Mechanisms of the clasp-knife reflex studied in an animal model

William Z Rymer*, James Charles Houk, P. E. Crago

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

58 Scopus citations


The mechanisms of the clasp-knife reflex were studied in the soleus muscle of an animal model, the decerebrate cat with a dorsal hemisection of the lower thoracic cord. The reflex is shown to be autogenetic, and to depend on muscle length in keeping with previous suggestions. However, the magnitude of the inhibition increases with increasing initial force, and the inhibition is mimicked by gentle manipulation of the muscle and tendon surface. Concurrent muscle afferent recordings showed that the electromyogram (emg) reduction was not a result of a decline in Ia afferent input and was not well related to secondary or tendon organ afferent discharge. It is now known that many group III and some group IV muscle afferents are also activated by muscle stretch and contraction, and we here report limited stretch sensitivity in four non-spindle group II afferents. Since these fiber groups each include afferents that produce inhibition of extensor motoneurons, it is proposed that the clasp-knife reflex may result from the activation of these slowly conducting afferent fibers.

Original languageEnglish (US)
Pages (from-to)93-113
Number of pages21
JournalExperimental Brain Research
Issue number1
StatePublished - Feb 1 1979


  • Clasp-knife reflex
  • Muscle afferents

ASJC Scopus subject areas

  • Neuroscience(all)


Dive into the research topics of 'Mechanisms of the clasp-knife reflex studied in an animal model'. Together they form a unique fingerprint.

Cite this