Ocular torsion produced by unilateral chemical inactivation of the cerebellar flocculus in alert cats.
OBJECTIVE
Vertical eye movements are executed by the vertical recti and oblique muscle pairs. Since each of these pairs rotates the eye in both vertical and torsional directions, torsional components must be controlled to execute appropriate, purely vertical eye movements. To test whether the cerebellar flocculus is involved in the control of torsional eye position, we examined the effects of unilateral chemical inactivation of the flocculus on ocular torsion in alert cats.


METHODS
Pitch-responding floccular regions were first identified, then the GABA agonist muscimol was injected unilaterally into the identified regions. Ocular torsion was examined photographically.


RESULTS
Unilateral muscimol infusion into pitch-responding areas in the rostral and middle parts of the flocculus resulted in significant intorsion of the eye ipsilateral to the infusion. Gaze-holding was also impaired following downward saccades induced by visual stimuli. Although the contralateral eye showed a tendency towards extorsion, the effects were not significant. Muscimol infusion into the caudal flocculus did not induce consistent effects on ocular torsion.


CONCLUSIONS
The cerebellar flocculus plays a key role in the maintenance of torsional eye position.
Chin
Shinki
S
Department of Ophthalmology and Visual Sciences, Hokkaido University, Sapporo, Japan.
Fukushima
Kikuro
K
Fukushima
Junko
J
Kase
Manabu
M
Ohno
Shigeaki
S
D000818:Animals; D002415:Cats; D002531:Cerebellum / Q000187:drug effects / Q000502:physiology*; D005133:Eye Movements / Q000502:physiology*; D018755:GABA Agonists / Q000494:pharmacology*; D007267:Injections; D009118:Muscimol / Q000494:pharmacology*; D015835:Ocular Motility Disorders / Q000209:etiology* / Q000503:physiopathology; D009801:Oculomotor Muscles / Q000503:physiopathology*; D012399:Rotation; D014102:Torsion Abnormality
D018755:GABA Agonists; D009118:Muscimol