The Role of the Environment in Eliciting Phantom-Like Sensations in Non-Amputees

Elizabeth Lewis,Martin J. Farrell,Donna M. Lloyd

doi:10.3389/fpsyg.2012.00600

Abstract

Following the amputation of a limb, many amputees report that they can still vividly perceive its presence despite conscious knowledge that it is not physically there. However, our ability to probe the mental representation of this experience is limited by the intractable and often distressing pain associated with amputation. Here, we present a method for eliciting phantom-like experiences in non-amputees using a variation of the rubber hand illusion in which a finger has been removed from the rubber hand. An interpretative phenomenological analysis revealed that the structure of this experience shares a wide range of sensory attributes with subjective reports of phantom limb experience. For example, when the space where the ring finger should have been on the rubber hand was stroked, 93% of participants (i.e., 28/30) reported the vivid presence of a finger that they could not see and a total of 57% (16/28) of participants who felt that the finger was present reported one or more additional sensory qualities such as tingling or numbness (25%; 7/28) and alteration in the perceived size of the finger (50%; 14/28). These experiences indicate the adaptability of body experience and share some characteristics of the way that phantom limbs are described. Participants attributed changes to the shape and size of their “missing” finger to the way in which the experimenter mimed stroking in the area occupied by the missing finger. This alteration of body perception is similar to the phenomenon of telescoping experienced by people with phantom limbs and suggests that our sense of embodiment not only depends on internal body representations but on perceptual information coming from peripersonal space.

Highlights

The sense of one’s own body is largely determined by the multisensory integration of visual, tactile, proprioceptive, and kinesthetic information
Given that the rubber hand illusion (RHI) and phantom limbs both result from the alteration of the sensory input that creates the sense of embodiment, the goal of the present paper was, firstly, to determine whether an analog of the phantom limb experience could be created in participants without an amputation through a variation of the RHI
The ability to create an analog of the phantom limb experience in intact participants could, prove to be an important tool in investigating the sense of embodiment and how it relies upon our interaction with the environment

Summary

Introduction

The sense of one’s own body is largely determined by the multisensory integration of visual, tactile, proprioceptive, and kinesthetic (and possibly auditory) information. Though we are aware of the resulting sense of embodiment, we are not normally aware of the multisensory integration that produces it This is only revealed in abnormal situations, such as body illusions, of which the rubber hand illusion (RHI; Botvinick and Cohen, 1998) is a striking example, and pathological phenomena, such as the experience of phantom limbs. Embodiment has been the subject of a wealth studies investigating normal body representation (e.g., Botvinick and Cohen, 1998; Armel and Ramachandran, 2003), only a handful of studies have sought to understand the phenomenological aspects and determinants of subjective experience underlying abnormal body representations, such as phantom limbs. The ability to create an analog of the phantom limb experience in intact participants could, prove to be an important tool in investigating the sense of embodiment and how it relies upon our interaction with the environment

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