Optimal stimulation parameters for spinal and corticospinal excitabilities during contraction, motor imagery and rest: A pilot study

Objectives It is commonly accepted that motor imagery (MI), i.e. the mental simulation of a movement, leads to an increased size of cortical motor evoked potentials (MEPs), although the magnitude of this effect differs between studies. Its impact on the spinal level is even more variable in the lite...

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Bibliographic Details
Published in:PloS one 2020-06, Vol.15 (6), p.e0235074-e0235074
Main Authors: Bouguetoch, Amandine, Grospretre, Sidney, Martin, Alain
Format: Article
Language:English
Subjects:
Analysis
Biology and Life Sciences
Contraction
Electromyography
Evoked potentials
Excitability
Imagery
Life Sciences
Medicine and Health Sciences
Mental task performance
Methods
Motor cortex
Motor evoked potentials
Muscles
Neural stimulation
Neurobiology
Neurological research
Neurons and Cognition
Parameters
Physiological aspects
Pyramidal tracts
Recruitment
Reflexes
Research and Analysis Methods
Soleus muscle
Stimulation
Studies
Transcranial magnetic stimulation
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Summary:Objectives It is commonly accepted that motor imagery (MI), i.e. the mental simulation of a movement, leads to an increased size of cortical motor evoked potentials (MEPs), although the magnitude of this effect differs between studies. Its impact on the spinal level is even more variable in the literature. Such discrepancies may be explained by many different experimental approaches. Therefore, the question of the optimal stimulation parameters to assess both spinal and corticospinal excitabilities remains open. Methods H-reflexes and MEPs of the triceps surae were evoked in 11 healthy subjects during MI, weak voluntary contraction (CON) and rest (REST). In each condition, the full recruitment curve from the response threshold to maximal potential was investigated. Results At stimulation intensities close to the maximal response, MEP amplitude was increased by CON compared to REST on the triceps surae. No effect of the different conditions was found on the H-reflex recruitment curve, except a small variation beyond maximal H-reflex in the soleus muscle. Conclusion Based on our results, we recommend to assess corticospinal excitability between 70% and 100% of maximal MEP intensity instead of the classical use of a percentage of the motor threshold and to elicit H-reflexes on the ascending part of the recruitment curve.
ISSN:1932-6203
1932-6203
DOI:10.1371/journal.pone.0235074