Vision and gait in Parkinson's disease: impact of cognition and response to visual cues

Ph.D. ThesisGait impairment is a core feature of Parkinson’s disease (PD) which is difficult to treat due to its multi-factorial nature. Gait dysfunction in PD has been linked to cognitive and visual deficits through separate strands of research. However cognitive and visual functions likely interact (termed visuo-cognition) and have a combined impact on gait. Attempting to further understand the roles of cognition and vision in gait in PD was the motivation behind this thesis. The primary aim was therefore to investigate visuo-cognition and its role in gait in PD. Saccade frequency during gait represents the amount of visual sampling employed when walking and is a useful online behavioural measure of visuo-cognition. However, previous investigations have been limited by lack of robust methodologies, technology and outcome measures. A key objective was therefore to establish robust saccadic measurement with mobile eye-tracking technology in PD and older adult controls. My original contributions to knowledge were that a mobile eye-tracker can measure saccadic activity during gait in PD and controls, but with variable accuracy and reliability for certain characteristics. Cognitive and visual functions were significantly related in both PD and controls, with stronger association in PD. Saccade frequency during gait was significantly reduced in people with PD compared to controls, particularly under dual task. Impaired saccade frequency can be ameliorated with a visual cue; as such intervention significantly increased saccade frequency in PD and controls which was maintained under dual task. Saccade frequency during gait was independently associated with cognitive and visual functions in PD. A structured model demonstrated that visuo-cognitive dysfunction had an indirect effect on gait in PD, with a central role for attention in all relationships involved. The major conclusion from this thesis was that gait impairment in PD is influenced by visuo-cognitive dysfunction, with implication for poor mobility and falls risk.National Institute for Health Research (NIHR) Biomedical Research Unit (BRU). Newcastle University