Maddess T, Ibbotson M R
Centre for Visual Science, Research School of Biological Sciences, Australian National University, Canberra.
Exp Brain Res. 1992;91(3):525-38. doi: 10.1007/BF00227849.
Optokinetic nystagmus (OKN) induced by wide-field visual stimulation was measured with and without prior adaptation to moving sinusoidal gratings. Under unadapted conditions the mean gains of the slow phases of OKN in the first 500 ms were 0.5-0.8, and the eye velocities and amplitudes had rise times with time constants of 0.1-0.2 s. By contrast, following adaptation to as little as 1 s of image motion, the magnitude of the initial gains fell and the rise times of the velocities and amplitudes increased markedly. The degree of adaptation depended on the adapting temporal frequency, the optimum adaptive frequencies being 1.7-3.4 Hz. In this range of temporal frequencies, the initial gains fell to 0.1-0.3 and the rise times for velocity and amplitude ranged from 0.4 to 7.0 s, depending on the length of the adapting period. Thus the observed changes in the time constant were up to 70-fold. Neither spatial frequency or image velocity had any marked influence on the level of adaptation. The dependence on temporal frequency rather than image velocity suggests that the motion detectors feeding the adaptive system respond to local motion-related changes in luminance. The adaptive effects were direction-selective, showing that this must also be the case for the motion detectors. The adaptive effects were observed both when the drift temporal frequency on the retina was established by artificially maintaining a fixed gaze or when the adapting temporal frequency was induced by retinal slip during OKN. Time constants for recovery from adaptation were similar to motion aftereffects measured by psychophysical and physiological methods. The results suggest a link between cortical motion adaptation and adaptive mechanisms effecting the oculomotor system.
在有或没有事先适应移动正弦光栅的情况下，测量了由宽视野视觉刺激诱发的视动性眼震（OKN）。在未适应的条件下，OKN慢相在前500毫秒的平均增益为0.5 - 0.8，眼速度和振幅的上升时间的时间常数为0.1 - 0.2秒。相比之下，在仅适应1秒图像运动后，初始增益的幅度下降，速度和振幅的上升时间显著增加。适应程度取决于适应的时间频率，最佳适应频率为1.7 - 3.4赫兹。在这个时间频率范围内，初始增益降至0.1 - 0.3，速度和振幅的上升时间根据适应期的长度在0.4至7.0秒之间。因此，观察到的时间常数变化高达70倍。空间频率或图像速度对适应水平均无明显影响。对时间频率而非图像速度的依赖表明，为自适应系统提供信息的运动探测器对与局部运动相关的亮度变化做出反应。自适应效应具有方向选择性，这表明运动探测器也必然如此。无论是通过人为保持固定注视来确定视网膜上的漂移时间频率，还是在OKN期间由视网膜滑动诱发适应时间频率时，都观察到了自适应效应。适应恢复的时间常数与通过心理物理学和生理学方法测量的运动后效应相似。结果表明皮质运动适应与影响动眼系统的自适应机制之间存在联系。
