[The effect of posterior-neck-muscle vibration on apparent straight-ahead and visual localization of targets]

We examined the time course of apparent motion and apparent displacement of a visual target, and also the horizontal deviation of apparent straight-ahead related to left-posterior neck-muscle vibration. In Experiment 1, eight observers verbally judged the apparent motion and displacement of a visual target for 60 s from prior to the vibration to after its offset. We found that rightward apparent motion was an almost identical in magnitude during the vibration and disappeared within 20 s after the vibration offset. In contrast, rightward apparent displacement gradually increased during the vibration, and was sustained over 40 s after the vibration offset. In Experiment 2, five observers manually pointed to the position of a visual point in the median plane; the mean pointed position in the vibration condition was found to deviate maximally 3 degrees to the right of the mean pointed position in the control condition. In Experiment 3, the same observers closed their eyes and pointed to the apparent straight-ahead; the mean pointed positions did not differ between the vibration and control conditions.