Anzai A, Bearse M A, Freeman R D, Cai D
School of Optometry, University of California at Berkeley.
Vis Neurosci. 1995 Jan-Feb;12(1):77-93. doi: 10.1017/s0952523800007331.
Many psychophysical studies of various visual tasks show that performance is generally better for binocular than for monocular observation. To investigate the physiological basis of this binocular advantage, we have recorded, under monocular and binocular stimulation, contrast response functions for single cells in the striate cortex of anesthetized and paralyzed cats. We applied receiver operating characteristic analysis to our data to obtain monocular and binocular neurometric functions for each cell. A contrast threshold and a slope were extracted from each neurometric function and were compared for monocular and binocular stimulation. We found that contrast thresholds and slopes varied from cell to cell but, in general, binocular contrast thresholds were lower, and binocular slopes were steeper, than their monocular counterparts. The binocular advantage ratio, the ratio of monocular to binocular thresholds for individual cells, was, on average, slightly higher than the typical ratios reported in human psychophysics. No single rule appeared to account for the various degrees of binocular summation seen in individual cells. We also found that the proportion of cells likely to contribute to contrast detection increased with stimulus contrast. Less contrast was required under binocular than under monocular stimulation to obtain the same proportion of cells that contribute to contrast detection. Based on these results, we suggest that behavioral contrast detection is carried out by a small proportion of cells that are relatively sensitive to near-threshold contrasts. Contrast sensitivity functions (CSFs) for the cell population, estimated from this hypothesis, agree well with behavioral data in both the shape of the CSF and the ratio of binocular to monocular sensitivities. We conclude that binocular summation in behavioral contrast detection may be attributed to the binocular superiority in contrast sensitivity of a small proportion of cells which are responsible for threshold contrast detection.
许多针对各种视觉任务的心理物理学研究表明，双眼观察的表现通常优于单眼观察。为了探究这种双眼优势的生理基础，我们在单眼和双眼刺激条件下，记录了麻醉和瘫痪猫的纹状皮层中单个细胞的对比度响应函数。我们对数据应用了接受者操作特征分析，以获得每个细胞的单眼和双眼神经测量函数。从每个神经测量函数中提取对比度阈值和斜率，并对单眼和双眼刺激进行比较。我们发现，对比度阈值和斜率因细胞而异，但总体而言，双眼对比度阈值较低，双眼斜率比单眼对应值更陡。双眼优势比，即单个细胞的单眼阈值与双眼阈值之比，平均略高于人类心理物理学中报道的典型比值。似乎没有单一规则可以解释单个细胞中观察到的不同程度的双眼总和现象。我们还发现，可能参与对比度检测的细胞比例随着刺激对比度的增加而增加。与单眼刺激相比，双眼刺激时获得相同比例的参与对比度检测的细胞所需的对比度更低。基于这些结果，我们认为行为对比度检测是由一小部分对接近阈值的对比度相对敏感的细胞进行的。根据这一假设估计的细胞群体的对比度敏感度函数（CSF），在CSF的形状以及双眼与单眼敏感度的比值方面都与行为数据非常吻合。我们得出结论，行为对比度检测中的双眼总和可能归因于一小部分负责阈值对比度检测的细胞在对比度敏感度方面的双眼优势。
