Eiber C D, Pietersen A N J, Zeater N, Solomon S G, Martin P R
Save Sight Institute, University of Sydney, Sydney, Australia; School of Medical Sciences, University of Sydney, Sydney, Australia; Australian Research Council Centre of Excellence for Integrative Brain Function, University of Sydney, Australia.
School of Medical Sciences, University of Sydney, Sydney, Australia; Department of Experimental Psychology, University College London, United Kingdom.
Vision Res. 2018 Oct;151:41-52. doi: 10.1016/j.visres.2017.09.002. Epub 2017 Nov 22.
The "blue-on" and "blue-off" receptive fields in retina and dorsal lateral geniculate nucleus (LGN) of diurnal primates combine signals from short-wavelength sensitive (S) cone photoreceptors with signals from medium/long wavelength sensitive (ML) photoreceptors. Three questions about this combination remain unresolved. Firstly, is the combination of S and ML signals in these cells linear or non-linear? Secondly, how does the timing of S and ML inputs to these cells influence their responses? Thirdly, is there spatial antagonism within S and ML subunits of the receptive field of these cells? We measured contrast sensitivity and spatial frequency tuning for four types of drifting sine gratings: S cone isolating, ML cone isolating, achromatic (S + ML), and counterphase chromatic (S - ML), in extracellular recordings from LGN of marmoset monkeys. We found that responses to stimuli which modulate both S and ML cones are well predicted by a linear sum of S and ML signals, followed by a saturating contrast-response relation. Differences in sensitivity and timing (i.e. vector combination) between S and ML inputs are needed to explain the amplitude and phase of responses to achromatic (S + ML) and counterphase chromatic (S - ML) stimuli. Best-fit spatial receptive fields for S and/or ML subunits in most cells (>80%) required antagonistic surrounds, usually in the S subunit. The surrounds were however generally weak and had little influence on spatial tuning. The sensitivity and size of S and ML subunits were correlated on a cell-by-cell basis, adding to evidence that blue-on and blue-off receptive fields are specialised to signal chromatic but not spatial contrast.
昼行性灵长类动物视网膜和背外侧膝状核（LGN）中的“开蓝”和“关蓝”感受野将来自短波敏感（S）锥光感受器的信号与来自中/长波敏感（ML）光感受器的信号结合起来。关于这种结合存在三个尚未解决的问题。首先，这些细胞中S和ML信号的结合是线性的还是非线性的？其次，S和ML输入到这些细胞的时间如何影响它们的反应？第三，这些细胞感受野的S和ML亚单位内是否存在空间拮抗作用？我们在狨猴LGN的细胞外记录中，测量了四种类型的漂移正弦光栅的对比度敏感度和空间频率调谐：S锥隔离光栅、ML锥隔离光栅、消色差（S + ML）光栅和反相色（S - ML）光栅。我们发现，对同时调制S和ML锥的刺激的反应，可以通过S和ML信号的线性总和，再加上饱和的对比度-反应关系，得到很好的预测。需要S和ML输入之间的敏感度和时间差异（即矢量组合）来解释对消色差（S + ML）和反相色（S - ML）刺激的反应的幅度和相位。大多数细胞（>80%）中S和/或ML亚单位的最佳拟合空间感受野需要拮抗周边，通常是在S亚单位中。然而，这些周边通常较弱，对空间调谐的影响很小。S和ML亚单位的敏感度和大小在逐个细胞的基础上相关，这进一步证明了“开蓝”和“关蓝”感受野专门用于信号颜色对比度而非空间对比度。
