Spatial remapping of tactile events

Abstract

During the apparently mindless act of localizing a tactile sensation our brain must realign its initial spatial representation on the skin (somatotopicaly arranged) according to current body posture (arising from proprioception, vision and even audition).^1-3 We have recently illustrated⁴ the temporal course of this recoding of tactile space from somatotopic to external coordinates using a crossmodal cueing psychophysical paradigm^5,6 where behavioural reactions to visual targets are evaluated as a function of the location of irrelevant tactile cues. We found that the tactile events are initially represented in terms of a fleeting, non-conscious but nevertheless behaviorally consequential somatotopic format, which is quickly replaced by the representations referred to external spatial locations that prevail in our everyday experience. In this addendum, we test the intuition that frequent changes in body posture will make it harder to update the spatial remapping system and thus, produce stronger psychophysical correlates of the initial somatotopically-based spatial representations. Contrary to this expectation, however, we found no evidence for a modulation when preventing adaptation to a body posture.

Acknowledgements

This research was supported by grants from the Spanish Ministerio de Educación y Ciencia (Spain; SEJ 2007-64103/PSIC and CDS00012) and by a fellowship Beca de Formación de Profesorado Universitario from the Spanish Ministerio de Educación y Ciencia to Elena Azañón.

Figures and Tables

Figure 1 Experimental results. Mean spatial cueing effects (opposite minus same-side trials reaction times) as a function of CTOA and posture change condition. A positive cueing effect indicates faster performance for visual events in the same-side trials as compared to the opposite-side trials, as coded with respect to positions in external space. Black lines/symbols represent the results in the blocked posture condition and grey lines/symbols in the interleaved postures condition. The results for the uncrossed-hands conditions are represented by solid lines/open symbols and the results of crossed-hands conditions are represented by dashed lines/filled symbols. The error bars denote the SEM (standard error of the mean).

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