Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Psychology

Program Name/Specialization

Cognitive Neuroscience

Faculty/School

Faculty of Science

First Advisor

Dr. Jeffery A. Jones

Advisor Role

Supervisor

Second Advisor

Dr. Quincy J. Almeida

Advisor Role

Supervisor

Abstract

Movement disturbances in individuals with Parkinson’s disease (PD) have been associated with difficulties to plan complex actions. Performance of simple and complex actions overloads resources for individuals with Parkinson’s disease (PD). However, it is unclear if central resources required to plan gait adjustments while walking exacerbate gait disturbances of patients with PD. More specifically, it is unclear how gait impairments, sensory processing, and the dopaminergic system influence the load on processing resources (e.g. cognitive load) during the planning of step modifications. In order to investigate the relative influence of these factors on cognitive load and its impact on gait control, three experiments were conducted that utilized a naturalistic gait task, which challenged planning resources during obstacle avoidance. While the tasks were being performed, dual task interference on gait, and dual task performance were assessed in order to estimate participants’ cognitive load during these tasks. Gait control during obstacle approach and crossing were also evaluated to observe dual task interference on steps known to demand greater planning. In experiment 1 (chapter 2), the influence of gait impairments on planning resources was investigated. The results of this study demonstrated that the planning of gait adaptations in participants with freezing of gait (PD-FOG) resulted in a greater increase in cognitive load, relative to participants with more preserved gait PD-nonFOG (same disease severity without severe gait impairments). The influence of sensory processing on movement planning was investigated in experiment 2 (chapter 3). The results of this study revealed that removal of visual feedback of self-motion affected gait control when the planning of gait adjustments was necessary for successful crossing. In addition, PD patients prioritized walking over the secondary task when visual feedback was reduced, in order to compensate for impaired proprioceptive processing. Lastly, experiment 3 investigated the influence of the dopaminergic system on gait adjustments. The results of this study revealed that dopaminergic replacement partially decreased the effect of cognitive load on gait and drastically improved gait velocity as participants approached obstacles. This study also demonstrates that the cognitive load and the dopaminergic impairments in PD, did not force patients to rely more than healthy participants, on visual information from obstacle as to correct step adjustments. In sum, the current thesis suggests that increases in cognitive load during the planning of gait adaptations causes gait impairments, in individuals with PD. These increases in cognitive load appear to be associated with impaired sensorimotor processing during gait. Dopaminergic activity modulated sensorimotor processing during movement planning and partially the cognitive load caused by movement planning. Finally, the results of these studies suggest that the complexity to plan gait adjustments, while walking, overtax processing resources of individuals with PD causing some observable gait impairments.

Convocation Year

2015

Convocation Season

Spring