Fig. 1.

Locomotion tasks. A: the experimental box was divided into 2 corridors. In 1 of the corridors the floor was flat, while the other corridor contained a horizontal ladder. White circles on the crosspieces of the ladders schematically show placements of cat forelimb paws. B and E: average durations of the step cycles in different cats during simple (B) and ladder (E) locomotion. C and F: average step duty factors (ratios of stance duration to cycle duration) in different cats during simple (C) and ladder (F) locomotion. D and G: average durations of the step cycles taken for the analysis of activity of different pyramidal tract neuron (PTN) groups during simple (D) and ladder (G) locomotion. In B–G vertical bars are SDs.