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Human masseter inhibitory reflexes evoked by repetitive electrical stimulation
P O Hansen1, P Svensson, L Arendt-Nielsen
1Danish Pain Research Center and Department of Neurology, Aarhus University Hospital, Aarhus, Denmark. orm@dadlnet.dk
Summary
The masseter inhibitory reflex (MIR) magnitude reduction after repetitive stimulation is not solely linked to nociceptive processing. This suggests habituation or disinhibition may explain the observed changes in trigeminal sensory intensity.
Area of Science:
- Neuroscience
- Physiology
- Pain Research
Background:
- The masseter inhibitory reflex (MIR) is a trigeminal reflex.
- Understanding MIR's relation to nociception is crucial for pain processing insights.
- Repetitive stimulation can alter sensory perception.
Purpose of the Study:
- To investigate the relationship between the masseter inhibitory reflex (MIR) and nociceptive processing in the trigeminal system.
- To determine if changes in MIR correlate with perceived sensory intensity after repetitive stimulation.
Main Methods:
- Quantified MIR and compared with psychophysical measures in 10 healthy subjects.
- Used repetitive peri-oral electrical stimulation.
- Analyzed early (ES1) and late (ES2) periods of exteroceptive suppression, and excitation periods (ISP, PSP) using a computer algorithm.
Main Results:
- A consistent reduction in the magnitude of the late period of exteroceptive suppression (ES2) was observed.
- This reduction occurred regardless of whether stimulation was below or above the pain detection threshold.
Conclusions:
- The reduction in ES2 magnitude is not exclusively related to nociceptive processing.
- Habituation or disinhibition of inhibitory pre-motor neurons are potential mechanisms for the observed ES2 changes.