Fletcher W A, Hain T C, Zee D S
Department of Neurology, Johns Hopkins University, School of Medicine, Baltimore, MD 21205.
Exp Brain Res. 1990;81(1):46-52. doi: 10.1007/BF00230099.
In four normal human subjects we measured eye movements during full-field optokinetic stimulation (10-220 deg/s) and determined the relationship among retinal-slip velocity (drum velocity minus slow-phase eye velocity), the slow-phase velocity of optokinetic nystagmus (OKN) and the initial value of the slow-phase velocity of optokinetic afternystagmus (OKAN) measured in darkness. OKN and OKAN were maximum (63-84 and 11-19 deg/s, respectively) when retinal slip ranged from 30-100 deg/s. For higher values of retinal slip, OKN and OKAN fell (in 3 subjects) or reached a plateau (in the fourth). The amplitude of OKAN in human beings was much less than that reported in monkeys. The shape, however, of the curve relating retinal slip to the amplitude of OKAN was similar to that of monkeys. Furthermore, in both cases the curve resembles that obtained by plotting the results of experimental recordings of neural discharge in the nucleus of the optic tract as a function of retinal slip. These results imply that the processing of visual information for generation of OKAN is similar in monkeys and human beings but that the gain of the system is much less in human beings. We also found that fixation of a small target during optokinetic stimulation nearly completely prevented the development of OKAN while fixation of a small target for short periods after optokinetic stimulation did not alter the pattern of decay of OKAN. Thus, fixation may actively prevent the coupling of visual information into the velocity-storage mechanism.
在四名正常人类受试者中，我们测量了全视野视动刺激（10 - 220度/秒）期间的眼动，并确定了视网膜滑动速度（鼓速减去慢相眼速度）、视动性眼震（OKN）的慢相速度与在黑暗中测量的视动后眼震（OKAN）慢相速度初始值之间的关系。当视网膜滑动速度在30 - 100度/秒范围内时，OKN和OKAN达到最大值（分别为63 - 84度/秒和11 - 19度/秒）。对于更高的视网膜滑动速度值，OKN和OKAN下降（在3名受试者中）或达到平台期（在第四名受试者中）。人类OKAN的幅度远小于猴子中报道的幅度。然而，视网膜滑动与OKAN幅度之间关系曲线的形状与猴子的相似。此外，在这两种情况下，该曲线类似于通过绘制视束核中神经放电实验记录结果作为视网膜滑动函数而获得的曲线。这些结果意味着，在猴子和人类中，用于产生OKAN的视觉信息处理是相似的，但人类中该系统的增益要小得多。我们还发现，在视动刺激期间固定一个小目标几乎完全阻止了OKAN的发展，而在视动刺激后短时间固定一个小目标并没有改变OKAN的衰减模式。因此，固定可能会积极阻止视觉信息与速度存储机制的耦合。
