Additional visual information on postural control mechanisms in Parkinson's disease: a pilot study

BACKGROUND: Individuals with Parkinson’s disease (PD) have sensorimotor deficits that affect the mechanisms of postural control. Additional visual information effects on postural control mechanisms in PD were unknown. AIM: To examine the effects of visual information on postural control mechanisms in individuals with PD. METHOD: Seven individuals with PD and five healthy adults (controls) stood, as quiet as possible, on a force plate for 35 seconds with eyes open, eyes closed, or with additional visual feedback [VF] of the center of pressure (COP). The COP trajectories were calculated in anterior-posterior and mediolateral directions and then decomposed to assess two postural control mechanisms: Rambling (i.e., supraspinal) and Trembling (i.e., peripheral). The amplitude and velocity of COP and Rambling and Trembling components were compared between groups for each visual condition. RESULTS: The amplitude and velocity of COP and its components were greater in individuals with PD than controls. They increased under closed eyes condition for PD group, but only the Rambling velocity increased in anterior-posterior direction for controls. When additional VF of the COP was provided, individuals with PD presented increased COP and Trembling velocity in mediolateral direction, while healthy individuals presented reduced sway in both directions. CONCLUSION: Individuals with PD showed greater postural sway and were more affected without visual information than controls. They were not able to use the additional VF to reduce their postural sway as healthy individuals due to changes in sensory integration, causing possible overload in supraspinal processes and compensatory effects in the peripheral postural control mechanisms.