Effect of light sleep on three-dimensional eye position in static roll andpitch

We examined three-dimensional eye positions in alertness and light sleep wh en monkeys were placed in different roll and pitch body orientations. In al ertness, eye positions were confined to a fronto-parallel (Listing's) plane , torsional variability was small and static roll or pitch induced a torsio nal shift or vertical rotation of these planes. In light sleep. the planes rotated temporally by about 10 degrees, torsional variability increased by a factor of two and the static otolith-ocular reflexes were reduced by abou t 70% These data support the importance of a neural control of the thicknes s and orientation of Listing's plane, and suggest that part of the vestibul ar input underlying otolith-ocular reflexes depend on polysynaptic neural p rocessing. (C) 2001 Elsevier Science Ltd. All rights reserved.