Fendick M G, Swindale N V
Department of Ophthalmology, University of British Columbia, Vancouver, Canada.
Vision Res. 1994 Oct;34(20):2717-26. doi: 10.1016/0042-6989(94)90228-3.
We investigated the effects of contrast and temporal frequency on vernier edge alignment thresholds. Edges were defined by the presence of a 180 deg phase difference in the temporal modulation waveform of adjacent rectangles with spatially uniform luminances. Thresholds of 10 arc sec or less could be obtained at high contrasts, and flicker rates up to 8 Hz. Above this range, thresholds increased rapidly with decreasing contrast and increasing rates of flicker. Thresholds also increased with increasing temporal frequency over the range 0-20 Hz for contrasts normalized to thresholds for the detection of either flicker or the edge. Linear regression on log-log plots of threshold vs contrast at different temporal frequencies showed that the relationship between threshold and contrast was well described by a power law with an exponent of about -0.5 at temporal frequencies of 8 Hz or lower. About 8 Hz the slope more than doubled and thresholds increased. Thresholds also increased when the relative phase (i.e. the instantaneous sign of the contrast) of the upper and lower edges was reversed, and this effect was observed at all temporal frequencies. Measurements of threshold as a function of the size of a gap between the upper and lower edges suggested that the integration region was larger at 16 Hz or above than at 8 Hz. The results suggest that the channels which mediate vernier hyperacuity are phase sensitive and attenuate frequencies higher than 8 Hz.
我们研究了对比度和时间频率对游标边缘对齐阈值的影响。边缘由相邻矩形在空间均匀亮度下的时间调制波形中180度的相位差来定义。在高对比度和高达8Hz的闪烁频率下，可以获得10角秒或更低的阈值。在此范围之上，阈值随着对比度降低和闪烁频率增加而迅速增加。对于归一化到闪烁或边缘检测阈值的对比度，在0 - 20Hz范围内，阈值也随着时间频率增加而增加。在不同时间频率下阈值与对比度的对数 - 对数图上进行线性回归表明，在8Hz或更低的时间频率下，阈值与对比度之间的关系可以用指数约为 -0.5的幂律很好地描述。在约8Hz时，斜率增加了一倍多，阈值升高。当上边缘和下边缘的相对相位（即对比度的瞬时符号）反转时，阈值也会增加，并且在所有时间频率下都观察到这种效应。作为上下边缘之间间隙大小的函数的阈值测量表明，在16Hz或更高频率下的积分区域比在8Hz时更大。结果表明，介导游标超敏锐度的通道对相位敏感，并衰减高于8Hz的频率。
