Title: “Global and time-dependent postural responses to saccadic eye movements”
Supervisor: Dr. Mark G. Carpenter
Committee members: Dr. Romeo Chua, Dr. J. Timothy Inglis
Abstract: Vision is a sensation that allows for interaction with the visual environment and supplies important information to the central nervous system to facilitate postural control. In addition to retinal information taken in during fixation, extraretinal information supplied by movements of the eyes is thought to contribute to the visual control of posture. Neuroanatomical connections between regions of oculomotor and postural control may support this relationship and contribute to proposed mechanisms of interaction. Attempts to characterize this relationship have reported an effect of saccade tasks on postural control; however, results and methodology vary widely across the literature. Additionally, some evidence has suggested that time-dependent changes in postural control may be evident on a shortened time scale.
The first purpose of this thesis is to re-examine the global relationship between saccadic eye movements and postural control. This will be done by examining the net effect of performing various types of saccades over the length of a quiet standing trial. Specifically, eye movements will be cued by external visual stimuli presented under different conditions of direction and latency. Compared to static fixation, we hypothesize reductions in the amplitude and increases in the frequency of postural responses during saccadic tasks. We also hypothesize differences in the characteristics of postural responses between endogenously and exogenously driven saccades.
The second purpose of this thesis is to determine if there are any time-dependent changes in postural responses relative to the onset of eye movement. This portion of the project will expand on current literature with a novel and exploratory approach to the relationship between saccades and postural control. This will be done by examining the response of each outcome variable time-locked to the onset of each individual saccade and averaged over all saccades by direction. We hypothesize a small but clear average response in the center of pressure position and electrodermal activity with saccades.
This project will characterize posture in terms of both immediate effects and patterns over longer periods of time with various types of eye movements. This research will contribute to a deeper understanding of interactions between the oculomotor and postural control systems, and the different mechanisms that may contribute to the relationship.