Journal of Neurophysiology, Vol 76, Issue 1 471-491, Copyright © 1996 by APS
A comparison of treadmill locomotion in adult cats before and after spinal transection
M. Belanger, T. Drew, J. Provencher and S. Rossignol
Departement de Physiologie, Faculte de Medecine, Universite de Montreal, Quebec, Canada.
1. The aim of this study was to document the kinematics and the
electromyographic activity recorded from several muscles during treadmill
locomotion in the same cat (N = 4), before and after spinalization by using
a chronic implantation method. Because identical experimental and control
conditions were used, it was possible to establish similarities and
differences in the timing and amplitude of the muscular activity and
kinematics under the intact and spinal conditions in the same animal. The
data presented in this paper were collected when the cats had fully
recuperated a stable locomotor pattern, walking at a constant speed of
approximately 0.4 m/s. 2. The adult spinal cats retained many of the
general locomotor features and electromyographic (EMG) characteristics seen
before transection. However, there were also important differences. 3.
There was a reduction in the step length that was principally due to the
forward placement of the paw at the onset of the stance. Similarly, there
was a decrease in the step cycle duration which was attributed to a
reduction of both the stance and swing phases. 4. The overall angular
excursions of the hip, knee, and ankle were generally similar, although
joints were sometimes more flexed at all phases of the step cycle. In
contrast, the overall excursions of the metatarsophalangeal joints was much
greater in all four cats after spinalization due to a paw drag during the
initial portion of the swing phase that exaggerated the plantarflexion. 5.
There was an increase in the EMG amplitude of the flexor muscles at two of
three joints (i.e., hip, knee, and ankle) in each cat after spinalization.
The change in the EMG amplitude of the extensors did not appear to be as
consistent as that observed in the flexor muscles. When looking at each cat
individually, the postspinalization extensor activity decreased at two of
three joints in two cats, whereas the opposite was true for the other two
cats. 6. There was a delay in the onset of the knee flexor (semitendinosus)
activity while the ankle dorsiflexor (tibialis anterior) activity started
earlier with respect to the beginning of the swing phase. The onset of hip
flexors was somewhat more variable. This change in the timing of flexor
activity was most probably responsible for the paw drag at the onset of the
swing phase. 7. The present results reveal that despite the few
differences, the spinal cord and the hindlimbs afferents are capable of
generating very good locomotor patterns with almost normal kinematics and
EMG characteristics.
