Zemon V, Gutowski W, Horton T
Int J Neurosci. 1983 May;19(1-4):259-86. doi: 10.3109/00207458309148661.
Orientational anisotropy in the human visual system was investigated using electrophysiological and psychophysical techniques. Grating patterns of various orientations were presented and contrast detection thresholds were measured using a two alternative forced choice procedure. Using the same observers, visual evoked cortical potentials (VECPs) were elicited by identical gratings set at various contrasts ranging from subthreshold to high levels. Plots of contrast sensitivity versus grating orientation were derived using the amplitude of a negative wave of the VECP for low contrast data and the amplitude of a positive wave for moderate to high contrast data. These plots were compared with plots obtained during the psychophysical experiment. The results indicate that the low contrast VECP functions exhibit an orientational anisotropy that is qualitatively and quantitatively similar to that observed in the psychophysical data. The high contrast VECP functions, however, exhibit an orientational effect that is qualitatively similar but greater in magnitude than that found in the low contrast VECP or psychophysical experiments. These findings suggest that the amplitudes of VECPs elicited by low contrast stimuli are highly correlated with psychophysical detection performance, and that an additional physiological mechanism is reflected in the VECPs elicited by moderate to high contrast stimuli.
利用电生理和心理物理学技术研究了人类视觉系统中的方向各向异性。呈现了各种方向的光栅图案，并使用二选一强制选择程序测量了对比度检测阈值。使用相同的观察者，通过设置在从阈下到高水平的各种对比度下的相同光栅诱发视觉诱发电位（VECP）。对于低对比度数据，使用VECP负波的幅度，对于中等到高对比度数据，使用正波的幅度，得出对比度敏感性与光栅方向的关系图。将这些图与心理物理学实验中获得的图进行比较。结果表明，低对比度VECP功能表现出一种方向各向异性，在质量和数量上与心理物理学数据中观察到的相似。然而，高对比度VECP功能表现出一种方向效应，在质量上相似，但幅度比低对比度VECP或心理物理学实验中发现的更大。这些发现表明，低对比度刺激诱发的VECP幅度与心理物理学检测性能高度相关，并且在中等到高对比度刺激诱发的VECP中反映了一种额外的生理机制。
