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Role of Stereopsis Losses in Older Adults’ Performance

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Role of Stereopsis Losses in Older Adults’ Performance ROLE OF STEREOPSIS LOSSES IN OLDER ADULTS’ PERFORMANCE ON THE FINE-GRAIN MOVEMENT ILLUSION TASK by Marlena Pearson Honours Bachelor of Science, Psychology, Nipissing University, North Bay, Ontario, 2014 Honours Bachelor of Arts, Criminal Justice, Nipissing University, North Bay, Ontario, 2014 A thesis presented to Ryerson University in partial fulfillment of the requirement for the degree of Master of Arts in the program of Psychology Toronto, Ontario, Canada, 2017 © Marlena Pearson, 2017 Author’s Declaration AUTHOR'S DECLARATION FOR ELECTRONIC SUBMISSION OF A THESIS I hereby declare that I am the sole author of this thesis. This is a true copy of the thesis, including any required final revisions, as accepted by my examiners. I authorize Ryerson University to lend this thesis to other institutions or individuals for the purpose of scholarly research I further authorize Ryerson University to reproduce this thesis by photocopying or by other means, in total or in part, at the request of other institutions or individuals for the purpose of scholarly research. I understand that my thesis may be made electronically available to the public. ii Role of Stereopsis Losses in Older Adults’ Performance on the Fine-Grain Movement Illusion Task Master of Arts, 2017 Marlena Pearson Psychology, Ryerson University Abstract Accurate motion perception is necessary for older adults to safely navigate their environments. Yet it is not clear how stereopsis losses contribute to findings of motion perception deficits in older adults. To assess the contribution of stereopsis losses, three groups (younger adults, older adults with intact stereopsis, older adults with poor stereopsis) were recruited for a fine-grain movement task. The distance participants perceived a dot to move across a computer screen was assessed using a staircase procedure. While all participants perceived the dot to move further than the actual distance, older adults with poor stereopsis showed more exaggeration in their estimates than younger adults and older adults with intact stereopsis. However, the groups did not differ in the intraindividual variability of their estimates. These results suggest stereopsis losses in the context of aging may signal neural or oculomotor changes that result in reduced accuracy of positional perception. iii Acknowledgments The completion of my MA thesis was made possible through the extraordinary support provided at Ryerson University. First and foremost, I greatly appreciate the guidance of Dr. Maureen Reed, my thesis advisor. Maureen’s high standards and attention to detail were instrumental in my success. Many thanks to Dr. Todd Girard and Dr. Lixia Yang for agreeing to serve on my thesis defense committee. During the process of refining my thesis, their feedback was invaluable. I would also like to thank Carson Pun for his technical assistance with programming in E-Prime. Finally, I gratefully acknowledge the support of my partner (Alain Carlson), friends, and family. I am excited to begin my PhD work this fall! iv Table of Contents Author’s Declaration ............................................................................................................................. ii Abstract ................................................................................................................................................ iii Acknowledgments ............................................................................................................................... iv List of Tables ....................................................................................................................................... ix List of Figures ....................................................................................................................................... x List of Appendices ............................................................................................................................... xi Introduction ........................................................................................................................................... 1 Visual Declines with Aging .............................................................................................................. 1 Effects of Aging on Structure of the Retina and Visual Cortex ....................................................... 2 Neural Effects of Aging: Neural Noise Hypothesis .......................................................................... 4 Age-Related Neural Changes Affecting Motion Perception ............................................................ 6 Mechanisms by Which Stereopsis Losses May Indicate Losses in Motion Perception ................... 7 Importance of Stereopsis in Aging ................................................................................................. 10 Motion Perception, Stereopsis, and Aging ..................................................................................... 12 Research Questions ......................................................................................................................... 13 Research Question 1: Do older adults show less accuracy in their motion estimates than young adults, and are these differences influenced by older adults’ stereoacuity? ......................... 13 Research Question 2: Do older adults show less precision in their motion estimates than young adults, and are these differences influenced by older adults’ stereoacuity? ......................... 13 v Research Question 3: Is the difference in the magnitude of change in motion estimates between central and peripheral vision different in younger and older adults, and are these differences influenced by older adults’ stereoacuity? ............................................................................. 14 Research Question 4: For older adults, are changes in age and stereoacuity associated with changes in central and peripheral performance? ................................................................... 15 Methods .............................................................................................................................................. 16 Participants ...................................................................................................................................... 16 Measures ......................................................................................................................................... 18 Visual and medical history. ........................................................................................................ 18 Cognitive assessment .................................................................................................................. 19 Stereoacuity. ............................................................................................................................... 19 Visual acuity ............................................................................................................................... 20 Eccentric fixation ........................................................................................................................ 21 FGMI task ................................................................................................................................... 22 Procedure ........................................................................................................................................ 24 Statistical Analyses ......................................................................................................................... 25 Results ................................................................................................................................................. 27 Research Question 1: Do older adults show less accuracy in their motion estimates than young adults, and are these differences influenced by older adults’ stereoacuity? ............................. 27 vi Research Question 2: Do older adults show less precision in the linear extent of their movement estimates than young adults, and are these differences influenced by older adults’ stereoacuity? ............................................................................................................................. 30 Research Question 3: Is the difference in the magnitude of change in motion estimates between central and peripheral vision different in younger and older adults, and are these differences influenced by older adults’ stereoacuity? ................................................................................. 33 Research Question 4: For older adults, are changes in age and stereoacuity associated with changes in central and peripheral performance? ....................................................................... 36 Discussion ........................................................................................................................................... 38 Relationships between Aging Alone and Central and Peripheral Accuracy and Precision of Motion Estimates ................................................................................................................................... 38 Relationships between Stereoacuity Losses in the Context of Aging and Central and Peripheral Accuracy and Precision of Motion Estimates ........................................................................... 44 Limitations .....................................................................................................................................
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