Zele Andrew J, Vingrys Algis J
Department of Optometry and Vision Sciences, The University of Melbourne, VIC, Australia.
Vision Res. 2007 Sep;47(21):2700-13. doi: 10.1016/j.visres.2007.05.005. Epub 2007 Sep 6.
Symmetric flicker modulates about a background light level and effects no change in the time-average luminance. Rectified flicker is achieved by modulating a luminance-increment and results in both a flickering component and an increase in the time-averaged luminance (luminance-pedestal) above the adapting background light level. We studied the effect that changes in adapting light level and local luminance (within the area of the flickering target) have on thresholds. We measured thresholds for single and multiple cycles of flicker over a range of adapting light levels (Threshold versus Intensity paradigm) and defined their gain as a function of luminance-pedestal amplitude (Threshold versus Amplitude paradigm). The dynamics of symmetric and rectified flicker responses were determined using a Stimulus Onset Asynchrony paradigm. The data show rectified flicker thresholds differ from symmetric flicker thresholds due to two factors that can be contrast-dependent or contrast-independent: (1) local adaptation, which varies with stimulus duration and (2) surround interactions that depend on adapting light level. The dynamics of the thresholds for symmetric and rectified flicker stimuli suggest the detection mechanisms occur early in the visual pathways, involving the magnocellular pathway.
对称闪烁围绕背景光水平进行调制，且时间平均亮度无变化。整流闪烁是通过调制亮度增量来实现的，它会产生一个闪烁分量，并使时间平均亮度（亮度基座）在适应背景光水平之上增加。我们研究了适应光水平和局部亮度（在闪烁目标区域内）的变化对阈值的影响。我们在一系列适应光水平下测量了单次和多次闪烁周期的阈值（阈值与强度范式），并将它们的增益定义为亮度基座幅度的函数（阈值与幅度范式）。使用刺激起始异步范式确定对称和整流闪烁响应的动力学。数据表明，由于两个可能依赖或不依赖对比度的因素，整流闪烁阈值与对称闪烁阈值不同：（1）局部适应，它随刺激持续时间而变化；（2）依赖于适应光水平的周边相互作用。对称和整流闪烁刺激阈值的动力学表明，检测机制在视觉通路的早期发生，涉及大细胞通路。
