Zlatkova M, Vassilev A
Institute of Physiology, Bulgarian Academy of Sciences, Sofia.
Acta Physiol Pharmacol Bulg. 1991;17(2-3):47-53.
At the detection threshold, a line orientation is identified by the accuracy of 15-20 deg. Deviations from this rule are observed for short lines presented on a dim background. We checked up for one possible source of deviation: the substitution for foveal cone vision by peripheral rod vision. Long wavelength (red) light was used for the test line. In a control experiment such light did not stimulate rods. The test line was 4 min of arc long. It was presented for 20 ms on a white background of 1 or 1000 trolands and was viewed foveally. In a 2-alternative forced-choice experiment the psychometric functions for detection and orientation identification (vertical v. horizontal) were compared. In another experiment, the line was presented randomly in one of 18 orientations in the range 0-180 deg and the subject was asked to determine the orientation. In both experiments orientation perception was impaired at the dim background in comparison with the results at the bright background. This suggests that light-adaptational changes of the mechanisms responsible for orientation perception exist within the photopic vision.
在检测阈值时，线条方向的识别精度为15 - 20度。对于在暗背景上呈现的短线，会观察到偏离此规则的情况。我们检查了一个可能的偏差来源：周边视杆视觉替代中央凹视锥视觉。测试线使用长波长（红色）光。在对照实验中，这种光不会刺激视杆细胞。测试线长4分视角。它在1或1000托兰的白色背景上呈现20毫秒，并通过中央凹观察。在二选一的强制选择实验中，比较了检测和方向识别（垂直与水平）的心理测量函数。在另一个实验中，线条在0 - 180度范围内的18个方向之一中随机呈现，要求受试者确定方向。与亮背景下的结果相比，在暗背景下方向感知均受损。这表明在明视觉范围内存在负责方向感知的机制的光适应性变化。
