Direction of galvanically-induced vestibulo-postural responses during active and passive neck torsion.
The direction of a postural response induced by galvanic vestibular stimulation depends on the head and trunk position. The relative importance of afferent information (proprioception) and efferent motor command/corollary discharge is unknown. We studied the direction of body sway evoked by galvanic vestibular stimulation in 9 healthy subjects during active and passive head positioning at 0 degrees frontal position, 35 degrees to the left, and 75 degrees to the right, using a custom-built collar. At 0 degrees and 75 degrees there were no significant differences in sway direction between active and passive head positioning. The galvanic stimulation invoked sway toward the anode, mainly in the inter-aural direction. The sway direction differed significantly between active and passive positioning at 35 degrees to the side (p < 0.05). When the head was actively kept in this position, the body sway was mainly in an inter-aural direction. The sway shifted to a naso-occipital direction when the head was passively positioned at 35 degrees. Our results indicate that the afferent proprioceptive information has the largest influence on the direction of the galvanically-induced postural response, although some dependence on efferent motor commands and non-linear cervical proprioception cannot be ruled out entirely.
Fransson
P A
PA
Department of Otorhinolaryngology, University Hospital, Lund, Sweden.
Karlberg
M
M
Sterner
T
T
Magnusson
M
M
D000328:Adult; D004558:Electric Stimulation; D005260:Female; D019416:Head Movements / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011187:Posture / Q000502:physiology*; D011434:Proprioception; D014722:Vestibule, Labyrinth / Q000502:physiology*