Balance in the cat: role of the tail and effects of sacrocaudal transection.

To determine whether the tail of the domestic cat plays a role in balance during locomotion, four cats were trained to traverse a narrow beam. To challenge balancing ability, a sudden lateral displacement was imparted to the beam as the subject was crossing. Freeze-frame videotape analysis revealed that cats responded to beam movement by rapidly moving the tail in the opposite direction. Adjustment of the tail contributed to realignment of the hips over the beam and enabled the animal to remain aboard the beam. Following complete sacrocaudal spinal transection, that eliminated supraspinal control to only the tail, cats fell significantly more often in response to movements of the beam. The importance of the cat's tail for balance, and the utility of this system for modeling functional consequences of spinal cord injury and therapeutic interventions, are discussed.