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This Article Full Text Full Text (PDF) All Versions of this Article: 551/3/1033    most recent jphysiol.2003.045971v1 Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Wardman, D. L. Articles by Fitzpatrick, R. C. Search for Related Content PubMed PubMed Citation Articles by Wardman, D. L. Articles by Fitzpatrick, R. C.

Effects of galvanic vestibular stimulation on human posture and perception while standing

Daniel L. Wardman, Janet L. Taylor and Richard C. Fitzpatrick

This study examines three hypotheses that have been proposed to explain the effects of galvanic vestibular stimulation (GVS) in standing human subjects. The first assumes realignment to an altered representation of vertical. GVS-evoked body tilt produced under conditions of different stability was compared with perceptions of the vertical which subjects indicated by two means, a visual line and a manipulandum. GVS produced body tilt that increased in unstable conditions but there were no differences in the perceived vertical in any condition. The second hypothesis is that the altered vestibular signal is interpreted as a tilt of the support surface. The postural response evoked by tilting the support surface was compared with the GVS response under conditions of varying stability. These responses were different, particularly for the lower body where movements were oppositely directed. Standing on foam augmented GVS responses whereas standing with feet apart augmented platform-tilt responses. The third hypothesis is that GVS produces an illusion of movement, and this causes a reaction in the opposite direction. Perception of movement during GVS was determined in standing and immobilised subjects. Although immobilised subjects experienced illusions of movement in the direction opposite the sway response, this only happened after long periods of stimulation and never for standing where subjects accurately reported the true direction of sway. Thus, the results do not support any of these proposals. Instead, they and other observations support a simpler interpretation that the GVS signal is consistent with head movement and evokes an automated response to stabilise the head in space.

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