The development and recovery of motor function in spinal cats. I. The infant lesion effect.

Normal development of motor function was compared to that of cats with spinal transections at birth (newborn operates) or at approximately two weeks after birth (two week operates). Newborn operates expressed motor behavior not seen until sometime later in normal newborn cats, suggesting that this behavior is normally suppressed by descending systems in newborn cats. After reaching adulthood, the motor performance of newborn operates surpassed that of both two week operates and chronic adult operates (cats with spinal cord transection in adulthood), suggesting that the earlier transection occurs, the greater the recovery of motor function. Transection at birth may alter the course of spinal cord development, accounting for the differences in motor performance among the three age groups.