Detection of Gabor patterns of different sizes, shapes, phases and eccentricities
Detection of Gabor patterns of different sizes, shapes, phases and eccentricities
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DOI：
10.1016/j.visres.2006.09.005
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发表时间：
2007-01-01
期刊：
影响因子：
1.8
通讯作者：
Farias, Mylene C. Q.
中科院分区：
文献类型：
--
作者：
Foley, John M.;Varadharajan, Srinivasa;Farias, Mylene C. Q.
使用2AFC方法测量垂直Gabor模式的对比度阈值，作为其偏心，大小，形状和相位的函数。图案为4℃/度，呈现时间为90 ms或240 ms。对数阈值以0.47 dB/波长的平均速率随偏心率线性增加。对于以中央凹为中心的图案，阈值随着图案面积在12个波长的整个标准偏差范围内的增加而降低。TvA函数在log - log坐标上向上凹。对于小的图案，形状和大小之间的相互作用取决于相位。阈值对比能量是面积的u形函数，最小值在0.4波长附近，表明检测到小的感受野。当模式处于阈值时，观察者可以区分不同大小的模式，表明涉及不止一种机制。结果是由一个模型来解释的，在这个模型中，图案激发了一组稍微延长的接受野，除了它们的灵敏度随偏心率呈指数级下降外，它们是相同的。激发被提升到一个幂次，然后在接受野上线性求和以确定阈值。结果同样很好地描述了内部噪声限制模型。TvA函数不足以单独估计噪声和幂函数的指数。然而，一项实验表明，试验序列内的混合大小对阈值没有影响，这表明限制噪声不会随着监测机制的数量而增加。(c) 2006 Elsevier Ltd.版权所有。
Contrast thresholds of vertical Gabor patterns were measured as a function of their eccentricity, size, shape, and phase using a 2AFC method. The patterns were 4 c/deg and they were presented for 90 or 240 ms. Log thresholds increase linearly with eccentricity at a mean rate of 0.47 dB/wavelength. For patterns centered on the fovea, thresholds decrease as the area of the pattern increases over the entire standard deviation range of 12 wavelengths. The TvA functions are concave up on log log coordinates. For small patterns there is an interaction between shape and size that depends on phase. Threshold contrast energy is a U-shaped function of area with a minimum in the vicinity of 0.4 wavelength indicating detection by small receptive fields. Observers can discriminate among patterns of different sizes when the patterns are at threshold indicating that more than one mechanism is involved. The results are accounted for by a model in which patterns excite an array of slightly elongated receptive fields that are identical except that their sensitivity decreases exponentially with eccentricity. Excitation is raised to a power and then summed linearly across receptive fields to determine the threshold. The results are equally well described by an internal-noise-limited model. The TvA functions are insufficient to separately estimate the noise and the exponent of the power function. However, an experiment that shows that mixing sizes within the trial sequence has no effect on thresholds, suggests that the limiting noise does not increase with the number of mechanisms monitored. (c) 2006 Elsevier Ltd. All rights reserved.