The sight of uncrossed rubber hands improves crossed-hands tactile order judgments

Elena Azañón, Parc Científic de Barcelona – Universitat de Barcelona

The representation of tactile event requires the engagement and coordination of different sensory systems utilizing disparate spatial frames of reference. Localization errors can arise as a consequence of incongruences between these reference frames, as when the observer crosses the hands across the body midline. In this posture, the perceived order of two tactile events applied quickly to different hands is often reversed. However, the way in which this spatial remapping between reference frames is carried out, and the kind of information relevant for this crossmodal organization of tactile space is still largely unknown. To help answer these questions, we attempted to modulate the crossed-hands deficit by way of visual capture of touch using rubber-hands. Participants judged the temporal order of two successive tactile events presented at their unseen hands which were either in crossed or uncrossed posture, while they watched a pair of rubber hands that were placed either in a crossed or uncrossed posture. The results showed a clear influence of available visual information about body posture in their tactile performance, suggesting a role of immediate visual information during the spatial remapping processes of tactile localization. This effect depended critically on the degree to which the visual information about the rubber hands can be incorporated as part of one’s own body schema. The study also supports previous claims about the idea that the effect of the crossed-hands on tactile TOJ is due to a systematic reversal in timing arising from the failure of the remapping process itself, rather than just to mere confusion.

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