Moving in an environment of induced sensory-motor incongruence does not influence pain sensitivity in healthy volunteers: A randomised within-subject cross-over experiment

A mismatch between the brain\u27s motor control and sensory systems has been suggested as one mechanism whereby maladaptive neuroplastic changes contribute to the experience of chronic pain. Several studies have investigated this hypothesis by artificially inducing a state of sensory-motor incongruence using mirrors. The data to date appear to suggest that creating an environment of sensori-motor incongruence induces various sensory changes and feeling of peculiarity, however the effect on pain is less clear. The aim of this study was to test the hypothesis that healthy participants would demonstrate reduced pain thresholds and report greater intensity of pain in a condition of induced sensory motor incongruence compared to conditions that did not promote incongruence

Moving in an environment of induced sensorimotor incongruence does not influence pain sensitivity in healthy volunteers: A randomised within-subject experiment

Objectives: It has been proposed that in the same way that conflict between vestibular and visual inputs leads to motion sickness, conflict between motor commands and sensory information associated with these commands may contribute to some chronic pain states. Attempts to test this hypothesis by artificially inducing a state of sensorimotor incongruence and assessing self-reported pain have yielded equivocal results. To help clarify the effect sensorimotor incongruence has on pain we investigated the effect of moving in an environment of induced incongruence on pressure pain thresholds (PPT) and the pain experienced immediately on completion of PPT testing. Methods: Thirty-five healthy subjects performed synchronous and asynchronous upper-limb movements with and without mirror visual feedback in random order. We measured PPT over the elbow and the pain evoked by testing. Generalised linear mixed-models were performed for each outcome. Condition (four levels) and baseline values for each outcome were within-subject factors. Results: There was no effect of condition on PPT (p = 0.887) or pressure-evoked pain (p = 0.771). A sensitivity analysis using only the first PPT measure after each condition confirmed the result (p = 0.867). Discussion: Inducing a state of movement related sensorimotor incongruence in the upper-limb of healthy volunteers does not influence PPT, nor the pain evoked by testing. We found no evidence that sensorimotor incongruence upregulates the nociceptive system in healthy volunteer

Mean differences and 95%CI for each outcome measure.

<p>Effect sizes are given for the experimental condition (asynchronous mirror) in comparison to each control condition.</p

Mean (SD) of each outcome measure across each condition (after adjusting for baseline values).

<p>PPT  =  Pressure pain threshold</p><p>NRS  =  Numerical rating scale</p

Mean (SD) of each outcome measure across each condition (after adjusting for baseline values).

<p>PPT  =  Pressure pain threshold</p><p>NRS  =  Numerical rating scale</p

Experimental set up.

<p><b>A</b>: asynchronous movements with mirror. <b>B</b>: synchronous movements with mirror. <b>C</b>: asynchronous movements without mirror. <b>D</b>: synchronous movements without mirror.</p