McCourt M E, Kingdom F A
Department of Psychology, North Dakota State University, Fargo 58105-5075, USA.
Vision Res. 1996 Aug;36(16):2563-73. doi: 10.1016/0042-6989(95)00244-8.
Grating induction causes a homogeneous test field surrounded by sinewave gratings to possess an induced counterphase grating [McCourt M. E. (1982). Vision Research, 22, 119]. There is currently no consensus about the stage of visual processing at which illusory phenomena such as simultaneous brightness contrast are signaled. We measured the masking efficacy of induced gratings by measuring contrast detection thresholds for targets (sinewave luminance gratings) added in phase to both real and induced gratings which were matched in apparent contrast. At spatial frequencies below c. 0.5 c/deg, target detection and discrimination were comparably facilitated by both real and induced low-contrast pedestals (0.5-2%). At higher spatial frequencies (above 1.0 c/deg) facilitation continued to be observed for targets added in-phase to real grating pedestals, but occurred only for targets added out-of-phase with induced pedestal gratings. Higher inducing frequencies by themselves were not responsible for the observed phase shift of facilitation, however, since both real and induced pedestals produced similar target contrast discrimination functions when inducing frequency was varied by manipulating viewing distance (which holds the ratio of inducing grating period and test field height constant). The results imply the existence of at least two types of lateral interactive processes: one producing in-phase facilitation, and a second producing out-of-phase facilitation. The relative contribution of each process depends upon the ratio of inducing grating period and test field height.
光栅诱导会使被正弦波光栅包围的均匀测试场拥有一个诱导的反相光栅[麦考特·M·E.（1982年）。《视觉研究》，22卷，第119页]。目前，对于诸如同时性亮度对比等虚幻现象在视觉处理的哪个阶段发出信号，尚无共识。我们通过测量添加到具有表观对比度匹配的真实光栅和诱导光栅上的目标（正弦波亮度光栅）的对比度检测阈值，来测量诱导光栅的掩蔽效果。在空间频率低于约0.5周/度时，真实和诱导的低对比度基座（0.5 - 2%）对目标检测和辨别都有同等程度的促进作用。在较高空间频率（高于1.0周/度）时，与真实光栅基座同相添加的目标仍能观察到促进作用，但仅在与诱导基座光栅异相添加的目标上出现促进作用。然而，较高的诱导频率本身并非观察到的促进作用相移的原因，因为当通过改变观察距离（这使诱导光栅周期与测试场高度的比值保持恒定）来改变诱导频率时，真实和诱导基座产生的目标对比度辨别函数相似。结果表明至少存在两种类型的侧向交互过程：一种产生同相促进作用，另一种产生异相促进作用。每个过程的相对贡献取决于诱导光栅周期与测试场高度的比值。
