Vertical gaze stability in the cat: otolithic contribution

This study shows that there is an intrinsic asymmetry in the vertical vestibulo-ocular and optokinetic reflexes which is suppressed by macular activation. Conversely, asymmetry in vertical reflexes seems to be useful in maintaining head stability during displacements in the sagittal plane. This asymmetry is found also during ampullar and macular activation. Therefore, for head stability, asymmetric reflexes appear to have functional meaning to oppose the gravity force acting on the head, while it is not useful for eye reflexes because of the small influence of gravity on eye balls. In conclusion, the otolithic contribution to the vertical vestibulo-ocular reflex in cats is clearly important and is responsible for the most important differences between horizontal and vertical plane vestibular responses.