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, 1968?and?Naito et al., 2007) (see Section 2). The OSI takes values between 0 and 1, with 0 meaning equally responsive to all eight orientations tested and 1 meaning selective to only one of the eight. Fig. 1B shows examples of orientation tuning curves for four LGN neurons (X-cells, Cell 2, Cell 3, and Cell 4; Y-cell, Cell 1). Under optimal spatial frequency and optimal size condition (Fig. 1B, leftmost column), no cells showed significant orientation selectivity (OSI?>?0.1; Rayleigh's test, p?www.selleckchem.com/products/BIBF1120.html left), only Cell 1 exhibited significant orientation selectivity. At high spatial frequency and optimal size ( Fig. 1B, second column from right), Cells 1�C3 exhibited significant orientation tuning. At high spatial frequency and large size ( Fig. 1B, rightmost column), all four neurons showed their strongest orientation tuning. Fig. 2 summarizes the effects of spatial frequency and stimulus size on orientation selectivity in LGN neurons (N?=?87). At optimal spatial frequency and size, only 18.4% (16/87) of neurons exhibited significant orientation selectivity ( Fig. 2, leftmost); at optimal spatial frequency and large size, 25.3% (22/87) exhibited significant orientation selectivity ( Fig. 2, second from left); at high spatial frequency and optimal size, 62.1% (54/87) exhibited significant orientation selectivity ( Fig. 2, second GS-7340 cell line from right); and at high spatial frequency and large size, 93.1% (81/87) of LGN neurons exhibited significant orientation selectivity ( Fig. 2, rightmost). Statistical analysis revealed that increasing both stimulus size and spatial frequency significantly sharpened orientation tuning in the LGN (repeated two-way ANOVA; N?=?87; spatial frequency, p?Adenylyl cyclase in LGN neurons. Furthermore, the significant interaction between spatial frequency and stimulus size indicates that enlarging the stimulus size enhances orientation tuning in LGN neurons at high spatial frequency more than it does at optimal spatial frequency. In contrast, there was no significant difference in the OSI between the two cell types (X-cells, N?=?63, mean OSI?=?0.22; Y-cells, N?=?24, mean OSI?=?0.25; Wilcoxon rank sum test, p?=?0.47) and the two layers (Layer A, N?=?50, mean OSI?=?0.22; Layer A1, N?=?37, mean OSI?=?0.25; Wilcoxon rank-sum test, p?=?0.37) when tested under high spatial frequency and large size. Next, we examined the relationship between the stimulus orientation and stimulus-size tuning. Fig.