The Effects of Aging on Motion Perception in Healthy Older Adults

Abstract

<p>Motion perception is required for nearly all aspects of daily living. Previous work has shown that the ability to perceive a variety of different types of motion is significantly affected by increasing age. The research described in this thesis further probes the complex effects of aging on motion perception using a number of different stimulus configurations and performance measures. In order to relate psychophysical performance to neurophysiological recordings, we used two different notched-noise masking techniques to estimate the directional selectivity of masking in younger and older adults. We found evidence to suggest that the directionally-selective mechanisms of older adults are more broadly tuned than their younger counterparts, which is consistent with the animal literature that links decreased neural inhibition with broader directional tuning. Behaviourally however, task-specific contrast sensitivity may play a role in explaining that result. We also uncovered a previously unobserved difference between horizontal and vertical motion perception which bears further study. We also tested peripheral motion perception both under focused and divided attentional conditions. Older adults were impaired compared to younger adults when asked to make judgments about motion patterns in the peripheral vision field, but they were not differentially impaired under divided attention conditions. The findings presented in this thesis paint a more complex picture of how increasing age impairs motion perception than previously described. Specifically, our observations show that age effects interact with stimulus contrast, attention, and motion direction, and these interactions each present an interesting avenue for further exploration.</p>