McAnany J Jason, Alexander Kenneth R
Department of Ophthalmology & Visual Sciences, University of Illinois at Chicago, 1855 W. Taylor St., Chicago, IL 60612, USA.
Vision Res. 2009 May;49(11):1389-96. doi: 10.1016/j.visres.2008.10.012. Epub 2009 Apr 7.
This study investigated the way in which the temporal properties of additive luminance noise influence threshold contrast and affect estimates of equivalent noise and sampling efficiency. Threshold contrast was obtained from four visually normal observers for a 2-cycle-per-degree Gabor patch across a range of target durations in the absence and presence of additive luminance noise that was either static or dynamic. In addition, the temporal relationship between target and noise was either synchronous (simultaneous presentation of both) or asynchronous (noise duration longer than target duration). For both synchronous and asynchronous presentation modes, the extent of temporal integration differed for targets presented in dynamic vs. static noise. Furthermore, for a fixed-duration target, increasing the degree of temporal asynchrony between target and noise monotonically increased threshold contrast in dynamic noise, but had a non-monotonic effect on threshold contrast in static noise. For both dynamic and static noise, estimates of equivalent noise and sampling efficiency were dependent on the degree of temporal asynchrony between target and noise. The observed differences between the effects of dynamic and static noise are consistent with a previous proposal that detection of targets of intermediate spatial frequency in the presence of these two noise types is governed by sustained-like and transient-like visual mechanisms, respectively.
本研究调查了加性亮度噪声的时间特性影响阈值对比度以及对等效噪声和采样效率估计的方式。在不存在和存在静态或动态加性亮度噪声的情况下，从四名视力正常的观察者那里获得了针对每度2个周期的Gabor斑块在一系列目标持续时间下的阈值对比度。此外，目标与噪声之间的时间关系要么是同步的（两者同时呈现），要么是异步的（噪声持续时间长于目标持续时间）。对于同步和异步呈现模式，在动态噪声与静态噪声中呈现的目标，其时间整合程度有所不同。此外，对于固定持续时间的目标，增加目标与噪声之间的时间异步程度会使动态噪声中的阈值对比度单调增加，但对静态噪声中的阈值对比度有非单调影响。对于动态和静态噪声，等效噪声和采样效率的估计均取决于目标与噪声之间的时间异步程度。动态噪声和静态噪声效应之间观察到的差异与之前的一项提议一致，即在这两种噪声类型存在的情况下，对中等空间频率目标的检测分别由类似持续和类似瞬态的视觉机制控制。
