[Effects of optokinetic stimulation on head movement and body sway of children]

We evaluated the effects of horizontal and vertical optokinetic stimulation on head movement (HM) and body sway (BS) in children and adults, using a Jung type optokinetic stimulator, a strain gauge-platform, and a encephalography. Twenty healthy children aged 7 to 9 years and twenty healthy adults aged 20 to 26 years were instructed to stand with feet close together on the platform with eyes open with and without optokinetic stimulation for 60 seconds. In all subjects, optokinetic stimulation significantly increased the total lengths of HM and BS. In addition, optokinetic stimulation significantly increased the areas of HM and BS in children, but not in adults. Although the ratio of the anteroposterior component to the lateral component in BS was significantly higher in children than in adults, the value of HM was not. Children exhibited a characteristic BS in which the anteroposterior swaying velocity was larger than the lateral swaying velocity. In the anteroposterior component, averaged divisional frequencies of BS were significantly larger in children than in adults. However, averaged divisional frequencies in the lateral component of BS and those in the anteroposterior and lateral components of HM did not differ between the two age groups. The ratio of the total length of HM to that of BS was significantly higher in children than in adults. These results suggest that HM and BS of children are readily affected by optokinetic stimulation, and that in children, the BS velocity in the anteroposterior direction is higher than that in the lateral direction.