Assessing the Contributions of Optic Flow: Strategies to Improve Gait in Parkinson’s Disease

Abstract

Visual cues are suggested to be an effective strategy to improve common gait deficits in individuals with Parkinson’s disease (PD), yet we do not fully understand how vision and other forms of sensory feedback aid gait in disordered populations. The present study evaluates whether optic flow is sufficient to improve gait. Two groups were tested in this study: 20 individuals with idiopathic PD “Off” anti-Parkinsonian medications (average=14.7hrs), and 11 healthy age-matched control participants. Participants walked across a computerized carpet in four visual conditions, the first three conditions were at a self-selected pace: i) Normal Vision: walking across the carpet at a self-selected pace with normal vision available, ii) Ground lines: walking while stepping toward lines, iii) Optic flow cues: walking at a self-selected pace while wearing a visual feedback device (the device provides an illusion of moving lines for feet to step towards), and iv) Optic flow plus: attending to an auditory metronome that matched the self-selected pace of the participant (as determined in condition i). Optic flow did not elicit improvements in step length or velocity for the PD participants; only the ground lines improved step length, which concurs with previous studies. Therefore, optic flow alone could not improve normal step lengths in individuals with PD. Only when vision was available did normal stepping occur. Vision is known to compensate for impairments in proprioception. Our results suggest that conscious perception of motion, produced in part by vision and proprioception, is required for improvements in locomotion. Thus we have provided a glimpse as to why optic flow is not effective.