Bex Peter J, Langley Keith
Schepens Eye Research Institute, Harvard Medical School, Boston, MA 02114, USA.
J Vis. 2007 Sep 10;7(12):1.1-23. doi: 10.1167/7.12.1.
We examine how the perceived contrast of dynamic noise images depends upon temporal frequency (TF) and mean luminance. A novel stepwise suprathreshold matching paradigm shows that both threshold and suprathreshold contrast sensitivity functions may be described by an inverted-U shape as a function of TF. The shape and the peak TF of the tuning function vary with the conditions under which it is measured. Spatiotemporal vision is weakly band-pass at low luminance levels (0.8 cd/m(2)) but becomes more strongly band-pass at high luminances (40-400 cd/m(2)). The peak temporal frequencies of the band-pass functions increase with the mean luminance and contrast of the test signals. As a function of increasing image contrast, our results demonstrate that the visual system broadens the spatiotemporal bandwidth of its signal detection mechanisms, especially at high mean luminances. Our results are shown to be consistent with an adaptable signal transmission system in which early luminance-dependent gain control mechanisms, in combination with on-line estimates of contrast via the autocorrelation function lead to an adaptive enhancement of spatiotemporal vision at high temporal frequencies.
我们研究了动态噪声图像的感知对比度如何取决于时间频率（TF）和平均亮度。一种新颖的逐步超阈值匹配范式表明，阈值和超阈值对比度敏感度函数均可描述为TF的倒U形函数。调谐函数的形状和峰值TF会随测量条件而变化。在低亮度水平（0.8 cd/m²）下，时空视觉呈弱带通特性，但在高亮度（40 - 400 cd/m²）时会变得更强的带通特性。带通函数的峰值时间频率随测试信号的平均亮度和对比度增加而增加。作为图像对比度增加的函数，我们的结果表明视觉系统拓宽了其信号检测机制的时空带宽，尤其是在高平均亮度时。我们的结果表明与一种适应性信号传输系统一致，在该系统中，早期的亮度依赖增益控制机制与通过自相关函数对对比度的在线估计相结合，导致在高时间频率下时空视觉的自适应增强。
