Hore Victoria R A, Troy John B, Eglen Stephen J
Department of Applied Mathematics and Theoretical Physics, Cambridge Computational Biology Institute, University of Cambridge, Cambridge, UK.
Vis Neurosci. 2012 Nov;29(6):283-99. doi: 10.1017/S0952523812000338. Epub 2012 Oct 30.
The receptive fields of on- and off-center parasol cell mosaics independently tile the retina to ensure efficient sampling of visual space. A recent theoretical model represented the on- and off-center mosaics by noisy hexagonal lattices of slightly different density. When the two lattices are overlaid, long-range Moiré interference patterns are generated. These Moiré interference patterns have been suggested to drive the formation of highly structured orientation maps in visual cortex. Here, we show that noisy hexagonal lattices do not capture the spatial statistics of parasol cell mosaics. An alternative model based upon local exclusion zones, termed as the pairwise interaction point process (PIPP) model, generates patterns that are statistically indistinguishable from parasol cell mosaics. A key difference between the PIPP model and the hexagonal lattice model is that the PIPP model does not generate Moiré interference patterns, and hence stimulated orientation maps do not show any hexagonal structure. Finally, we estimate the spatial extent of spatial correlations in parasol cell mosaics to be only 200-350 μm, far less than that required to generate Moiré interference. We conclude that parasol cell mosaics are too disordered to drive the formation of highly structured orientation maps in visual cortex.
ON中心和OFF中心的伞状细胞镶嵌的感受野独立地覆盖视网膜，以确保对视觉空间进行高效采样。最近的一个理论模型用密度略有不同的噪声六边形晶格来表示ON中心和OFF中心的镶嵌。当这两个晶格叠加时，会产生远距离的莫尔干涉图案。有人认为这些莫尔干涉图案会驱动视觉皮层中高度结构化的方向图的形成。在这里，我们表明噪声六边形晶格并不能捕捉伞状细胞镶嵌的空间统计特征。一种基于局部排除区域的替代模型，称为成对相互作用点过程（PIPP）模型，所生成的图案在统计上与伞状细胞镶嵌无法区分。PIPP模型与六边形晶格模型的一个关键区别在于，PIPP模型不会产生莫尔干涉图案，因此受刺激的方向图不会显示出任何六边形结构。最后，我们估计伞状细胞镶嵌中空间相关性的空间范围仅为200 - 350μm，远小于产生莫尔干涉所需的范围。我们得出结论，伞状细胞镶嵌过于无序，无法驱动视觉皮层中高度结构化的方向图的形成。
