Disruption of cutaneous feedback alters magnitude but not direction of muscle responses to postural perturbations in the decerebrate cat

Quadrupeds and bipeds respond to horizontal perturbations of the support surface with muscular responses that are broadly tuned and directionally sensitive. Since the discovery of this directional sensitivity, interest has turned toward the critical sensory systems necessary to generate these responses. We hypothesize that cutaneous feedback aVects the magnitude of muscle responses to postural perturbation but has little eVect on the directionality of the muscle response. We developed a modiWed premammillary decerebrate cat preparation to evaluate the sensory mechanisms driving this directionally sensitive muscle activation in response to support surface perturbation. This preparation allows us the Xexibility to isolate the proprioceptive (cutaneous and muscle receptors) system from other sensory inXuences. We found that loss of cutaneous feedback leads to a signiWcant loss in background activity causing a smaller muscular response to horizontal perturbations. However, the directional properties of the muscular responses remained intact.