Assessing the perception of movements in subjects with chronic pain using altered virtual feedback

Abstract

Chronic pain is often associated with body perception disturbances, but these have generally been assessed under static conditions. The objective of this study was to use a “virtual mirror” that scaled visual movement feedback to assess body perception during active movement. This study was performed in military subjects with chronic non-specific low back pain (CNSLBP, n = 15) and military healthy control subjects (n = 15). Subjects performed a trunk flexion task in front of a large screen displaying a full-body virtual mirror-image (avatar) in real-time. Avatar trunk movements were scaled to appear greater, identical, or smaller than the subjects’ actual movements. After each trial, subjects had to decide whether the avatar's movements were “greater” or “smaller” than their own movements. Based on this two-alternative forced choice paradigm, a psychophysical curve was fitted to the data for each subject, and several metrics were derived from this curve. Groups displayed a similar ability to discriminate between different levels of movement scaling. Still, subjects with CNSLBP showed an abnormal performance and tended to overestimate their own movements (shifted psychophysical curve). These results extend previous work in patients with CNSLBP, and denote an important relationship between body perception, movement and pain. As such, the method developed in this study can offer new avenues for understanding and managing body perception disturbances and abnormal movement patterns in patients with pain. A similar method is currently being implemented for the assessment of perception of upper limb movements in individuals with complex regional pain syndrome. It could also potentially be extended to therapeutic applications, to help patients with kinesiophobia to overcome their fear of moving.