Lee R J, Mollon J D, Zaidi Q, Smithson H E
Department of Psychology, Durham University, UK.
J Vis. 2009 Nov 12;9(12):5.1-17. doi: 10.1167/9.12.5.
There are many distinct types of retinal ganglion and LGN cells that have opponent cone inputs and which may carry chromatic information. Of interest are the asymmetries in those LGN cells that carry S-cone signals: in S-ON cells, S+ signals are opposed by (L + M) whereas, in many S-OFF cells, L+ signals are opposed by (S + M), giving -S + L - M (C. Tailby, S. G. Solomon, & P. Lennie, 2008). However, the S-opponent pathway is traditionally modeled as +/-[S - (L + M)]. A phase lag of the S-cone signal has been inferred from psychophysical thresholds for discriminating combinations of simultaneous sinusoidal modulations along +/-[L - M] and +/-[S - (L + M)] directions (C. F. Stromeyer, R. T. Eskew, R. E. Kronauer, & L. Spillmann, 1991). We extend this experiment, measuring discrimination thresholds as a function of the phase delay between pairs of orthogonal component modulations. When one of the components isolates the tritan axis, there are phase delays at which discrimination is impossible; when neither component is aligned with the tritan axis, discrimination is possible at all delays. The data imply that the S-cone signal is delayed by approximately 12 ms relative to (L - M) responses. Given that post-receptoral mechanisms show diverse tuning around the tritan axis, we suggest that the delay arises before the S-opponent channels are constructed, possibly in the S-cones themselves.
存在许多不同类型的视网膜神经节细胞和外侧膝状体（LGN）细胞，它们具有对立的视锥细胞输入，并且可能携带颜色信息。有趣的是，那些携带S视锥信号的LGN细胞存在不对称性：在S-ON细胞中，S+信号与（L + M）信号相对，而在许多S-OFF细胞中，L+信号与（S + M）信号相对，即-S + L - M（C. Tailby、S. G. Solomon和P. Lennie，2008年）。然而，传统上S对立通路的模型为+/-[S - (L + M)]。根据用于区分沿+/-[L - M]和+/-[S - (L + M)]方向同时进行的正弦调制组合的心理物理学阈值，推断出S视锥信号存在相位滞后（C. F. Stromeyer、R. T. Eskew、R. E. Kronauer和L. Spillmann，1991年）。我们扩展了这个实验，测量了作为正交分量调制对之间相位延迟函数的辨别阈值。当其中一个分量分离出蓝黄轴时，存在一些相位延迟使得辨别变得不可能；当两个分量都不与蓝黄轴对齐时，在所有延迟情况下都可以进行辨别。数据表明，相对于（L - M）反应，S视锥信号延迟了约12毫秒。鉴于感受器后机制在蓝黄轴周围表现出多样的调谐，我们认为这种延迟出现在构建S对立通道之前，可能就在S视锥细胞本身。
