The effect of voluntary modulation of the sensory-motor rhythm during different mental tasks on H reflex

• Modulation of the SMR through significantly increases H reflex for all three mental tasks, independent of the direction of modulation.
• Control of SMR amplitude alone was not sufficient to produce a consistent effect on H reflex across different participants.
• Significant negative correlation was found between SMR over the motor cortex and H reflex for relaxed state, NF and MI.

ObjectivesThe aim of this study was to explore the possibility of the short-term modulation of the soleus H reflex through self-induced modulation of the sensory-motor rhythm (SMR) as measured by electroencephalography (EEG) at Cz.MethodsSixteen healthy participants took part in one session of neuromodulation. Motor imagery and mental math were strategies for decreasing SMR, while neurofeedback was used to increase SMR. H reflex of the soleus muscle was elicited by stimulating tibial nerve when SMR reached a pre-defined threshold and was averaged over 5 trials.ResultsNeurofeedback and mental math both resulted in the statistically significant increase of H reflex (p = 1.04·10− 6 and p = 5.47·10− 5 respectively) while motor imagery produced the inconsistent direction of H reflex modulation (p = 0.57). The average relative increase of H reflex amplitude was for neurofeedback 19.0 ± 5.4%, mental math 11.1 ± 3.6% and motor imagery 2.6 ± 1.0%. A significant negative correlation existed between SMR amplitude and H reflex for all tasks at Cz and C4.ConclusionsIt is possible to achieve a short-term modulation of H reflex through short-term modulation of SMR. Various mental tasks dominantly facilitate H reflex irrespective of direction of SMR modulation.SignificanceImproving understanding of the influence of sensory-motor cortex on the monosynaptic reflex through the self-induced modulation of cortical activity.