolis Matthew R. Longo
Abstract The localisation of tactile stimuli requires the integration of visual and somatosensory inputs within an internal representation of the body surface and is prone to consistent bias. Joints may play a role in segmenting such internal body representations, and may therefore inuence tactile localisation biases, although the nature of this inuence remains unclear. Here, we investigate the relationship between conceptual knowledge of joint locations and tactile localisation biases on the hand. In one task, participants localised tactile stimuli applied to the dorsum of their hand. A distal localisation bias was observed in all participants, consistent with previous results. We also manipulated the availability of visual information during this task, to determine whether the absence of this information could account for the distal bias observed here and by Mancini et al. (Neuropsychologia 49:11941201, 2011). The observed distal bias increased in magnitude when visual information was restricted, without a corresponding decrease in precision. In a separate task, the same participants indicated, from memory, knuckle locations on a silhouette image of their hand. Analogous distal biases were also seen in the knuckle localisation task. The accuracy of conceptual joint knowledge was not correlated with tactile localisation bias magnitude, although a similarity in observed bias direction suggests that both tasks may rely on a common, higher-order body representation. These results also suggest that distortions of conceptual body representation may be more common in healthy individuals than previously thought.
Received: 4 March 2014 / Accepted: 28 September 2014 / Published online: 10 October 2014 Springer-Verlag Berlin Heidelberg 2014
Keywords Touch Tactile localisation
Body representation
Introduction
Localising tactile stimuli on the body surface typically relies on integrating somatosensory and visual information within a common frame of reference (Kennett et al. 2001). When access to visual information is restricted, and somatosensation relied upon to localise tactile stimuli, performance is both relatively imprecise (Harris et al. 2004;Moore and Schady 1995) and prone to systematic biases.For example, substantial constant errors of localisation have been reported on a variety of body parts, including the hand (Culver 1970; Mancini et al. 2011), forearm (Azan et al. 2010; Cholewiak and Collins 2003),...