A novel method for investigating the importance of visual feedback on somatosensation and bodily-self perception

Abstract

Abstract Aims Visual feedback is hypothesized to play an important role in the phantom limb condition. In this study we attempt to create an illusory experimental model of phantom limb wherein this condition is simulated by removing the visual input from the upper limb in a group of intact participants. The aim of the study is to investigate the role of visual feedback on somatosensation, nociception and bodily-self perception. Methods Using a novel mixed reality (MR) system, the visual feedback of the left hand is removed in order to visually simulate a left hand amputation on 30 healthy participants (15 females). Using a within-subject design, three conditions are created: visual amputation condition (MR with no visual input); visual condition (MR with normal vision); and a baseline condition (no MR). Thermal detection and nociceptive thresholds using method of limits are measured. Proprioception of the visually amputated hand is investigated by probing the felt hand position on a proximal-distal axis from the body. Using a questionnaire the effects of the missing visual feedback on bodily self is assessed. Results There was a clear drift in proprioception of the left hand in the proximal direction between the control and visual amputation condition (p <0.001). A decrease in cold detection was also significant between the control and visual amputation condition (p < 0.001). Finally, questions on perceptual experiences indicated that the observed proprioceptive retraction of the visually amputated hand was also felt by the participants. Conclusions Missing visual feedback greatly influences the perception of the visually amputated arm underlining the importance of visual feedback. The observed proprioceptive retraction of the hand resembles the telescoping perceptions often reported by phantom limb patients. The novel method developed for this study, is a new tool to investigate the influence of visual feedback on the relationship of bodily-self and chronic pain.