Ladder Treadmill: A Method to Assess Locomotion in Cats with an Intact or Lesioned Spinal Cord.

After lesions of the CNS, locomotor abilities of animals (mainly cats) are often assessed on a simple flat treadmill (FTM), which imposes little demands on supraspinal structures as is the case when walking on targets. Therefore, the aims of the present work were as follows: (1) to develop a treadmill allowing the assessment of locomotion of intact cats required to place the paws on the rungs of a moving ladder treadmill (LTM); (2) to assess the capability of cats after a unilateral spinal hemisection at T10 to cope with such a demanding locomotor task; and (3) to regularly train cats for 6 weeks on the LTM to determine whether such regular training improves locomotor recovery on the FTM. A significant improvement would indicate that LTM training maximizes the contribution of spinal locomotor circuits as well as remnant supraspinal inputs. Together, we used 9 cats (7 females, 2 males). Six were used to compare the EMG and kinematic locomotor characteristics during walking on the FTM and LTM. We found that the swing phase during LTM walking was slightly enhanced as well as some specific activity of knee flexor muscles. Fore-hindlimb coupling favored a more stable diagonal coupling. These 6 cats were then hemispinalized and trained for 6 weeks on the LTM, whereas the 3 other cats were hemispinalized and trained solely on the FTM to compare the two training regimens. Intensive LTM training after hemisection was found to change features of locomotion, such as the foot trajectory as well as diminished paw drag often observed after hemisection.