Plasticity of the extensor group I pathway controlling the stance to swing transition in the cat

J Neurophysiol. 1995 Dec;74(6):2782-7. doi: 10.1152/jn.1995.74.6.2782.


1. This study examines whether the efficacy of polysynaptic group I excitatory pathways to extensor motoneurons are modified after axotomy of a synergistic nerve. Previously, it has been shown that stimulation of extensor nerves at group I strength can extend the stance phase and delay swing. Stimulation of the lateral gastrocnemius and soleus (LG/S) nerve prolongs stance for the duration of the stimulus train, whereas stimulation of the medial gastrocnemius (MG) nerve moderately increases stance. Our hypothesis was that after axotomy of the LG/S nerve the efficacy of the MG group I input would increase. 2. This idea was tested in 10 adult cats that had their left LG/S nerves axotomized for 3-28 days. On the experimental day the cats were decerebrated and the left (experimental) and right (control) LG/S and MG nerves were stimulated during late stance as the animals were walking on a motorized treadmill. A significant increase in the efficacy of the left MG nerve occurred 5 days after axotomy of the LG/S nerve when compared with the control response. By contrast, the previously cut LG/S nerve showed a reduction in efficacy after 3 days compared with the control limb. 3. Functionally, this plasticity may be an important mechanism by which the strength of the group I pathway is calibrated to different loads on the extensor muscles.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Axons / physiology
  • Cats
  • Electromyography
  • Female
  • Hindlimb / innervation
  • Male
  • Motor Neurons / physiology
  • Muscle Denervation
  • Muscle, Skeletal / innervation
  • Muscle, Skeletal / physiology
  • Neural Pathways / cytology
  • Neural Pathways / physiology*
  • Neuronal Plasticity / physiology*
  • Neurons, Afferent / physiology
  • Posture / physiology*
  • Reflex / physiology