Effect of optical flow versus attentional strategy on gait in Parkinson's Disease: a study with a portable optical stimulating device

Background: Several studies have demonstrated the capability of PD subjects to improve gait if appropriate visual cues are provided. Possible explanations referred to attentional factors and to the presence of optic flow on peripheral vision. The aim of the present study was to evaluate separately these two mechanisms in a group of fifteen subjects with Parkinson's Disease at different stages and in a group of ten age-matched controls. Methods: A microprocessor- controlled portable device implementing two different optical stimulation modalities has been used: bilateral continuous optic flow and unilateral reciprocal optical stimulus that is synchronized to the swing phase of gait. The latter allowed for the implementation of an attentional strategy. Results: Results showed that mild PD subjects (H&Y <=2) are responsive to forward oriented optic flow which produces an increment of gait cadence (+ 7.8%) and velocity (+ 8.1%) ( p < 0.05), while PD subjects at more advanced stages (H&Y > 2) tend to be more responsive to the attentional strategy, through an increase of stride length (+ 19.8%) and a compensatory decrease of cadence (- 16.2%). Conclusion: Although stated with caution due to the limited number of considered subjects, a possible descriptive model explaining the above findings is proposed, which correlates the different responsiveness to visual stimulation strategies with the progression of pathology and the consequent changes on the activation levels of the involved motor and associative areas.