Area summation in human vision at and above detection threshold
Area summation in human vision at and above detection threshold
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DOI：
10.1098/rspb.2007.0957
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发表时间：
2007-11-22
影响因子：
4.7
通讯作者：
Summers, Robert J.
中科院分区：
文献类型：
--
作者：
Meese, Tim S.;Summers, Robert J.
视觉皮层的初始图像处理阶段非常适合对所观察的场景进行局部（分片）分析。但世界的结构以纹理和表面的形式延伸到空间上，这表明需要空间整合。大多数对比视觉模型都回避了这个过程，因为（i）检测阈值处的弱区域求和归因于概率求和（PS），并且（ii）远高于阈值的区域几乎没有或没有优势。这两种观点在这里都受到挑战。首先，它表明阈值处的结果与视网膜不均匀性、空间滤波、非线性对比度转换和加性高斯噪声的多个源之后的对比度线性求和一致。我们认为，先前研究中面积优势的阈上损失是由于基座抑制的伴随增加所致。为了克服这一困惑，设计了一种新颖的刺激类别，其中：（i）观察者在恒定的视网膜区域上操作，（ii）目标区域控制在该求和场内，以及（iii）基座的大小固定。使用这种布置，可以沿着整个掩蔽函数（包括促进区域）找到大量求和。我们的分析表明，PS 和不确定性不能解释结果，并且对比度的超阈值求和延伸到至少七个目标光栅周期。
The initial image-processing stages of visual cortex are well suited to a local (patchwise) analysis of the viewed scene. But the world's structures extend over space as textures and surfaces, suggesting the need for spatial integration. Most models of contrast vision fall shy of this process because (i) the weak area summation at detection threshold is attributed to probability summation (PS) and (ii) there is little or no advantage of area well above threshold. Both of these views are challenged here. First, it is shown that results at threshold are consistent with linear summation of contrast following retinal inhomogeneity, spatial filtering, nonlinear contrast transduction and multiple sources of additive Gaussian noise. We suggest that the suprathreshold loss of the area advantage in previous studies is due to a concomitant increase in suppression from the pedestal. To overcome this confound, a novel stimulus class is designed where: (i) the observer operates on a constant retinal area, (ii) the target area is controlled within this summation field, and (iii) the pedestal is fixed in size. Using this arrangement, substantial summation is found along the entire masking function, including the region of facilitation. Our analysis shows that PS and uncertainty cannot account for the results, and that suprathreshold summation of contrast extends over at least seven target cycles of grating.