title: An investigation of perceptual-motor processes in people with mild-moderate idiopathic Parkinson’s disease
title: Perceptual-Motor Calibration, Motor imagery, and Body Perception
titleType: Subtitle
Creators: name: Readman, Megan
Publisher: name: Lancaster University
Year: 2022
Subjects: Perceptual Motor Calibration
Parkinson's disease
Body perception
Motor Disorder

description: Safe, successful interaction within one’s environment is contingent upon the perceivers’ ability to rapidly decipher whether the performance of a given action over a visually specified range is permissible. That is, perceivers must be reliably in tune with the maximum extent to which they can perform an action, known as an action boundary. This mapping between the visually specified parameters of the environment and one’s action capabilities is known as perceptual-motor calibration. Indeed, healthy young individuals are reliably calibrated to their action boundaries, and can flexibly adjust their perceptions to accommodate for alterations in their action capabilities. However, this accurate flexible updating occurs in response to somewhat stable variability. Previous studies have typically subjected the perceiver’s morphology to one alteration that then remains stable. For example, hand size has been consistently increased by the addition of a padded prosthesis. However, there are conditions in which motor abilities are subject to continual unstable variability over time, such as in Parkinson’s disease (PD). Many individuals with PD experience unilateral symptom presentation and fluctuations in their motor abilities. Presumably, this leads to variability in perceptual-motor experience relating to ones ability to perform actions. To date, the influence of PD on perceptual-motor calibration remains unknown. Therefore, in the first part of this thesis (Chapters 3-5), I investigated how PD influences ones perceptual-motor calibration capabilities. First, I found that when healthy younger individuals’ grasping ability was artificially varied (in virtual reality), the perceptual system calibrates to the average of all action boundaries experienced (regardless of the frequency of experience with each action boundary). While this study does not directly relate to PD, it serves to inform how we may anticipate PD will influence individuals’ perceptions of their action capabilities. Further experiments showed that individuals with PD perceive their action capabilities for reaching, grasping and aperture passing, comparably to healthy older adult controls. Given the potential functional role of motor imagery when judging one’s action capabilities, I then investigated how specific symptom severity influences individuals with PD’s motor imagery capabilities. Overall symptom severity and tremor did not predict the vividness of motor imagery. However, greater severity of the slowness of movement (bradykinesia) in the left-side of the body was associated with more vivid overall and left-side specific kinesthetic motor imagery. Taken together, these findings imply that perceptual-motor calibration is largely preserved in individuals with mild-moderate idiopathic PD. The second part of this thesis (Chapter 6) then shifted gears and explored the influence of PD on the perceptions of the relative proportions of one’s body. It was found that individuals with PD displayed the same large systematic distortions in the perception of one’s body proportions commonly observed in healthy younger adults. By examining perceptual-motor calibration, and the perception of the relative proportions in individuals with PD, this thesis improve our understanding of the underlying deficits associated with PD. Specifically; I argue that PD is not associated with a deficit in the calibration between perceptual and motor systems.