A paradigm of galvanic vestibular stimulation diminishes the soleus muscle H-reflex in healthy volunteers.

Abstract

In this study, we explored how galvanic vestibular stimulation can modify the soleus H-reflex (Hoffman reflex), that is, the excitability of the spinal cord circuits, in healthy humans. Our aim was to demonstrate H-reflex amplitude modulation caused by changing the duration and the intensity of the anodal galvanic vestibular stimulation. Therefore, we measured H-reflex before and after applied vestibular stimulation. This study was conducted in Rehabilitation Clinic, Belgrade, Serbia. The measurements were performed on 5 male volunteers aged 22-30 years. Anodal galvanic stimulation was applied on the right mastoid in prone position. H-reflex was elicited by nervus tibialis stimulation and measured from the right soleus muscle. In three subjects, trains of weak and strong galvanic stimuli (1, 5 and 9) were applied. In two subjects, only a train of 9 strong stimuli was applied. A statistically significant decrease of the H-reflex amplitude after anodal galvanic stimulation was demonstrated in all subjects. The percentage of H-reflex amplitude diminution was between 6 and 18 in subjects with weak and strong stimuli and 5 and 6 in subjects with only 9 strong stimuli. We intend to use this paradigm of stimulation to explore whether the vestibulospinal function exists after spinal cord injury (SCI). If it exists, it can be used to influence the preserved spinal cord circuits after SCI. One of the authors (Nadica Miljković) was partly supported by the Ministry of education, science and technological development, Republic of Serbia, grant OS175016.