Walker Mark F, Tian Jing, Shan Xiaoyan, Tamargo Rafael J, Ying Howard, Zee David S
Department of Neurology, The Johns Hopkins University School of Medicine, Baltimore, MD, USA.
J Neurophysiol. 2008 Oct;100(4):1813-23. doi: 10.1152/jn.01193.2007. Epub 2008 Jul 23.
We studied sinusoidal (SIN) and step-ramp (SR) pursuit in two rhesus monkeys, before and after surgical lesions of the cerebellar nodulus and uvula (Nod/Uv). Eye movements were recorded using the magnetic field scleral search coil method. Pursuit targets were generated by an LCD projector and back-projected onto a tangent screen in an otherwise dark room. After the Nod/Uv lesions, both monkeys showed a reduced eye velocity during downward pursuit (SIN: 42% decrease in M1, 91% decrease in M2; SR: 37% decrease in M1, 85% decrease in M2). For SR, the decrease was seen only for the closed-loop response; initial eye acceleration did not change (P>0.05). Upward pursuit gains increased for SIN (M1: 9%, M2: 11%); they decreased for SR (M1: 27%, M2: 18%), but to a lesser degree than for downward pursuit. Horizontal pursuit was little changed in M1 but was reduced in one direction in M2, the animal with the larger lesion. The deficit in downward tracking was limited to foveal pursuit; ocular following of random-dot stimuli was retained, even when the target subtended only several degrees. Our findings support a critical role for the Nod/Uv in vertical pursuit, particularly for sustained downward pursuit. Finally, in both monkeys, the lesion increased spontaneous upward ocular drift in the dark (mean prelesion, 1.43 degrees/s; postlesion, 5.92 degrees/s), suggesting a role for the Nod/Uv in holding the eyes still and in the genesis of downbeat nystagmus.
我们在两只恒河猴身上研究了正弦波（SIN）和阶梯斜坡（SR）追踪，分别在小脑蚓小结和小舌（Nod/Uv）进行手术损伤前后。使用磁场巩膜搜索线圈法记录眼动。追踪目标由液晶投影仪生成，并背投到一个黑暗房间中的切线屏上。在Nod/Uv损伤后，两只猴子在向下追踪时均表现出眼速度降低（SIN：M1降低42%，M2降低91%；SR：M1降低37%，M2降低85%）。对于SR，仅在闭环反应中出现降低；初始眼加速度未改变（P>0.05）。对于SIN，向上追踪增益增加（M1：9%，M2：11%）；对于SR，它们降低了（M1：27%，M2：18%），但降低程度小于向下追踪。M1中的水平追踪变化不大，但在损伤较大的动物M2中，水平追踪在一个方向上降低。向下追踪的缺陷仅限于中央凹追踪；即使目标仅张角几度，随机点刺激的眼球跟随仍得以保留。我们的研究结果支持Nod/Uv在垂直追踪中起关键作用，特别是在持续向下追踪方面。最后，在两只猴子中，损伤均增加了黑暗中自发的向上眼球漂移（损伤前平均为1.43度/秒；损伤后为5.92度/秒），提示Nod/Uv在保持眼球静止和下跳性眼球震颤的发生中起作用。
