| The goal of this thesis was to examine the roles of vision during planning and execution of adaptive locomotion. Successful locomotion in a dynamic environment demands a continuous update of information about environmental features such as presence of obstacle, terrain layout, and surface characteristics. Specifically during obstacle avoidance, the most important environmental information is obstacle location and obstacle height. The height of the obstacle not only affects the strategy used for obstacle avoidance (step over or go around—Patla, 1997), but also affects the limb adjustments and the whole body stability during the adaptive step (Patla & Riedtjk, 1993). The position of the obstacle affects the step width and step length during the approach phase (Patla, 1991). Additionally, when the task involves stepping over a dynamic obstacle (i.e. change in size, and/or change in position), the information about obstacle movement is very critical for success in the task. In order to understand the effects of dynamic environmental information (changes in obstacle size and location) during avoidance strategies, this thesis examined two main questions: (1) how does the perception of a changing obstacle (size/position) acquired during static visual sampling, under informational conflict, affect feed-forward planning of the adaptive step? (2) How does the perception of a changing (size/position) obstacle acquired during dynamic visual sampling, under informational conflict, affect feed-forward planning and on-line control of the adaptive step? These questions were examined in a series of five experiments. (Abstract shortened by UMI.)... |
