University of Stirling, Department of Psychology, Stirling, FK9 4LA, Scotland, United Kingdom.
Sci Rep. 2019 Mar 5;9(1):3431. doi: 10.1038/s41598-019-39064-x.
The human visual system is often tasked with extracting image properties such as symmetry from rapidly moving objects and scenes. The extent to which motion speed and symmetry processing mechanisms interact is not known. Here we examine speed-tuning properties of symmetry detection mechanisms using dynamic dot-patterns containing varying amounts of position and local motion-direction symmetry. We measured symmetry detection thresholds for stimuli in which symmetric and noise elements either drifted with different relative speeds, were relocated at different relative temporal frequencies or were static. We also measured percentage correct responses under two stimulus conditions: a segregated condition in which symmetric and noise elements drifted at different speeds, and a non-segregated condition in which the symmetric elements drifted at two different speeds in equal proportions, as did the noise elements. We found that performance (i) improved gradually with increasing the difference in relative speed between symmetric and noise elements, but was invariant across relative temporal frequencies/lifetime duration differences between symmetric and noise elements, (ii) was higher in the segregated compared to non-segregated conditions, and in the moving compared to the static conditions. We conclude that symmetry detection mechanisms are broadly tuned to speed, with speed-selective symmetry channels combining their outputs by probability summation.
人类视觉系统经常需要从快速移动的物体和场景中提取图像属性，例如对称性。目前尚不清楚运动速度和对称性处理机制之间的相互作用程度。在这里，我们使用包含不同位置和局部运动方向对称性的动态点图案来检查对称性检测机制的速度调整特性。我们测量了刺激物的对称性检测阈值，其中对称和噪声元素以不同的相对速度漂移，以不同的相对时间频率重新定位或处于静态。我们还在两种刺激条件下测量了百分比正确响应：一种是分离条件，其中对称和噪声元素以不同的速度漂移，另一种是非分离条件，其中对称元素以相等的比例以两种不同的速度漂移，噪声元素也是如此。我们发现，性能（i）随着对称和噪声元素之间的相对速度差的增加而逐渐提高，但在对称和噪声元素之间的相对时间频率/寿命持续时间差异方面保持不变，（ii）在分离条件下比非分离条件下更高，在运动条件下比静止条件下更高。我们得出的结论是，对称性检测机制广泛地适应速度，具有速度选择性的对称性通道通过概率求和来组合它们的输出。
