Tactile remapping beyond space

Abstract

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.

Integration of anatomical and external response mappings explains crossing effects in tactile localization: A probabilistic modeling approach

“…In the present study, task instructions were phrased in anatomical terms (that is, participants were always asked to respond with the stimulated hand, and the side of space was not mentioned). Yet, as in previous studies, the external reference frame of touch had a remarkable influence on tactile task performance, supporting the view that the remapping of touch into external space is an automatic process (Kitazawa, 2002;Röder et al, 2004;Azañón et al, 2010a). However, a small variation of the task instructions (TOJ vs. FTL) altered the size of the crossing effect in spite of identical physical stimulation and required processing steps.…”

“…Yet, to plan actions toward the object, its location must be transformed into another, posture-dependent reference frame (Pouget et al, 2002;Sober & Sabes, 2005). Any perceived tactile stimulus seems to be transformed into an external-spatial reference frame (Driver & Spence, 1998;Yamamoto & Kitazawa, 2001a;Shore et al, 2002;Spence et al, 2004;Soto-Faraco et al, 2004;Röder et al, 2004;Schicke & Röder, 2006;Heed & Azañón, 2014;Heed et al, 2015), even when such recoding is currently not required (Kitazawa, 2002;Azañón et al, 2010a). This process of coordinate transformation is addressed as tactile remapping (Driver & Spence, 1998) and has been associated with regions of the intraparietal sulcus in posterior parietal cortex (Azañón et al, 2010b;Bolognini & Maravita, 2007;Renzi et al, 2013).…”

A three-dimensional spatial characterization of the crossed-hands deficit

“…In such instances, the order of two stimuli might be correctly computed, but it is inaccurately reported because of the incorrect localization of the stimuli in space (Badde, Heed, & Röder, 2016;Overvliet, Azañón, & Soto-Faraco, 2011;Roberts & Humphreys, 2008). This result has been interpreted as evidence that posture is taken into account automatically, even if it impairs task performance (Azañón, Camacho, & Soto-Faraco, 2010;Kitazawa, 2002;Yamamoto & Kitazawa, 2001). In the remapping literature, this idea has been extrapolated indirectly to all postures, to the extent that it is generally assumed that tactile remapping (or the encoding of touch in external space) is a general step in tactile processing (Azañón & Soto-Faraco, 2008;Kitazawa, 2002;Overvliet et al, 2011;Röder et al, 2004).…”

Hands behind your back: effects of arm posture on tactile attention in the space behind the body

“…It is now known that changes in body posture are taken into account automatically (e.g. Azañón and Soto-Faraco 2008;Azañón et al 2010a) because the representation of our body in space is constantly being updated by structures such as posterior parietal cortex (e.g. Bolognini and Maravita 2007;Azañón et al 2010b).…”