Izmaĭlov Ch A, Zimachev M M
Zh Vyssh Nerv Deiat Im I P Pavlova. 2010 Sep-Oct;60(5):615-31.
The frog retina was stimulated with light flashes homogeneous in space but not time. The time heterogeneity of stimulation was created by abrupt change of a referent stimulus for a stimulus with different luminance. Such changes form a time pattern, as well as sharp borders of luminance between the neighbor areas of the visual field form a spatial pattern. The electroretinogram recorded in response to presentation of a triad of stimuli: the onset of a short flash of homogeneous light after long dark (or light) adaptation of a retina, brief sequence of the referent and test light flashes varied in luminance, and the offset, with returning to the initial level of adaptation. It was shown that responses of the retina under conditions of time heterogeneity of stimulation could be divided in two types as well as under conditions of spatial heterogeneity. Such a dual change in amplitude confirms our earlier hypothesis on the existence of two mechanisms of luminance coding in the frog retina. The first mechanism encodes power characteristics of light, it forms the information on the absolute level of the environmental luminance. Its activity is connected basically with receptors and cells of the external plexiform layer of the frog's retina. It is responsible for the b-wave of the electroretinogram. The other mechanism associated with RERG is based on a vector code of stimuli. This mechanism forms the information on spatial and time differentiation of the light flow in the visual field and is connected basically with cells of the internal plexiform layer. The results suggest that the frog retina has the individual mechanism for time pattern detection, distinguishing it from the homogeneous light flow in a similar way as in case of spatial light pattern detection. It is possible that the first mechanism is responsible for the detection of any new stimulus in general, irrespective of its specificity, whereas the second mechanism serves for the measurement of suprathreshold differences between stimuli.
用空间均匀但时间不均匀的闪光刺激青蛙视网膜。刺激的时间不均匀性是通过将参照刺激突然改变为具有不同亮度的刺激而产生的。这种变化形成了一种时间模式，就像视野相邻区域之间亮度的清晰边界形成了一种空间模式一样。记录了对一组三联刺激的视网膜电图：在视网膜长时间暗（或光）适应后，均匀光短闪光的起始；参照光和测试光短闪光的亮度不同的简短序列；以及偏移，即回到初始适应水平。结果表明，在刺激时间不均匀的条件下，视网膜的反应也可以像在空间不均匀的条件下一样分为两种类型。这种幅度的双重变化证实了我们早期关于青蛙视网膜中存在两种亮度编码机制的假设。第一种机制编码光的功率特性，它形成关于环境亮度绝对水平的信息。其活动基本上与青蛙视网膜外网状层的感受器和细胞相关。它负责视网膜电图的b波。与视网膜电图相关的另一种机制基于刺激的矢量编码。这种机制形成关于视野中光流的空间和时间差异的信息，并且基本上与内网状层的细胞相关。结果表明，青蛙视网膜具有检测时间模式的独特机制，它以与检测空间光模式类似的方式将其与均匀光流区分开来。有可能第一种机制总体上负责检测任何新刺激，而不管其特异性如何，而第二种机制用于测量刺激之间的阈上差异。
