Master of Science (MSc)
Faculty of Science
The purpose of the current thesis was to investigate the influence of dopamine replacement on performance during bimanual coordination in individuals with Parkinson’s disease (PD) There has been conflicting research on the cause of movement impairments such as coordination deficits, slowed switching and upper limb freezing that occur during coordinated movements It is unclear whether decreased function of the dopaminergic system after withdrawal from dopamine replacement is responsible for these deficits Healthy age-matched control participants were compared to PD participants in two experiments to determine the movement impairments that occurred during three-dimensional wrist flexion-extension bimanual coordination as a result of PD. In addition, individuals with PD were compared without (‘off’) and with (‘on’) dopamine replacement in both experiments to determine whether modulation of the dopaminergic system influenced coordinated movements.
In Experiment 1, continuous bimanual coordination was performed in m-phase (simultaneous wrist flexion and extension) and anti-phase (flexion of one wrist while extending other wrist) with movements externally paced with increasing across seven cycle frequencies (0.75 to 2 Hz). Visual feedback was also manipulated in one of three sensory conditions no vision, normal vision or augmented vision. Visual feedback, phase and cycle frequency manipulation was performed to determine whether other deficits (e.g. sensory and/or attentional deficits) may influence coordinated movements Despite reduced amplitude of movements in both limbs of individuals with PD (PD ‘off’), coordination deficits were not observed in PD compared to healthy control participants. In addition, there was an increased occurrence of upper limb freezing (ULF) when cycle frequency demand was greater Dopamine replacement did increase the amplitude of movements in individuals with PD but did not influence coordination performance or the occurrence of ULF.
In Experiment 2, coordinated movements were initiated in either m-phase or antiphase and participants were required to voluntarily switch to the other phase pattern when an auditory cue was presented Trials were performed at one of two cycle frequencies (1 or 2 Hz) and one of two sensory conditions (no vision or normal vision) to determine whether other deficits (e.g. sensory and/or attentional deficits) may influence coordinated movement. In addition, a separate block of trials were performed in anti-phase coordination with an auditory cue that did not require a switch Non-switching trials were included to investigate whether the presence of a distracting cue could evoke ULF comparable to when switching between movements was required PD ‘off’ participants demonstrated slower switching, more delayed responses and deficits in coordination performance when compared to healthy control participants. The increased demand of cycle frequency particularly when initiating anti-phase coordination, after voluntary switching and with the presence of the auditory cue without switching contributed to a large occurrence of ULF in individuals with PD. Dopamine replacement improved the ability to switch between phase patterns but had no overall influence on coordination performance or the occurrence of ULF.
Overall, the results of the current thesis demonstrated that dopamine replacement can improve motor symptoms during coordinated movements (e g hypometna and bradykinesia) but does not contribute to coordination performance or ULF in individuals with PD. As a consequence, it was concluded that coordination deficits and ULF are not caused by the dysfunctional dopaminergic system but rather associated to secondary impairment caused by PD. The movement impairments caused by secondary dysfunction of PD were proposed to be associated with increased attentional demands and possible executive dysfunction related to fronto-stnatal pathways that cannot be modulated by dopamine replacement. Thus, treatment of complex movement impairments such as coordination deficits and ULF may benefit from rehabilitation or non-dopamine therapies that focus on the global dysfunction caused by PD.
Brown, Matt, "The Influence of Dopamine Replacement on Movement Impairments During Bimanual Coordination in Parkinson’s Disease (PD)" (2010). Theses and Dissertations (Comprehensive). 1016.