March 2012
Martens KA, Almeida QJ
Although Parkinson's disease (PD) is traditionally considered a motor
output disorder, recent evidence suggests that people with PD may have
sensory and perceptual impairments that may underlie movement
impairments. Yet there has not been any direct testing of perceptual
judgments, especially when manipulating the sensory feedback on which
these judgments are made.
The present study investigated how perception
might be influenced by sensory feedback to contribute to height
estimations and obstacle stepping in PD relative to healthy age-matched
control participants. Perceptual judgment accuracy was evaluated by
judging 3 typically encountered obstacle heights in 2 sensory feedback
conditions: (1) vision of foot available and (2) without vision of foot
(reliance on proprioceptive feedback to estimate height). Then
participants proceeded to walk and step over the obstacle. Fifteen
individuals with PD and 15 healthy control participants completed the
task.
As seen with toe elevation, toe elevation variability, and toe
error measures, individuals with PD overestimated the obstacle height
and were significantly more variable when relying solely on
proprioception (in contrast to when vision was available) compared with
healthy controls, although no differences between groups in obstacle
crossing were found.
These results support the notion that sensory
deficits may contribute to inaccuracy of perceptual judgment and has the
potential to contribute to gait behaviors such as tripping and falling,
especially when vision is not available. Future studies should
carefully consider the impact of sensory and perceptual deficits that
might contribute to movement planning problems and consequentially
movement impairments.
