“Delayed VOR” : An Assessment of Vestibular Memory for Self Motion

This study investigates the ability of humans to use the vestibular system in "path integration" and to memorize the dis placement of the head. Human subjects were submitted, in complete darkness, to passive angular whole-body displacements about a vertical axis, inducing a vestibular stimulation. They were presented, before the rotation, a stationary visual target. During the rotation, they had to fixate a target which moved with the head. After a memorization delay of either less than 20 sec, about 1 min, or 5 min, after the end of the rotation, they were required to make an eye saccade toward the "memorized" stationary target. The results show that the amplitude of an angular dis placement detected by the vestibular system can be estimated and correct1y memorized du ring 1 min. At 5 min, however, rotation angles below 25 deg are overestimated.