The influence of gravity on vestibular nystagmus in humans.

Traditionally the human vestibular system is tested by accelerations and decelerations in a rotating chair, stimulating the horizontal semicircular canals. This kind of testing provides no information about the performance or the two pairs of vertical (anterior and posterior) canals and the two pairs of otoliths. Testing the vestibulo-ocular reflex (VOR) in its entirety requires rotations around the 3 axis of the head (yaw, pitch and roll) as well as rotations where the axis is not aligned with gravity. The data presented here are, to our knowledge, the first measurements of the VOR in normal humans obtained with 3-dimensional high resolution recording techniques.