Dealing with uncertain visual feedback while walking

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Vision contributes essentially to walking by allowing us to detect and define properties of the environment, receive and process self- and object-motion cues, and determine the position of the limbs and body relative to our surroundings. These visual processes, which depend on both an intact visual system and appropriate gaze behaviour, facilitate the identification of hazards, negotiation of obstacles, and control of foot placement. The nervous system must integrate the input it receives from vision with other sensory sources to determine the state of the body/limbs to control and adapt walking in different situations. However, it is faced with a fundamental problem: how to deal with uncertainty. This uncertainty is created, in part, by the limitations of sensory receptors, such as the eye, and body changes from age or disease. In addition, our environment continually changes as we interact and move within it. This leads to environmental uncertainty, which may stem from unpredictable terrain or trajectories of pedestrians and other moving objects, or be caused by changes in ambient lighting. The long-term goal of this program of research is to determine how the nervous system resolves visual and environmental uncertainty to control and to adapt walking. **The proposed research will focus on three complementary objectives: (1) Determine how the brain adapts to altered visual input in the face of uncertainty; (2) Determine the effects of uncertainty on the allocation of gaze and the spatiotemporal relationship between where a person looks and foot placement during visually guided walking; and (3) Identify how the nervous system re-weights vestibular input with increased visual feedback uncertainty while walking in complex environments. In the experiments of these objectives, individuals will be required to walk in situations that require precise foot placement and/or across uneven/irregular terrain. We will quantify foot placement accuracy, balance, and where people fixate as individuals adapt to the constraints of the environment and visual uncertainty created by special glasses, unpredictable motion of objects, or changes in lighting.**The proposed program of research will provide fundamental insight into how the nervous system deals with uncertainty while walking. A detailed understanding of how the brain adapts to altered visual input (Objective 1) is essential given that analogous changes in the quality of vision occur in several situations, including with age, new prescription lenses, and eye disease. Objective 2 will facilitate our understanding about how gaze is allocated in natural environments, how gaze patterns are learned, and how this visual sampling of the world is coupled to foot placement while walking. Because efficient gaze behaviour is essential for using human-machine interfaces (e.g., interactive displays, military simulators), identification of the factors that guide gaze and how gaze patterns are learned can assist in their design and training in their use. Research of Objective 3 will advance our knowledge of the complex interaction between sensory systems for the control of movement. Together, this knowledge will ultimately lead to innovative strategies to improve the mobility of those with neurological and/or eye disease, and facilitate the design of brain/human-machine interfaces used for clinical, military, and entertainment purposes.