Burr D C, Corsale B
Istituto di Neurofisiologia del CNR, Via S. Zeno 51, 56127, Pisa, Italy.
Vision Res. 2001 Apr;41(8):1039-48. doi: 10.1016/s0042-6989(01)00019-0.
We measured reaction times for detecting the onset of motion of sinusoidal gratings of 1 c/deg, modulated in either luminance or chromatic contrast, caused to move abruptly at speeds ranging from 0.25 to 10 deg/s (0.25-10 Hz). At any given luminance or chromatic contrast, RTs varied linearly with temporal periodicity (r2 congruent with 0.97), yielding a Weber fraction of period. The value of the Weber fraction varied inversely with contrast, differently for luminance and chromatic contrast. The results were well simulated with a simple model that accumulated change in contrast over time until a critical threshold had been reached. Two crucial aspects of the model are a second-stage temporal integration mechanism, capable of accumulating information for periods of up to 2 s, and contrast gain control, different for luminance than for chromatic stimuli. The contrast response for luminance shows very low semi-saturating contrasts and high gain, similar to LGN M-cells and cells in MT; that for colour shows high semi-saturating contrasts and low gain, similar to LGN P-cells. The results suggest that motion onset for luminance and chromatic gratings are detected by different mechanisms, probably by the magno- and parvo-cellular systems.
我们测量了检测1 c/deg正弦光栅运动起始的反应时间，这些光栅在亮度或颜色对比度上进行调制，并以0.25至10 deg/s（0.25 - 10 Hz）的速度突然移动。在任何给定的亮度或颜色对比度下，反应时间随时间周期呈线性变化（r2约为0.97），得出周期的韦伯分数。韦伯分数的值随对比度呈反比变化，亮度和颜色对比度的情况不同。用一个简单模型对结果进行了很好的模拟，该模型随着时间累积对比度变化，直到达到临界阈值。该模型的两个关键方面是二级时间积分机制，能够累积长达2秒的信息，以及对比度增益控制，亮度刺激和颜色刺激的情况不同。亮度的对比度响应显示出非常低的半饱和对比度和高增益，类似于外侧膝状体M细胞和MT中的细胞；颜色的对比度响应显示出高半饱和对比度和低增益，类似于外侧膝状体P细胞。结果表明，亮度和颜色光栅的运动起始是通过不同机制检测的，可能是通过大细胞和小细胞系统。
