The present study evaluated how gait in patients with Parkinson's disease (PD) is influenced by the manipulation of different characteristics of step cues. Two groups - 22 participants with PD "on" dopaminergic medication, and 11 healthy age-matched controls - walked on a computerized carpet under four conditions: (i) self-paced walk (Baseline); (ii) lines on the ground (normal optic flow) (Ground Line); (iii) laser lines (reverse optic flow) (Laser); and (iv) laser lines in a dark environment (Laser Dark). Interestingly, the step length improved in patients with PD regardless of optic flow direction, suggesting that individuals with PD focus attention on the planning of each step discretely. However, when vision of the lower limbs was removed (i.e. the Laser Dark condition), the step length improvement disappeared. Thus, visual cues are only beneficial when the lower limbs can also be seen, suggesting that these cues focus attention on the lower limbs to compensate for a proprioceptive processing deficit. Future research should strive to understand the link between proprioception and attentional focus.
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