Frishman L J, Levine M W
J Physiol. 1983 Jun;339:475-94. doi: 10.1113/jphysiol.1983.sp014728.
Action potentials were recorded from single fibres in the optic tracts of anaesthetized cats. Continuous records were obtained at various levels of scotopic and mesopic retinal illumination. In some cases, the light intensity was modulated by a pseudorandom Gaussian white-noise signal. The maintained discharge of on-centre neurones increased while the maintained discharge of off-centre neurons decreased with increased illumination of the receptive field centre. For both cell types, the coefficient of variation declined with increased rate of discharge. There was minimal short-term dependency in the firing patterns, and it was unaffected by the level of retinal illumination. Virtually all of the structure revealed by the normalized autocovariance functions could be attributed to the shape of the interval distributions. The first few coefficients of the serial correlogram were slightly negative. The magnitude of this negativity was not related to illumination. Long-term dependency in the firing pattern was also quite small; the standard deviations of the mean rate in samples of about 1 sec duration were only slightly less than would be predicted from the interval distributions. This dependency tended to increase at higher retinal illuminations. Neural discharges elicited by Gaussian modulation of the light were strikingly different from those elicited by steady light. Modulation caused the first coefficient of the serial correlogram to become more positive, while the next several coefficients became more negative. A corresponding pattern could be seen in the normalized autocovariance functions, and in the differences between the normalized autocovariance and normalized autoconvolution. Long-term dependency also increased dramatically, such that the standard deviations of mean rate were about 60% of what would be expected given the interval distributions observed. These results place a number of constraints upon the ways in which intrinsic noise in the retina may enter the visual processing network. Two alternative models consistent with the data are presented.
在麻醉猫的视束中，从单根纤维记录动作电位。在不同水平的暗视和中间视觉视网膜光照条件下获得连续记录。在某些情况下，光强度由伪随机高斯白噪声信号调制。随着感受野中心光照增加，中心型神经元的持续放电增加，而外周型神经元的持续放电减少。对于这两种细胞类型，变异系数随着放电率增加而下降。放电模式中的短期依赖性最小，且不受视网膜光照水平的影响。归一化自协方差函数揭示的几乎所有结构都可归因于间隔分布的形状。序列相关图的前几个系数略为负值。这种负值的大小与光照无关。放电模式中的长期依赖性也相当小；约1秒持续时间样本中平均放电率的标准差仅略小于根据间隔分布预测的值。这种依赖性在较高视网膜光照下趋于增加。由光的高斯调制引发的神经放电与由稳定光引发的神经放电明显不同。调制使序列相关图的第一个系数变得更正，而接下来的几个系数变得更负。在归一化自协方差函数以及归一化自协方差与归一化自卷积之间的差异中可以看到相应的模式。长期依赖性也急剧增加，使得平均放电率的标准差约为根据观察到的间隔分布预期值的60%。这些结果对视网膜内在噪声进入视觉处理网络的方式施加了一些限制。提出了两个与数据一致的替代模型。
