The complex role of spindle afferent input, as evidenced by the study of posture control in normal subjects and patients

M. Schieppati, A. Nardone, S. Corna, M. Bove

Research output: Contribution to journalArticlepeer-review

Abstract

This report reviews recent findings from our laboratory on the connectivity of the group II spindle afferent input and the role played by these afferents in the control of quiet and perturbed human stance. At variance with group Ia fibres, which subserve the monosynaptic stretch reflex, the group II fibres, after having entered the spinal cord, make synaptic contacts with a short chain of interneurons which impinge on homonymous motoneurons. Analysis of the short-and medium-latency responses evoked in foot and leg muscles by perturbations of upright stance under different experimental conditions has revealed a role of group II fibres in the production of the medium-latency response. The conduction velocity of group II spindle afferent fibres and their central delay have also been estimated. Furthermore, data from normal subjects and from neuropathic and hemiparetic patients are in favour of a prevailing role of the input from group II fibres in the afferent control of quiet and perturbed stance. Since Ia fibres innervate receptors more sensitive to the velocity of muscle stretch, and II fibres innervate receptors more sensitive to the absolute value of muscle length, it is hypothesised that the major role of the latter in the reflex control of stance reflects the slow velocity and amplitude of sway during quiet upright posture. Indirect evidence supports the conclusion that, also in humans, monoaminergic descending pathways from brainstem nuclei modulate the excitability of the circuits mediating the group II input.

Original languageEnglish
JournalNeurological Sciences
Volume22
Issue numberSUPPL. 1
Publication statusPublished - 2001

Keywords

  • Monoaminergic modulation
  • Posture control
  • Spindle afferent

ASJC Scopus subject areas

  • Dermatology
  • Clinical Neurology
  • Psychiatry and Mental health
  • Neuroscience(all)

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