Glasser Davis M, Tadin Duje
Center for Visual Science and Department of Brain and Cognitive Sciences, University of Rochester, Rochester, NY 14627, USA.
J Vis. 2010 Apr 28;10(4):20.1-9. doi: 10.1167/10.4.20.
Classic psychophysical studies have shown that increasing the size of low-contrast moving stimuli increases their discriminability, indicating spatial summation mechanisms. More recently, a number of studies have reported that for moderate and high contrasts, size increases yield substantial deteriorations of motion perception-a result described as psychophysical spatial suppression. While this result resembles known characteristics of suppressive center-surround neural mechanisms, a recent study (C. R. Aaen-Stockdale, B. Thompson, P. C. Huang, & R. F. Hess, 2009) argued that observed size-dependent changes in motion perception might be explained by differences in contrast sensitivity for stimuli of different sizes. Here, we tested this hypothesis using duration threshold measurements-an experimental approach used in several spatial suppression studies. The results replicated previous reports by demonstrating spatial suppression at a fixed, high contrast. Importantly, we observed strong spatial suppression even when stimuli were normalized relative to their contrast thresholds. While the exact mechanisms underlying spatial suppression still need to be adequately characterized, this study demonstrates that a low-level explanation proposed by Aaen-Stockdale et al. (2009) cannot account for spatial suppression results.
经典的心理物理学研究表明，增大低对比度移动刺激的大小会提高其可辨别性，这表明存在空间总和机制。最近，一些研究报告称，对于中等和高对比度，增大刺激大小会导致运动感知能力大幅下降——这一结果被描述为心理物理学空间抑制。虽然这一结果类似于已知的抑制性中心-外周神经机制的特征，但最近一项研究（C.R. 阿恩 - 斯托克代尔、B. 汤普森、P.C. 黄和R.F. 赫斯，2009年）认为，观察到的运动感知中与大小相关的变化可能是由不同大小刺激的对比度敏感性差异所解释的。在此，我们使用持续时间阈值测量来检验这一假设——这是在多项空间抑制研究中使用的一种实验方法。结果通过在固定的高对比度下证明空间抑制，重现了先前的报告。重要的是，即使刺激相对于其对比度阈值进行了归一化，我们仍观察到强烈的空间抑制。虽然空间抑制背后的确切机制仍需充分表征，但这项研究表明阿恩 - 斯托克代尔等人（2009年）提出的低水平解释无法解释空间抑制结果。
