Newton Jessica R, Eskew Rhea T
Psychology Department, Northeastern University, 125 Nightingale Hall, Boston, USA.
Vis Neurosci. 2003 Sep-Oct;20(5):511-21. doi: 10.1017/s0952523803205058.
The peripheral visual field is marked by a deterioration in color sensitivity, sometimes attributed to the random wiring of midget bipolar cells to cone photoreceptors in the peripheral retina (Mullen, 1991; Mullen & Kingdom, 1996). Using psychophysical methods, we explored differences in the sensitivity of peripheral color mechanisms with detection and discrimination of 2-deg spots at 18-deg eccentricity, and find evidence for a postreceptoral locus for the observed loss in sensitivity. As shown before, observers' sensitivity to green was lower than to red in the periphery, although the magnitude of this effect differed across observers. These results suggest that the asymmetry in peripheral sensitivity occurs at a postreceptoral site, possibly a cortical one. In addition, noise masking was used to determine the cone inputs to the peripheral color mechanisms. The masked detection contours indicate that the red and green mechanisms in the periphery respond to the linear difference of approximately equally weighted L- and M-cone contrasts, just as they do in the fovea. Thus, if the midget retinal ganglion system is responsible for red/green color perception in the fovea, it is likely to be responsible at 18-deg eccentricity as well.
周边视野的特点是颜色敏感度下降，这有时归因于侏儒双极细胞与周边视网膜中视锥光感受器的随机连接（马伦，1991年；马伦和金德姆，1996年）。我们采用心理物理学方法，通过检测和辨别18°偏心率下的2°光斑，探究周边颜色机制敏感度的差异，并发现了感受器后位点导致观察到的敏感度损失的证据。如前所示，观察者在周边对绿色的敏感度低于对红色的敏感度，尽管这种效应的程度在不同观察者之间有所不同。这些结果表明，周边敏感度的不对称发生在感受器后位点，可能是皮质位点。此外，使用噪声掩蔽来确定周边颜色机制的视锥输入。掩蔽检测轮廓表明，周边的红色和绿色机制对大致等权重的L-和M-视锥对比度的线性差异做出反应，就像它们在中央凹中一样。因此，如果侏儒视网膜神经节系统负责中央凹中的红/绿颜色感知，那么它很可能在18°偏心率时也起作用。
