Proceedings of The Physiological Society

Future Physiology (Leeds, UK) (2017) Proc Physiol Soc 39, PC66

Poster Communications

Physiological mechanisms associated with the analgesic effect of visual feedback techniques

P. Wittkopf1, M. I. Johnson1

1. School of Clinical and Applied Sciences, Leeds Beckett University, Leeds, United Kingdom.

  • Figure 1. Mirror visual feedback (left). Virtual reality (right).

  • Figure 2. Mechanisms involved with motor control.

The use of visual feedback techniques in the rehabilitation of painful conditions have shown promising results in recent years. Visual feedback techniques include the use of mirrors and virtual reality (Figure 1). Mirrors are most commonly used in clinical practice. During mirror visual feedback the painful limb is hidden behind a mirror and the non-painful limb is placed in front of the mirror to create a reflection of a healthy-looking limb in the same position as the painful limb. Systematic reviews indicate that mirror visual feedback is effective for pain reduction when used as a course of treatment (Boesch et al., 2016) and in patients with complex regional pain syndrome (Thieme et al., 2016). The exact mechanism involved in the analgesic effect of visual feedback techniques is not fully elucidated. The aim of this presentation is to highlight the possible physiological mechanisms involved in the analgesic effect of visual feedback techniques. It has been suggested that pain relief associated with visual feedback techniques results from manipulation of sensory and motor integration within the central nervous system (Ramachandran et al., 1995).During movement, sensory information is used to compare intention with performance and motor commands are updated to adjust for discrepancies, ensuring movement matches intention (Figure 2). Motor signals associated with intended movement are not only sent to muscles but also to higher centres within the brain, as an efference copy, to prepare for the consequence of the motor output and to compare with sensory information arising from actual movement. It has been suggested that some painful conditions can be mediated by incongruence of sensory and motor information. Visual feedback techniques provide corrective sensory feedback to restore congruence between motor output and sensory input (McCabe & Blake, 2007). It has also been suggested that visual feedback techniques correct disrupted mental representations of body parts by reducing dysfunctional cortical reorganisation (Foell et al., 2014). Mental representations of affected limbs have been modified using mirrors to create the illusion of having two healthy moving limbs to alleviate phantom limb pain (Foell et al., 2014) and lenses to minify the view of hands that feel large in complex regional pain syndrome (Boesch et al., 2016). Foell et al. (2014) investigated the use of mirror visual feedback for phantom limb pain and found that the reduction in severity of pain was correlated with a reduction of dysfunctional reorganisation in the somatosensory cortex. In conclusion, Visual feedback techniques are promising therapeutic resources in the rehabilitation of painful conditions. However, more studies investigating the physiological mechanisms are needed. Specifically imaging studies will help to understand the neural processing of visual feedback techniques.

Where applicable, experiments conform with Society ethical requirements