Geer I, Spafford M M
School of Optometry, University of Waterloo, Ontario, Canada.
Doc Ophthalmol. 1994;86(3):295-310. doi: 10.1007/BF01203553.
A small experimental, central scotoma significantly attenuates the human pattern visual evoked potential. The steady-state pattern visual evoked potential was recorded from seven visually normal adults who viewed a reversing checkerboard with 24' checks and a central scotoma that varied in size and shape. We found that square scotomas had to be at least 3 x 3 degrees to significantly (p < 0.05) attenuate the pattern visual evoked potential. Receptor density has been shown to be greater along the horizontal meridian than the vertical meridian. We hypothesized that this results in greater cortical representation of the horizontal meridian than the vertical meridian and, therefore, the pattern visual evoked potential might be significantly attenuated by a smaller rectangular scotoma oriented along the horizontal meridian than along the vertical meridian. One dimension of the rectangular scotoma was fixed at either 1 degree or 3 degrees, while the other dimension was varied from 1 degree to 8 degrees. The threshold scotoma size that significantly (p < 0.05) attenuated the pattern visual evoked potential was a horizontal scotoma subtending 1 x 4 degrees and a vertical scotoma subtending 5 x 1 degree (vertical x horizontal). Meridional differences in cortical representation were not apparent to the larger scotoma series in which the fixed dimension subtended 3 degrees (3 x 2 degrees and 2 x 3 degrees). Further analysis of the data revealed that the apparent meridional difference for the 1 degree scotoma series was a function of data variability. The determinant of the PVEP amplitude was scotoma area, not orientation. Monocular and binocular threshold scotoma sizes were the same, which could be due to the level of binocular summation demonstrated by our subjects.
一个小的实验性中心暗点会显著减弱人类的图形视觉诱发电位。从7名视力正常的成年人身上记录稳态图形视觉诱发电位，他们观看的是一个带有24'方格的反转棋盘以及一个大小和形状各异的中心暗点。我们发现方形暗点至少要有3×3度才能显著（p<0.05）减弱图形视觉诱发电位。已表明沿水平子午线的感受器密度大于垂直子午线。我们推测，这导致水平子午线在皮层的代表区比垂直子午线更大，因此，沿水平子午线方向的较小矩形暗点可能比沿垂直子午线方向的更小矩形暗点更能显著减弱图形视觉诱发电位。矩形暗点的一个维度固定为1度或3度，而另一个维度从1度变化到8度。能显著（p<0.05）减弱图形视觉诱发电位的阈值暗点大小为水平方向1×4度的暗点和垂直方向5×1度的暗点（垂直×水平）。对于固定维度为3度（3×2度和2×3度）的较大暗点系列，皮层代表区的子午线差异并不明显。对数据的进一步分析表明, 1度暗点系列中明显的子午线差异是数据变异性的一个函数。图形视觉诱发电位振幅的决定因素是暗点面积，而非方向。单眼和双眼的阈值暗点大小相同，这可能是由于我们的受试者所表现出的双眼总和水平。
