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Silent period induced by cutaneous stimulation.
1Department of Neurology, College of Physicians and Surgeons, Columbia University, New York, NY.
Electroencephalography and Clinical Neurophysiology
|October 1, 1991
Summary
Electrical stimulation of skin nerves causes a muscle silent period, more pronounced with painful stimuli. This nociceptive reflex inhibition may involve Renshaw cells, impacting motor neuron activity.
Area of Science:
- Neuroscience
- Motor Control
- Somatosensory System
Background:
- Electrical stimulation of cutaneous nerves during isometric muscle contraction elicits a suppression of electromyographic (EMG) activity, known as the silent period.
- The silent period's characteristics, including its presence across various muscles and nerve stimulation sites, suggest a widespread neural reflex.
- Pain perception correlates with the extent of this inhibitory period, indicating a role for nociceptive pathways.
Purpose of the Study:
- To investigate the characteristics and neural mechanisms of the silent period induced by cutaneous nerve stimulation.
- To determine the timing and extent of motor neuron inhibition during the silent period.
- To explore the potential involvement of Renshaw cells in mediating this nociceptive reflex.
Main Methods:
- Applying electrical stimuli to cutaneous nerves during isometric muscle contraction.
- Measuring EMG activity to identify and quantify the silent period.
- Utilizing transcranial cortical stimulation to assess motor neuron pool inhibition.
- Employing the double stimulus technique to study the recovery cycle of the silent period.
Main Results:
- The silent period is more pronounced with higher stimulus intensities, particularly when perceived as painful.
- This inhibition is observed across diverse limb and cranial muscles, and with stimulation of distant cutaneous nerves.
- Maximal inhibition of the opponens pollicis motor neuron pool occurs 50-70 ms after stimulation, and the silent period is present at short interstimulus intervals (≥100 ms).
Conclusions:
- Nociceptive stimulation induces a widespread motor neuron inhibition, characterized by a silent period.
- The timing and characteristics of the silent period suggest mediation by spinal reflex pathways.
- Results indicate that motor neuron inhibition from nociceptive afferents may be transmitted via Renshaw cells activated by high-threshold cutaneous afferents.