Shared and task-specific sensorimotor processing during forward and backward walking in intact adult cats

The neural and biomechanical mechanisms that control a change in direction during locomotion remain poorly understood, particularly sensorimotor processing. In this study, we investigated cycle and phase durations, muscle activity, and cutaneous reflexes during forward (FW) and backward (BW) hindlimb-only walking in seven adult cats stepping on a treadmill at 0.2 m/s, with their forelimbs placed on a stationary platform. We recorded electromyography (EMG) bilaterally from six hindlimb muscles, and cutaneous reflexes were evoked with electrical stimulation of the superficial peroneal (SP) nerve to probe sensorimotor processing. Results show that BW is associated with changes in the timing of EMG activity in all muscles selected and increased EMG amplitudes in specific hindlimb muscles, particularly those that extend the hip Overall, reflex responses evoked by SP nerve stimulation were modulated with phase in both FW and BW. While most response patterns were similar in both directions, some direction-specific patterns emerged, particularly inhibitory responses in ipsilateral and contralateral extensor during BW. Overall, our results are consistent with shared neural circuits for sensorimotor processing when walking forward and backward, with some direction-specific specialized circuits.