Virtual environment benefits motor dysfunction in Functional Neurological Disorder: Evidence from Virtual and Augmented Reality

Background: Virtual and Augmented Reality (VR/AR) are increasingly used in medicine and may offer novel interventions for Functional Neurological Disorder (FND) by targeting mechanisms of impaired motor control. However, evidence for the effect of different modalities on movement in FND is limited. Moreover, it is hypothesized that visual feedback of one s affected arm could reinforce FND symptoms through maladaptive self-monitoring. The present study aims to compare motor performance under visual feedback of a virtual avatar versus the real arm. Methods: Fifteen FND patients and eighteen healthy controls completed a dual motor reaching task (touching a virtual fruit such as orange or apple appearing in front of them) with a virtual headset across three modalities: Augmented Reality (AR), where participants saw their real arm; Virtual Reality (VR), with a virtual arm; and Virtual Reality Improved (VRI), with artificially enhanced straightness and larger collision zone with the target. Their movement speed, straightness and number of velocity peaks were calculated for each fruit catch. Additionally, the number of collisions between the eyes and the body was calculated with eye tracking technology. Results: FND participants were slower and produced less smooth movements in AR compared to VR (b = 1.09, z = 8.83, P < .001) and VRI (b = 0.85, z = 6.91, P < .001), while the opposite effect was found in healthy controls. Eye tracking showed that FND patients looked more at their affected hand than unaffected hand (b = -1.46, SE = 0.34, z = -4.23, p < .001; OR = 0.23). Conclusions: Virtual feedback of their limbs avatar appears to support better motor performance, while visual feedback of their real limb appears to exacerbate motor impairments in FND patients, likely reinforcing maladaptive self-monitoring. These findings highlight the therapeutic potential of VR interventions and provide the basis for future studies examining longer protocols, clinical outcome and potential implementation in standard motor rehabilitation.