BOUYER, L.J.*; ROSSIGNOL, S.; CRSN, Univ. of Montreal; CRSN, Univ. of Montreal: Adaptive locomotor capacity of chronic spinal cats following changes in sensory feedback.

To further address the question of spinal plasticity, we used 2 complementary denervation protocols. In protocol #1, a motor denervation was performed, cutting the nerve to ankle extensors Lateral Gastrocnemius and Soleus (LGS). Two days after the denervation, cats showed a large yield at the ankle. This yield was gradually compensated in 10 days, by increasing the amplitude of remaining ankle extensor Medial Gastrocnemius (MG). Subsequently cutting Plantaris in one cat led to a second compensation involving a further increase in MG amplitude over a similar 10-day time course. In protocol #2, a gradual cutaneous denervation was performed by sequentially cutting all five cutaneous nerves from the right hindpaw in one cat. Cutting the Deep Peroneal, Caudal cutaneous sural, and Saphenous nerves produced very little changes in the quality of locomotion. Cutting the fourth nerve (Superficial Peroneal), produced a locomotor deficit that consisted of dragging the paw on the dorsum during swing and keeping the paw plantarflexed during stance. After 8 days of training on the treadmill, an almost complete compensation occurred. Paw was only dragged 40% of the swing phase, and stance occurred on the plantar paw surface, with weight bearing. Cutting the last cutaneous nerve (Tibial) brought back the paw placement deficit, and no compensation occurred despite 71 days of training. A similar denervation can easily be compensated by non-spinal cats, however. We conclude that spinal cats, despite the absence of supraspinal control structures, have a large capacity for adaptive compensation after changes in sensory feedback. This capacity is however less extensive than in normal cats, but provides support for using locomotor training to enhance rehabilitation.