Abstract
ObjectivesIt 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.MethodsH-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.ResultsAt 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.ConclusionBased 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.
Highlights
Simulating a movement without concomitant motor output is a cognitive activity called motor imagery [MI] and can be experienced by most people [1; 2; 3]
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
This has been evidenced by functional magnetic resonance imaging studies that have shown that primary motor areas, parietal cortices, and the cerebellum, which are normally engaged in the actual execution of movements, are activated during MI [3; 8; 9; 10; 11; 12]
Summary
Simulating a movement without concomitant motor output is a cognitive activity called motor imagery [MI] and can be experienced by most people [1; 2; 3]. The involvement of the primary motor cortex during MI has been evidenced by the increased size of motor evoked potentials (MEPs), induced by transcranial magnetic stimulation (TMS), as compared to rest [13]. The magnitude of this MEP change, reflecting an increase of corticospinal excitability, is of various amount from one study to another [14]. It has been recently recommended to assess the full recruitment curve of the MEP rather than recording one stimulation intensity [18]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
