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Conditioning of H reflex by a preceding subthreshold tendon reflex stimulus
Journal of Neurology, Neurosurgery, and Psychiatry
|June 1, 1977
Summary
Mechanical tendon taps modulate soleus H reflex excitability. A brief facilitation is followed by prolonged inhibition, suggesting Ia nerve fiber activation and potential transmitter depletion in spinal cord injury patients.
Area of Science:
- Neuroscience
- Motor Control
- Human Physiology
Background:
- The soleus H reflex is a measure of spinal cord excitability.
- Understanding reflex modulation is crucial for motor control research.
Purpose of the Study:
- To investigate the effects of mechanical tendon taps on soleus H reflex excitability.
- To determine if these effects are mediated by Ia afferent pathways.
Main Methods:
- Mechanical subthreshold tendon taps applied to Achilles, biceps, or quadriceps tendons.
- Recording of soleus H reflex responses.
- Assessment of effects during leg ischemia.
Main Results:
- Tendon taps consistently produced early facilitation followed by long-lasting inhibition of the soleus H reflex.
- Similar effects observed in individuals with complete spinal cord transection.
- Modulations ceased after inducing leg ischemia.
Conclusions:
- Soleus H reflex modulation by tendon taps involves activation of Ia afferent nerve fibers.
- Long-lasting inhibition may result from neurotransmitter depletion.
- These mechanisms are preserved even after complete spinal cord injury.