Hankins M W, Jones R J, Ruddock K H
Ruddock-Svaetichin Laboratory, Department of Physics, Imperial College, Silwood Park, Ascot, Berkshire, UK.
Vis Neurosci. 1998 Jan-Feb;15(1):55-67. doi: 10.1017/s0952523898151118.
Photopic electroretinograms (ERGs) elicited by light flashes were recorded for three normal human subjects who were exposed, throughout, to natural ambient light cycles over 24-h day-night periods. ERGs were recorded either with the adaptation state of the eyes maintained at the level set by the natural ambient lighting, or after 10 min dark adaptation. The amplitudes and implicit times of both the a- and b-wave components of the ERG were examined and of these, only the b-wave implicit time exhibited significant diurnal variation, such that the nighttime values were 20-40% greater than those recorded during daytime. Such diurnal variations were observed under both recording conditions and cannot, therefore, be attributed to diurnal changes in the adaptation state of the cone photoreceptors. ERGs were recorded at midday and midnight during 24-h exposure to the natural light cycle, but during the recording period, the short-term adaptation state of the eye was controlled by exposure to rod saturating background field, so that visual sensitivity was the same at both recording times. The b-wave implicit times recorded at midnight were, nonetheless, greater than those recorded at midday. This difference is not, therefore, determined by the short-term state of retinal adaptation, but reflects long-term light history. Measurements performed under 24-h continuous light exposure showed no variation in the b-wave implicit time, whereas some measurements made during extended dark adaptation provided limited evidence for implicit time changes. By controlling the wavelengths to which the eye was exposed during the daylight phase of the diurnal cycle, it was shown that the shifts in b-wave implicit time associated with the change from dark to light are triggered by the rod system, although they are most clearly observed in the cone-dominant responses to long-wavelength light. The results demonstrate a diurnal variation in the temporal responses of the post-photoreceptoral cone pathways of the human retina, which is triggered by activation of the rod photoreceptors.
对三名正常人类受试者记录了由闪光诱发的明视视网膜电图（ERG），这些受试者在整个24小时昼夜周期内都暴露于自然环境光周期中。ERG记录时，眼睛的适应状态要么保持在自然环境光照设定的水平，要么在暗适应10分钟后进行。对ERG的a波和b波成分的振幅和隐含时间进行了检查，其中只有b波隐含时间表现出显著的昼夜变化，夜间值比白天记录的值大20 - 40%。在两种记录条件下均观察到这种昼夜变化，因此不能归因于视锥光感受器适应状态的昼夜变化。在24小时暴露于自然光周期的过程中，于中午和午夜记录ERG，但在记录期间，眼睛的短期适应状态通过暴露于使视杆细胞饱和的背景场来控制，以便在两个记录时间的视觉敏感度相同。尽管如此，午夜记录的b波隐含时间仍大于中午记录的时间。因此，这种差异不是由视网膜适应的短期状态决定的，而是反映了长期的光照经历。在24小时持续光照下进行的测量显示b波隐含时间没有变化，而在长时间暗适应期间进行的一些测量提供了隐含时间变化的有限证据。通过在昼夜周期的白天阶段控制眼睛暴露的波长，结果表明与从暗到光的变化相关的b波隐含时间的变化是由视杆系统触发的，尽管它们在对长波长光的视锥主导反应中最明显地观察到。结果表明，人类视网膜光感受器后视锥通路的时间反应存在昼夜变化，这是由视杆光感受器的激活触发的。
