Static roll and pitch in the monkey: shift and rotation of Listing's plane

In three rhesus monkeys three-dimensional eye positions were measured with the dual search coil technique. Recordings of spontaneous eye movements were made in the light and in the dark, with the monkeys in different static roll or pitch positions. Eye positions were expressed as rotation vectors. In all static positions eye rotation vectors were confined to a plane, i.e. Listing's plane was conserved. Tilt about the roll axis shifted the plane along this axis, i.e. a constant torsional component was added to all eye positions. Tilt about the pitch axis changed the pitch angle of Listing's plane.