The relationship between the soleus H-reflex amplitude and vibratory inhibition in controls and spastic subjects: II. Computer model

A.A.J. Hilgevoord*, L.J. Bour, J.H.T.M. Koelman, B.W. Ongerboer de Visser

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

2 Citations (Scopus)

Abstract

A computer model is presented that describes soleus H-reflex recruitment as a function of electric stimulus intensity. The model consists of two coupled non-linear transfer functions. The first transfer function describes the activation of muscle spindle (Ia) afferent terminals as a function of the electric stimulus intensity; whereas the second describes the activation of a number of motoneurons as a function of the number of active Ia afferent terminals. The effect of change in these transfer functions on the H-reflex recruitment curve is simulated. In spastic patients, a higher average maximal II-response amplitude is observed in combination with a decreased H-reflex threshold. Vibration of the Achilles tendon reduces the H-reflex amplitude, presumably by reducing the excitatory afferent input. Vibratory inhibition is diminished in spasticity. In the model, the afferent-motoneuron transfer function was modified to represent the possible alterations occurring in spasticity. The simulations show that vibratory suppression of the H-reflex is determined only in part by the inhibition level of the afferent input. With a constant level of presynaptic inhibition, the suppression of reflexes of different sizes may vary. A lowering of the motoneuron activation thresholds in spastic patients will directly contribute to a decrease of vibratory inhibition in spasticity.

Original languageEnglish
Pages (from-to)259-266
Number of pages8
JournalJournal of electromyography and kinesiology
Volume6
Issue number4
DOIs
Publication statusPublished - 1 Dec 1996
Externally publishedYes

Keywords

  • Models
  • Soleus H-reflex recruitment
  • Spasticity
  • Vibratory inhibition

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