Master of Kinesiology (MKin)
Faculty of Science
Background: Individuals acquire information about self-motion from the environment which specifies actions necessary to be successful (Fajen & Matthis, 2011). However, concussed individuals demonstrate residual disturbance in execution of postural movement at 30 days post injury, depicting an impaired ability to perceive self-motion in a visually conflicting environment (Slobounov et al. 2006). The objective of this thesis was to investigate the extent to which one’s behaviours on a central field of view task are influenced by the amount and type of peripheral visual movement during a collision avoidance task, as well as to determine the additive effects of changes to balance control through the examination of the behaviours of a previously concussed population. The study utilized the closing doors of a virtual subway train to create an aperture for passage. For the purposes of this study, peripheral visual stimuli was a technique in which objects located within an individual’s peripheral field of view were manipulated to be absent, stationary/relatively stationary (veridical optic flow), or move independent of the participant’s movements (non-veridical optic flow). It was hypothesized that individuals would perform best when the environment provided visual information regarding one’s own self motion. It was expected that a critical point (i.e., when the limits of action are reached and a transition phase into a different action occurs (Warren & Whang, 1987)) would emerge, which would be impacted by the different levels of peripheral visual environment, eliciting a change in critical point. Furthermore, it was anticipated that previously concussed asymptomatic individuals would elicit more variable behaviours (i.e., inconsistent path selection when aperture width remains constant) compared to non-concussed counterparts (Baker & Cinelli, 2014), as a product of the peripheral visual environment.
Methods: Previously concussed (3-12 months prior) asymptomatic young adults (N=12) were recruited, along with age and gender matched non-concussed controls (N=12). Participants walked along a 7m virtual path (via HTC Vive) towards a set of subway doors and were instructed to safely board the train without colliding with the doors. When the participants were 2m from the doors, they began to close at a constant rate such that the final door aperture width at the time of crossing ranged from 35-85cm (in 10cm increments). Participants performed aperture crossing trials during one of four peripheral environments: 1) ground plane only; 2) ground plane plus stationary poles in the peripheral environment; 3) ground plane with stationary humanoids in the peripheral environment; or 4) randomly moving humanoids. Participants were exposed to three trials of each aperture width within each environment for a total of 72 walking trials (6 widths x 4 conditions x 3 trials). Kinematic data was collected using a 3D motion capture system (Optotrak, NDI).
Results: The results revealed that participants executed significant shoulder rotations regardless of aperture width at time of crossing. It was found that non-concussed control subjects executed slightly larger shoulder rotations for smaller apertures (i.e., 35, 45, and 55cm) compared to the largest aperture (p.05), coefficient of variation of velocity (p>.05), or medial-lateral stability during the approach phase (p>.05).
Conclusion: The findings of this study suggest that although a significant difference was found between aperture sizes for non-concussed controls, all individuals were found to employ a more conservative approach (i.e., “one solution fits all” strategy) to ensure success within each of the peripheral visual environments. As such, further research is required to assess the contributions of peripheral body information during an aperture crossing task and further the understanding of the behaviours demonstrated by each group. In addition, a more comprehensive sample of previously concussed asymptomatic individuals from various time points since concussion recovery will provide further insight into potential visuomotor deficits within this population.
Prangley, Alyssa, "Peripheral Visual Motion Sensitivity in Previously Concussed, Asymptomatic Individuals" (2017). Theses and Dissertations (Comprehensive). 1998.