Figure 1.

Locomotion tasks. A: A box with corridors 2.5 m long and 0.3 m wide served as an experimental chamber. Four locomotor tasks with different demands on visual guidance of stepping were studied: (1) walking on a flat surface in the dark: simple surface and no visual input; (2) walking on a flat surface in the light: simple surface and visual information is available but is not required for locomotion; (3) walking on crosspieces of a horizontal ladder: highly structured surface, but regular and familiar; and (4) walking through a pathway with many small stones (gray shapes, n=51): highly structured surface, which is irregular and new every day. Colored circles on the crosspieces of the ladders and between stones schematically show placements of cat right (pink) and left (orange) forelimb paws, not to scale. B: Photograph of cat 3 walking in the chamber on the flat surface in the light. C: Photograph of the same cat walking on crosspieces of horizontal ladder. B, C: Photographs were taken after end of experiments and removal of implants. D: Walking velocity of different cats during the four locomotor tasks. E: Stride length of cats during the four locomotor tasks. D, E: Error bars are SDs.