Motor reactions to perturbations of gait: proprioceptive and somesthetic involvement.

If an obstacle impedes the forward swing of a cat's foot during stepping, the animal responds by rapidly lifting the foot over the obstacle. Electrical activity of hindlimb muscles was recorded during such reactions in conscious cats. After anaesthesia of the dorsum of the foot, some muscles no longer took part in the reactions and simple stretch responses were observed in the ankle flexors, which had previously shown a more complex pattern of activation. This result emphasizes the importance of cutaneous afferents in contributing to the control of motor responses to unexpected perturbations.