Saccadic dysmetria and adaptation after lesions of the cerebellar cortex.
We studied the effects of small lesions of the oculomotor vermis of the cerebellar cortex on the ability of monkeys to execute and adapt saccadic eye movements. For saccades in one horizontal direction, the lesions led to an initial gross hypometria and a permanent abolition of the capacity for rapid adaptation. Mean saccade amplitude recovered from the initial hypometria, although variability remained high. A series of hundreds of repetitive saccades in the same direction resulted in gradual decrement of amplitude. Saccades in other directions were less strongly affected by the lesions. We suggest the following. (1) The cerebellar cortex is constantly recalibrating the saccadic system, thus compensating for rapid biomechanical changes such as might be caused by muscle fatigue. (2) A mechanism capable of slow recovery from dysmetria is revealed despite the permanent absence of rapid adaptation.
Barash
S
S
Department of Neurobiology, Weizmann Institute of Science, Rehovot 76100, Israel. shabtai.barash@weizmann.ac.il
Melikyan
A
A
Sivakov
A
A
Zhang
M
M
Glickstein
M
M
Thier
P
P
D000222:Adaptation, Physiological; D000818:Animals; D002524:Cerebellar Ataxia / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology*; D002525:Cerebellar Cortex / Q000473:pathology*; D002526:Cerebellar Diseases / Q000150:complications* / Q000473:pathology; D008252:Macaca fascicularis; D008297:Male; D018763:Muscle Fatigue; D009801:Oculomotor Muscles / Q000503:physiopathology; D012016:Reference Values; D012438:Saccades