Phantom limb phenomena: The unity of self and body

Abstract

Most amputees continue to experience an amputated body part as a phantom. This curious phenomenon partially relates to maintained presence of the limb in body representations, self-attribution to the missing limb and, occasionally, embodied sense of unity with the prosthesis. The aim of this thesis, comprising three sections, was to explore the corporeal perceptions of phantom limb phenomena, their relation to body representations, and process underlying self-attribution. First, questionnaire data were collected from 283 amputees to investigate the corporeal qualities of the phantom, and to systematically investigate how the phantom differs according to factors associated with amputation (Section 1, Chapters 2 to 10). These investigations gave an insight to the somatic experience of the phantom (e.g. phantom limb size, shape, posture and movement). The experience of somatosensory memories in the phantom, phantom triggers and the relationship between phantom pain and phantom limb movement were investigated. Further, striking parallels between phantom pain and restless legs syndrome were identified and discussed. Second, the experience of a unitary self with the phantom was investigated using a visual-capture illusion paradigm (Section 2, Chapters 11 to 14). Sense of ownership of a rubber or real hand was induced when participants observed a mirror reflection of the hand being touched or moved with stimulus objects. This study found that stimulation of the participant's congruent hand (i.e. the phantom hand in amputee participants) was not necessary to induce a sense of ownership, and embodiment of the seen hand. Embodiment illusions were heightened during perceived threat, with evasive motor responses being elicited to threatening stimuli, and more recent amputees experienced the most elaborate and intense illusory sensations.