Effects of Activity on Axonal Excitability: Implications for Motor Control Studies

  • David Burke
Part of the Advances in Experimental Medicine and Biology book series (AEMB, volume 508)


In many motor control studies, such as those involving H reflexes in human subjects, stimuli are delivered to nerves in which axons are or have recently been active. It is assumed that a constant stimulus intensity ensures that the same population of axons has been activated, particularly when there is little change in the M wave. However, the neurophysiological literature is replete with evidence that activity depresses axonal excitability. Indeed, some motor control studies have exploited this phenomenon to stimulate specific afferent populations selectively. This chapter will review studies performed in human subjects demonstrating that a voluntary contraction can have profound effects on the excitability of the active axons and on their ability to transmit impulses. These data need to be considered when interpreting human reflex studies.


Conditioning Stimulus Test Stimulus Maximal Voluntary Contraction Chronic Inflammatory Demyelinating Polyneuropathy Motor Axon 
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Copyright information

© Springer Science+Business Media New York 2002

Authors and Affiliations

  • David Burke
    • 1
  1. 1.Department of Neurology, Prince of Wales HospitalSpinal Injuries Research Centre, Prince of Wales Medical Research Institute, University of New South WalesSydneyAustralia

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