Sep 24, 2004

Contribution of force feedback to ankle extensor activity in decerebrate walking cats

Journal of Neurophysiology
J Maxwell Donelan, Keir Pearson

Abstract

Previous investigations have demonstrated that feedback from ankle extensor group Ib afferents, arising from force-sensitive Golgi tendon organs, contributes to ankle extensor activity during the stance phase of walking in the cat. The objective of this investigation was to gain insight into the magnitude of this contribution by determining the loop gain of the positive force feedback pathway. Loop gain is the relative contribution of force feedback to total muscle activity and force. In decerebrate cats, the isolated medial gastrocnemius muscle (MG) was held at different lengths during sequences of rhythmic contractions associated with walking in the other three legs. We found that MG muscle activity and force increased at longer muscle lengths. A number of observations indicated that this length dependence was not due to feedback from muscle spindles. In particular, activity in group Ia afferents was insensitive to changes in muscle length during the MG bursts, and electrical stimulation of group II afferents had no influence on the magnitude of burst activity in other ankle extensors. We concluded that the homonymous positive force feedback pathway was isolated from other afferent pathways, allowing the use of a simple model...Continue Reading

  • References23
  • Citations46

References

Mentioned in this Paper

Biochemical Pathway
H-Reflex
Meissner's Corpuscle
Ankle
Ankle Joint Structure
Leg Length Inequality
Contraction (Finding)
Soleus Muscle Structure
Motor Neurons
Neuromuscular System

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