Doctor of Philosophy (PhD)
In this dissertation three studies were used to help improve the understanding of eye- hand coordination control of visuomotor reaching tasks with varying cognitive loads. Specifically, we considered potential performance differences based on eye-movements, postural influences, as well as fitness level of the young adult participants. A brief introduction in chapter 1 is followed by a detailed literature review in chapter 2. Results from the three studies presented in chapter’s 3-5 further advance our knowledge of the integrated control used for goal-directed visually-guided reaches. In the first study (chapter 3), the additional cost associated with the use of smooth pursuit slowed hand movement speed when the eyes and hand moved in distinct directions, yet improved accuracy over the use of saccadic eye movements and eye fixation. We concluded that eye-movement choice can influence various types of visually-guided reaching with different cognitive demands and that researchers should provide clear eye-movement instructions for participants and/or monitor the eyes when assessing similar upper limb control to account for possible differences. In the second study (chapter 4), results revealed slower speed and poor accuracy of hand movements along with less body sway for visually-guided reaching when the eyes and hand moved in opposite directions during eye-hand decoupling compared to when the eyes and hand moved in the same direction (eye-hand coupling). In contrast, standing up did not significantly influence reaching performance compared to sitting. We concluded that increases in cognitive demands for eye-hand coordination created a greater need for postural control to help improve the goal- directed control of reaching. In the third study (chapter 5), we found no evidence of eye-hand coordination differences between highly fit or sedentary participants, yet cerebral activation in the centro-parietal location differed between tasks involving eye-hand coupling/decoupling. We concluded that reaching performance declines accompanied increased sensorimotor demands during eye-hand decoupling that may link to prior/current athletic experience and not fitness level. Overall, alterations in visually-guided goal-directed reaching movements involving eye-hand coupling and decoupling depend on changes in eye-movements utilized and not on low threat postural changes or fitness levels of the young adults performing the task.
Yeomans, Matthew Alan, "Eye-Hand Coordination Varies According to Changes in Cognitive-Motor Load and Eye Movements Used" (2020). LSU Doctoral Dissertations. 5313.