Stuit Sjoerd M, Cass John, Paffen Chris L E, Alais David
Experimental Psychology, Helmholtz Institute, Utrecht University, The Netherlands.
J Vis. 2009 Oct 16;9(11):17.1-15. doi: 10.1167/9.11.17.
During binocular rivalry (BR), conflicting monocular images are alternately suppressed from awareness. During suppression of an image, contrast sensitivity for probes is reduced by approximately 0.3-0.5 log units relative to when the image is in perceptual dominance. Previous studies on rivalry suppression have led to controversies concerning the nature and extent of suppression during BR. We tested for feature-specific suppression using orthogonal rivaling gratings and measuring contrast sensitivity to small grating probes at a range of orientations in a 2AFC orientation discrimination task. Results indicate that suppression is not uniform across orientations: suppression was much greater for orientations close to that of the suppressed grating. The higher suppression was specific to a narrow range around the suppressed rival grating, with a tuning similar to V1 orientation bandwidths. A similar experiment tested for spatial frequency tuning and found that suppression was stronger for frequencies close to that of the suppressed grating. Interestingly, no tuned suppression was observed when a flicker-and-swap paradigm was used, suggesting that tuned suppression occurs only for lower-level, interocular rivalry. Together, the results suggest there are two components to rivalry suppression: a general feature-invariant component and an additional component specifically tuned to the rivaling features.
在双眼竞争（BR）期间，相互冲突的单眼图像会交替地从意识中被抑制。在图像被抑制期间，相对于图像处于感知主导时，对探测刺激的对比度敏感度降低约0.3 - 0.5对数单位。先前关于竞争抑制的研究引发了关于BR期间抑制的性质和程度的争议。我们使用正交竞争光栅并在2AFC方向辨别任务中测量在一系列方向上对小光栅探测刺激的对比度敏感度，来测试特征特异性抑制。结果表明，抑制在不同方向上并不均匀：对于接近被抑制光栅方向的方向，抑制要强得多。更高的抑制特定于被抑制竞争光栅周围的一个窄范围，其调谐类似于V1方向带宽。一个类似的实验测试了空间频率调谐，发现对于接近被抑制光栅频率的频率，抑制更强。有趣的是，当使用闪烁和交换范式时未观察到调谐抑制，这表明调谐抑制仅发生在较低水平的眼间竞争中。总之，结果表明竞争抑制有两个成分：一个一般的特征不变成分和一个专门针对竞争特征进行调谐的额外成分。
