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

OBJECTIVES: The 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.

METHODS: Sixteen 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.

RESULTS: Neurofeedback 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.

CONCLUSIONS: It 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.

SIGNIFICANCE: Improving understanding of the influence of sensory-motor cortex on the monosynaptic reflex through the self-induced modulation of cortical activity.