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Vestibulospinal influences on lower limb motoneurons
Paul M Kennedy1, Andrew G Cresswell, Romeo Chua
1School of Human Kinetics, University of British Columbia, Vancouver, BC V6T 1Z1, Canada. pkennedy@interchange.ubc.ca
Canadian Journal of Physiology and Pharmacology
|November 4, 2004
Summary
Galvanic vestibular stimulation (GVS) modulates lower limb muscles even when not balancing. This research suggests GVS influences motor output via presynaptic inhibitory mechanisms acting on the motoneuron pool.
Area of Science:
- Neuroscience
- Human Physiology
- Motor Control
Background:
- Galvanic vestibular stimulation (GVS) activates the vestibular system using low-intensity electrical currents.
- GVS typically elicits responses in lower limb muscles during active balance control.
- Previous findings suggest GVS may affect muscle activity even outside of standing balance tasks.
Purpose of the Study:
- To review two laboratory studies investigating the effects of GVS on the lower limb motoneuron pool.
- To examine how GVS modulates muscle activity when subjects are not actively maintaining balance.
Main Methods:
- Monopolar monaural galvanic stimulus applied to the vestibular nerve.
- Bipolar binaural GVS applied to the vestibular nerve.
- Electromyographic recordings of lower limb muscles (soleus H-reflex, gastrocnemius motor units).
Main Results:
- Monopolar GVS modified the ipsilateral soleus H-reflex amplitude.
- Bipolar GVS significantly altered the onset of activation and firing frequency of gastrocnemius motor units.
- These effects were observed in muscles not actively engaged in maintaining balance.
Conclusions:
- GVS can modulate lower limb motoneuron pool activity independently of balance tasks.
- GVS likely influences motor output by affecting presynaptic inhibitory mechanisms.
- Further research is warranted to fully elucidate the role of GVS in motor control.