Johnston A, Wright M J
Vision Res. 1985;25(2):179-85. doi: 10.1016/0042-6989(85)90111-7.
We investigated the lower threshold for motion (LTM) of gratings as a function of position in the visual field, spatial frequency and contrast and we compared motion thresholds for sine wave and square wave luminance profiles. For contrasts below 0.05 the lower threshold for motion was raised; the increase in threshold being dependent upon spatial frequency. At contrast levels above 0.05, LTM was found to be a constant velocity at any given spatial location but increased with eccentricity of view. Raised thresholds for motion at eccentric locations could be compensated by increasing the size of eccentric gratings in proportion to M-1, where M is the cortical magnification factor, a procedure which standardises the cortical representation at differing eccentricities. Thus LTM could be expressed as a constant cortical velocity for grating contrasts above 0.05 at all stimulus locations investigated. We interpret our data as support for a ratio model of velocity coding.
我们研究了光栅运动的下限阈值（LTM）作为视野位置、空间频率和对比度的函数，并比较了正弦波和方波亮度分布的运动阈值。对于对比度低于0.05的情况，运动下限阈值升高；阈值的增加取决于空间频率。在对比度高于0.05的水平下，发现LTM在任何给定空间位置是一个恒定速度，但随着视野偏心度增加。偏心位置处运动阈值的升高可以通过将偏心光栅的尺寸按M-1比例增加来补偿，其中M是皮质放大因子，该过程使不同偏心度处的皮质表征标准化。因此，在所有研究的刺激位置，对于对比度高于0.05的光栅，LTM可以表示为恒定的皮质速度。我们将我们的数据解释为对速度编码比率模型的支持。
