Nishida S, Motoyoshi I, Takeuchi T
Human and Information Science Research Laboratory, NTT Communication Science Laboratories, Kanagawa, Japan.
Vision Res. 1999 Oct;39(21):3592-601. doi: 10.1016/s0042-6989(99)00046-2.
We investigated whether the size aftereffect (apparent spatial-frequency shift after adaptation to slightly different frequencies) is direction selective; i.e., whether it is stronger for test stimuli moving in the adapting direction than the opposite direction. We used drifting sinusoidal gratings of various spatiotemporal frequencies for both adaptation and test stimuli, and the perceived test frequency was estimated by means of a matching technique with a staircase method. For the purpose of comparison, the post-adaptation threshold elevation was measured in addition to the size aftereffect. The results revealed that the direction of stimuli had no influence on the magnitude of the size aftereffect for a wide range of spatiotemporal frequencies, whereas the post-adaptation threshold elevation showed clear direction selectivity. Although there was a significant direction selectivity for the size aftereffect at low spatial and high temporal frequencies, the selectivity was much weaker than that seen in the threshold elevation data. These findings are discussed in relation to the validity of a unified account of selective adaptation at and above threshold contrast and the notion of the separate processing of pattern and motion information.
我们研究了大小后效（适应于稍有不同频率后出现的明显空间频率偏移）是否具有方向选择性；也就是说，对于沿适应方向移动的测试刺激，其大小后效是否强于沿相反方向移动的测试刺激。我们对适应刺激和测试刺激均使用了各种时空频率的漂移正弦光栅，并通过带有阶梯法的匹配技术来估计感知到的测试频率。为作比较，除了大小后效外，还测量了适应后的阈值升高情况。结果显示，对于广泛的时空频率范围，刺激方向对大小后效的幅度没有影响，而适应后的阈值升高则表现出明显的方向选择性。虽然在低空间频率和高时间频率下大小后效存在显著的方向选择性，但该选择性比阈值升高数据中的选择性要弱得多。我们结合在阈值对比度及以上水平的选择性适应统一解释的有效性以及模式和运动信息的单独处理概念对这些发现进行了讨论。
