Abstract
What sensory information is used to walk toward a goal? Three basic steering strategies have been proposed, based on different sensory variables: (1) Optic flow strategy: null the visual angle between the heading specified by optic flow and the visual direction of the goal (Gibson, 1950; Warren, et al, 2001); (2) Egocentric direction strategy: null the angle between the locomotor axis specified by podokinetic information and the egocentric direction of the goal (Rushton, et al, 1998); (3) Centering strategy: fixate the goal and null the angle between the locomotor axis and the direction of gaze, based on proprioception about eye and head position (Wann & Land, 2001; Hollands et al, 2002). Our aim is to dissociate these strategies during goal-directed walking and investigate how they interact, by manipulating the following variables: (a) central or peripheral goal; (b) visual structure or lights off; (c) yaw head perturbation, active head rotation, or no head rotation. We analyze the time series of head orientation and walking direction to determine the effect of these variables on deviations in the path. If paths deviate with a head perturbation, it indicates a contribution of the centering strategy by involuntary head rotation. If the deviation is reduced by a visible goal, it indicates a contribution of the goal's egocentric direction. If the deviation is reduced in a visually structured environment, it indicates a contribution of optic flow. If the deviation is reduced with active head rotations, it indicates an override of the centering strategy. The results suggest an interaction between these three steering strategies.
Supported by NIH EY10923, CIHR MFE161734