Radial trunk-centred reference frame in haptic perception

Lucile Dupin,Vincent Hayward,Mark Wexler

doi:10.1038/s41598-018-32002-3

Abstract

The shape of objects is typically identified through active touch. The accrual of spatial information by the hand over time requires the continuous integration of tactile and movement information. Sensory inputs arising from one single sensory source gives rise to an infinite number of possible touched locations in space. This observation raises the question of the determination of a common reference frame that might be employed by humans to resolve spatial ambiguity. Here, we employ a paradigm where observers reconstruct the spatial attributes of a triangle from tactile inputs applied to a stationary hand correlated with the voluntary movements of the other hand. We varied the orientation of the hands with respect to one another and to the trunk, and tested three distinct hypotheses regarding a reference frame used for integration: a hand-centred, a trunk-centred or an allocentric reference frame. The results indicated strongly that the integration of movement information and tactile inputs was performed in a radial trunk-centred reference frame.

Highlights

The shape of objects is typically identified through active touch
Even if the tactile inputs that are locally retrieved from an object can be quite informative about the whole object, for instance through local curvature[1] or surface orientation[2], this information is rarely sufficient to enable the perception of shape since the region of skin contact is typically much smaller than the object itself
We address the question of the reference frame in which haptic perception resulting from the integration of movement and sensory inputs may be represented

Summary

Introduction

The shape of objects is typically identified through active touch. The accrual of spatial information by the hand over time requires the continuous integration of tactile and movement information. Sensory inputs arising from one single sensory source gives rise to an infinite number of possible touched locations in space This observation raises the question of the determination of a common reference frame that might be employed by humans to resolve spatial ambiguity. These deviations may be seen as resulting from a combination of egocentric—relative to an observer’s body—and allocentric—external or absolute—reference frames[5] In these studies the orientation of the hand influenced the patterns of deviations[11,12], suggesting that haptic space might be represented in a combination of allocentric and hand-centred reference frames[13]. Movement[21,22], motor[23], or proprioceptive[24,25] information were found to contribute to length and distance perception, and so did arm-hand configurations[11,26] and www.nature.com/scientificreports/

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