Head and body sway in response to vertical visual stimulation.
CONCLUSIONS
Postural responses differed according to the stimulus direction, i.e. vertical visual stimulation induced head rather than trunk displacements. Accordingly, it could be that center of foot pressure (COP) responses tended to underestimate the postural sway during visual stimulation.


OBJECTIVE
To investigate head and body sway in response to vertical visual surround motion, and to examine the correlation between the displacements of head and body segments derived from video-motion analysis and COP measurements.


METHODS
Postural sway was assessed in 10 young female subjects by video-motion analysis of four different head and body segments, and by use of force-plate posturography. Head and body sway in the pitch plane was induced by rotating a random pattern of dots about the subject's inter-aural axis at a constant acceleration of 1 degree/s(2) or a constant velocity of 60 degrees/s in darkness.


RESULTS
Generally, head displacement was greater than that of other body parts during vertical optokinetic stimulation (OKS). In most subjects, maximum head displacements were induced in the same direction as the visual motion. Downward OKS induced a forward head and body sway. The COP trajectory correlated well with the displacements of each head and body segment during downward OKS. In contrast, postural responses to upward OKS were complicated in terms of their time course. The correlation coefficient between each head and body segment and the COP varied among individuals for upward OKS.
Kobayashi
Kenji
K
Department of Otolaryngology, Toyama Medical and Pharmaceutical University, Toyama, Japan.
Fushiki
Hiroaki
H
Asai
Masatsugu
M
Watanabe
Yukio
Y
D000328:Adult; D005260:Female; D006801:Humans; D010775:Photic Stimulation / Q000379:methods*; D004856:Postural Balance; D011187:Posture / Q000502:physiology*; D014743:Videotape Recording; D014796:Visual Perception / Q000502:physiology*