The vestibular system modulates the contributions of head and torso to egocentric spatial judgements

Elisa R Ferrè,Matthew R Longo,Patrick Haggard,Adrian J T Alsmith

doi:10.1007/s00221-021-06119-3

Abstract

Egocentric representations allow us to describe the external world as experienced from an individual’s bodily location. We recently developed a novel method of quantifying the weight given to different body parts in egocentric judgments (the Misalignment Paradigm). We found that both head and torso contribute to simple alter-egocentric spatial judgments. We hypothesised that artificial stimulation of the vestibular system would provide a head-related signal, which might affect the weighting given to the head in egocentric spatial judgments. Bipolar Galvanic Vestibular Stimulation (GVS) was applied during the Misalignment Paradigm. A Sham stimulation condition was also included to control for non-specific effects. Our data show that the weight given to the head was increased during left anodal and right cathodal GVS, compared to the opposite GVS polarity (right anodal and left cathodal GVS) and Sham stimulation. That is, the polarity of GVS, which preferentially activates vestibular areas in the right cerebral hemisphere, influenced the relative weightings of head and torso in egocentric spatial judgments.

Highlights

When describing our surroundings we may need to use expressions such as “on my left”, “on my right”, etc., to facilitate the hearer’s imagination of a scene, or mark an important contrast between the spatial relations of the speaker and the hearer relative to a common environment
We investigated whether a Galvanic Vestibular Stimulation induced bias on spatial egocentric judgments supports a dynamic sensory-driven egocentric representation
Our data showed that the weight given to the head in determining an object’s location was increased during left anodal and right cathodal Galvanic Vestibular Stimulation (GVS), compared to the opposite GVS polarity and Sham stimulation

Summary

Introduction

When describing our surroundings we may need to use expressions such as “on my left”, “on my right”, etc., to facilitate the hearer’s imagination of a scene, or mark an important contrast between the spatial relations of the speaker and the hearer relative to a common environment. Resource, the capacity for egocentric spatial representation. Egocentric representations describe the external world as experienced from an individual’s location, in a manner sensitive to how the individual’s body is disposed (Jeannerod and Biguer, 1987). The body is considered the point of origin of egocentric representations (Bermúdez 1998, 2005). Changes in body posture potentially dissociate reference frames anchored to different body parts. Different body parts may function as origins of the egocentric reference frame

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