STANCE CONTROL IN THE CHRONIC SPINAL CAT

1. A longitudinal study of the control of quiet and perturbed stance w as conducted before and for 1 yr after complete spinal transection (T- 12) in a cat trained to stand on a moveable force platform. 2. With da ily training, the spinal cat recovered full weight support and some in termittent control of lateral stability within 1 mo. Within the second month postspinalization, the spinal cat achieved the ability to maint ain independent, unassisted stance (no external support or stimulation ) for up to 45 s during quiet stance, as well as for 62-97% of the tri als of horizontal translations of the support surface. 3. Control of l ateral stability in the spinal cat was severely compromised, however, as eventually the spinal cat always lost its balance. Head movements a nd the tendency for the hindlimbs to initiate stepping movements were more destabilizing than platform translations. 4. Our preliminary resu lts indicate that the recovery of partial lateral stability of the hin dquarters in the spinal cat is the product of passive muscle propertie s and segmental reflexes, which, in isolation, can provide only limite d balance control in the chronic spinal cat.