Regan D
J Opt Soc Am A. 1985 Jul;2(7):1153-9. doi: 10.1364/josaa.2.001153.
Spatial-frequency discrimination thresholds were measured using the temporal two-alternative forced-choice procedure. A superimposed masker grating reduced discrimination threshold more than 20-fold when the spatial frequency of the masker was close to the test spatial frequency because moiré fringes provided a sensitive cue to the test grating's spatial frequency. When the effectiveness of this cue was reduced by randomly changing the frequency of the masker grating on successive presentations, masked thresholds were found to be elevated when the masker frequency was within roughly 1 octave of the test frequency. On the other hand, postadaptation thresholds were not elevated when the test frequency was close to the adapting frequency but were elevated at about twice the adapting frequency. Thus masking and adaptation have quite different effects on spatial-frequency discrimination, though their effects on contrast sensitivity are qualitatively similar. It is proposed that discrimination is determined by opponent-size processing. Adaptation elevates discrimination threshold by reducing the sensitivity of opponent elements. The masker grating elevates threshold by increasing the noise level of opponent elements, thus reducing the precision with which the visual pathway encodes spatial frequency.
使用时间二选一强制选择程序测量空间频率辨别阈值。当掩蔽光栅的空间频率接近测试空间频率时，叠加的掩蔽光栅可将辨别阈值降低20倍以上，因为莫尔条纹为测试光栅的空间频率提供了敏感线索。当通过在连续呈现时随机改变掩蔽光栅的频率来降低该线索的有效性时，发现当掩蔽频率在测试频率的大约1个八度范围内时，掩蔽阈值会升高。另一方面，当测试频率接近适应频率时，适应后阈值不会升高，但在大约两倍适应频率时会升高。因此，掩蔽和适应对空间频率辨别有相当不同的影响，尽管它们对对比度敏感性的影响在定性上是相似的。有人提出，辨别是由对立大小处理决定的。适应通过降低对立元素的敏感性来提高辨别阈值。掩蔽光栅通过增加对立元素的噪声水平来提高阈值，从而降低视觉通路编码空间频率的精度。
