Locomotor behavior of bonnet macaques after spinal cord injury.

Analysis of locomotor behavior after spinal cord injury is widely demonstrated in rodents. In the present investigation, the bonnet monkeys (Macaca radiata) were trained preoperatively to walk in bipedal fashion on the uphill and downhill side of a staircase runway. Surgical hemisection was induced unilaterally in the right side of spinal cord at T12-L1 level in trained macaques. The spinal hemisected animals showed significant impairments in bipedal locomotion with few errors on staircase during the initial part of the postoperative period. In subsequent periods, the walking capability of these operated monkeys gradually improved while traversing the staircase and recovered close to preoperative level by the fourth postoperative month, evaluated using a locomotor behavior grading technique. The results of this study demonstrate the recovery of bipedal locomotion of spinal hemisected macaques on the staircase for a postoperative period of up to 1 year. This study suggests that the mechanisms underlying the recovery of locomotor functions in these monkeys to near normal level may be due to the contribution of spared fibers in lesioned spinal cord and/or probably reflect the mature function of the central pattern generator for locomotion in the spinal cord under the control of remaining descending and afferent units.