Abstract
It has been suggested that a proprioceptive deficit may exist in Parkinson's disease (PD); however proprioception has not been studied in those who experience freezing of gait (FOG). Proprioception was investigated through stimulation of proprioceptive receptors via patellar tendon vibration. In a force matching task to either 10% or 30% MVC, response to vibration with and without vision of a force target was compared between 15 PD with FOG (PD FOG), 15 PD without FOG (PD non FOG), and 15 non-PD control participants (Controls). In a 15-second trial, vision of the target was provided for the first 10 seconds but in the last 5 seconds, four conditions were possible: i) vision, no vibration; ii) vision, vibration; iii) no vision, no vibration; or iv) no vision, vibration. The expected healthy response to vibration was an overshoot of the target. With vibration, a non-significant overshoot was found in Controls and no response was found in PD non FOG. When vision was removed, neither Controls nor PD non FOG significantly undershot the target. Interestingly, in the PD FOG group, undershooting was found with both the addition of vibration (F(2,42)=5.27,p<0.01) and removal of vision (F(2,42)=5.23,p<0.01), suggesting that a higher-level deficit of sensorimotor integration is associated with FOG. In spite of PD being an asymmetrical disease, undershooting was seen (with vibration) in both limbs, thus a central mechanism appears to be responsible for the proprioceptive deficit in PD.
