Effect of otolith end organ ablation on pendular rotation nystagmus in squirrel monkeys

Abstract
Summary Damped pendular rotation nystagmus was studied in squirrel monkeys before and after otolith end organ ablation (two-stage operations). After each operation, the nystagmic slow phase eye speed toward the operated side was reduced (to about 73% of that before the operation) and that to the nonoperated side did not show any marked change. A few subjects showed spontaneous nystagmus with amphetamine administration but only in dark (could not be found in light) immediately after the operation, and it disappeared rapidly. Therefore, this post-ablative reduction of the slow phase eye speed is considered to result from the loss of inputs from the otolith end organs.