Tactile remapping beyond space.

Reacting to a touch on the skin often requires the remapping of the initial somatotopicaly-based representation of the stimulus into an external frame of reference that incorporates information about current body posture. A growing number of studies support the view that tactile encoding in external coordinates occurs automatically. However, it remains unclear whether or not spatial task demands are required to trigger this remapping process, casting some doubt on the automaticity hypothesis. We designed three experiments in which space was progressively removed, and tactile remapping across different body postures was gauged through the modulation of visual performance. We used speeded two-alternative forced-choice colour judgements (i.e., a nonspatial selection feature) about visual targets presented laterally following a spatially noninformative (congruent or incongruent) tactile cue on one hand. In experiment 1, using footpedal responses, visual performance was modulated according to the external location of the tactile cue, regardless of hand posture (either crossed or uncrossed). In experiment 2, using verbal responses, external cueing was also observed (albeit in an attenuated fashion) despite the removal of space from response set. In experiment 3 we removed spatial uncertainty about cue and target locations by presenting tactile cues and visual targets from fixed positions, yet spatial congruency still exerted some modulation on visual performance, again independent of hand posture. These results demonstrate that engaging in spatial tasks is not a prerequisite for triggering tactile remapping, and are thus in agreement with previous accounts suggesting that touch is automatically remapped.