Changes in control of eye movement and upper limb movement with automatization of postural control during floor vibration

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We investigated changes in control of the eye movement and upper limb movement with automatization of postural control during floor vibration. The subjects were healthy university students, all of them had no experience of floor vibration. The saccadic eye movement (S-group, n=9) and smooth pursuit eye movement (P-group, n=10) were adopted as the eye movement. The reaction movement (R-group, n=10) and tracking movement (T-group, n=10) were adopted as the upper limb movement. A vibration table mounted with a force platform was vibrated sinusoidaly in anteroposterior direction under the condition of 2.5 cm amplitude and 0.5 Hz frequency. A visual target was presented on a face mounting display. The movement of the eye and upper limb were picked up using the electro-oculogram technique and electric signal of a potentiometer that was controlled by the upper limb, respectively. For T-group, a spot for following the visual target, which was controlled by the electric signal of potentiometer, … More was presented on the face mounting display. The visual target was alternately moved toward left and right for random durations of 2-4 s for S- and R-groups, and was moved sinusoidaly in horizontal level under the condition of 0.3 Hz for P- and T-groups. A visual angle was set at 20 degree. The eye movement or upper limb movement was measured (Control) after the training session for each movement. After that the floor vibration for 1 minute was repeated 11 times. The eye movement or upper limb movement was simultaneously performed in the 1st and llth trials.For all subject-groups, the mean speed of the fluctuation of center of foot pressure decreased in initial trials, while after that it was constantly maintained till the 10th trial. The mean speed in the llth trial was significantly increased relative to that in the 10th trial for all subject-groups except S-group. This increase was significantly greater for T-group than for R-group. The eye movement performance of the 1st trial in only for S-group was inferior to that of Control and the llth trial. A similar phenomenon was found in the performance of the upper limb movement for R- and T-groups. These results suggest that (1) simultaneous postural control with the eye movement or the upper limb movement improves with automatization of postural control, (2) the large interference occurs when the more voluntary movement was simultaneously performed with postural control. Less