Effects of unilateral superior colliculus ablation on oculomotor and vestibulo-ocular responses in the cat.
1. Unilateral lesions of the superior colliculus were made in normal cats. Following the operation, animals exhibited a typical neglect for contralateral visual space and forced circling toward the ipsilateral side. Optokinetic nystagmus was decreased for a stimulus moving toward the ipsilateral side, particularly in the temporal-to-nasal direction when the eye contralateral to the lesion was stimulated alone. -- 2. When tested in the dark, animals exhibited a strong imbalance of their vestibulo-ocular responses (VOR) to velocity steps or to sinusoidal oscillations. Rotation of the animal toward the ipsilateral side produced a VOR with a higher gain, and a shorter phase-lead than in pre-operative controls. VOR was decreased in the opposite direction to a smaller extent, however, the overall asymmetry between the two sides at the post-operative stage was about 40%. -- 3. In two animals, spontaneous nystagmus was present in the dark with the fast phase toward the ipsilateral side. -- 4. Visual suppression of VOR was abolished during ipsiversive rotation and was still present during contraversive rotation. -- 5. The effects of unilateral colliculectomy on VOR were transient. Spontaneous nystagmus disappeared in 3 days. VOR asymmetry in the dark was no longer present after 2-3 weeks. Loss of visual VOR suppression persisted for a few more days. -- 6. Superior colliculus exerts a tonic control on static and dynamic components of VOR. This control may mediate part of VOR visual modulation and provide a substitutive input for compensation of pathological VOR asymmetry.
D000818:Animals; D002415:Cats; D005133:Eye Movements; D007839:Functional Laterality; D009043:Motor Activity; D010812:Physical Stimulation; D013477:Superior Colliculi / Q000033:anatomy & histology / Q000502:physiology*; D014785:Vision, Ocular; D014796:Visual Perception