Exploring cross-modal processing between vision and touch in virtual mirror therapy for use in phantom limb pain rehabilitation

  • Dion Willis

Student thesis: Doctoral Thesis

Abstract

Phantom Limb Pain (PLP) is a neuropathic condition that affects people suffering from deafferentation and amputation. Virtual Mirror Therapy (VMT) shows to be promising treatment however there are under-researched areas. The reintroduction of tactile sensation to the phantom limb has been suggested to ameliorate phantom limb pain. However, delivering a tactile sensation to a phantom limb is difficult. Current studies utilise a specific neurological adaptation which is not ubiquitous across all amputees, limiting its viability. Therefore, the aim of this thesis is to investigate factors that may improve relocation of a tactile sensation to another location. This uses principles of virtual mirror therapy and the rubber hand illusion, with an emphasis on measuring relocation alongside the quality of experience. Three studies were conducted to achieve this aim.
The first study investigated whether a sense of embodiment could be created with reduced agency. A new way of viewing proprioceptive drift was devised and the results shows that moving the virtual environment’s background could influence a persons proprioception in a predicable way. In addition to this finding, a by product of the methodology showed that 30% of participants perceived an illusionary tactile perception when a virtual object collided with the participants’ virtual limb.
The second study investigates a way of measuring tactile relocation of a physical vibration sensation. Principles of sensory integration are used from the rubber hand
illusion and provide a foundation for relocating a tactile sensation. A novel method for localising tactile sensation on a virtual arm was devised, which provided quantitative information regarding the amount of tactile displacement. This study offers contradictory evidence that an innocuous visual stimulus can relocate a physical, tactile sensation laterally to the opposite limb as seen in other VMT applications. However, sensory integration was observed, providing evidence that the underlying principle was demonstrated.
The third study, investigates whether accumulated exposure to a distal visual stimulus could relocate a tactile sensation to a greater extent than seen in study 2. Findings show a repeated, structured exposure, has a small impact on the extent a visual capture can be relocated to a distal location. Additionally, a structured presentation of the visual stimuli can help to better retain an accurate tactile localisation of a tactile sensation when the visual stimulus is no longer spatially coupled with it.
Overall, this thesis has developed a more comprehensive and empirical understanding of the principles used in both the rubber hand illusion and VMT to relocate tactile sensation and how they both can be used in conjunction with a clinical outcome in mind.
Date of AwardMay 2022
Original languageEnglish
SupervisorBrett Stevens (Supervisor) & Vaughan Powell (Supervisor)

Cite this

'