Modulation of the soleus H-reflex following galvanic vestibular stimulation and cutaneous stimulation in prone human subjects.
There is evidence to suggest that vestibular and somatosensory inputs may interact when they are processed by the central nervous system, although the nature of the individual sensory contributions to this interaction is unknown. We examined the effects of a combined vestibular and cutaneous conditioning stimulus on the motoneuron pool that supplies the soleus muscle via the Hoffman reflex (H-reflex). We applied galvanic vestibular stimulation (GVS; bipolar, binaural, 500 ms, 2.5-mA square-wave pulse) and cutaneous stimulation (medial plantar nerve; 11 ms, three-pulse train, 200 HZ) to prone human subjects and examined changes in the amplitude of the H-reflex. GVS alone caused facilitation (approximately 20%) of the H-reflex, whereas ipsilateral cutaneous stimulation alone caused a 26% inhibition. Paired GVS and cutaneous stimulation resulted in a linear summation of the individual conditioning effects. H-reflex amplitudes observed after paired conditioning with GVS and cutaneous stimulation could be predicted from the amplitudes observed with individual conditioning. These results suggest that in the prone position, when the muscles are not posturally engaged, vestibular and somatosensory information appear to sum in a linear fashion to influence the reflex response of lower limb motoneurons. Muscle Nerve 40: 213-220, 2009.
Neurophysiology Laboratory, Department of Human Health and Nutritional Sciences, University of Guelph, Guelph, Ontario N1G 2W1, Canada.
Catherine R
CR
Lowrey
Leah R
LR
Bent
D000328:Adult; D001703:Biophysics; D004558:Electric Stimulation / Q000379:methods; D004576:Electromyography / Q000379:methods; D005260:Female; D007839:Functional Laterality; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D016014:Linear Models; D008297:Male; D009046:Motor Neurons / Q000502:physiology; D018482:Muscle, Skeletal / Q000502:physiology*; D009434:Neural Pathways / Q000502:physiology; D011187:Posture / Q000502:physiology*; D011930:Reaction Time / Q000502:physiology; D012867:Skin / Q000294:innervation*; D014722:Vestibule, Labyrinth / Q000294:innervation*