背景光对图形视网膜电图空间调谐特性的影响

本工作应用背景光压抑闪光视网膜电图(FERG),考察对图形视网膜电图(PERG)的空间调谐特性的影响,并与无背景光时的结果进行比较。背景光使全屏幕闪光诱发的FERG基本压抑。在这种条件下,同屏幕的图形刺激所诱发的PERG的振幅显示一定的低空间频率衰减(LSFA)。FFT分析表明,当时间频率为3.91Hz时,PERG的二次谐波呈现十分明显的LS-FA,与无背景光时的结果吻合得很好;当时间频率为7.81Hz时,也表现出LSFA,而无背景光时则缺如。这些结果表明,无背景光时记录的PERG振幅在低空间频率区偏高确实是由于混杂有亮度特异性成分—FERG。但是,PERG振幅所显示的LSFA仍不如二次谐波那么明显,这可能是因为FERG中存在的非线性成分未为背景光所完全压抑,仍然混杂在低频区的PERG反应中。

EFFECTS OF BACKGROUND LIGHTS ON SPATIAL TUNING CHARACTERISTICS OF PATTERN ELECTRORETINOGRAMS

In the present study, spatial tuning characteristics of the pattern electrore-tinogram (PERG) were examined by using background lights to suppress flashelectroretinogram (FERG), and then compared with data obtained without back-ground lights. It was found that the amplitude of PERG responses showed aclearer low spatial frequency (<0.23 cpd) attenuation (LSFA) in the presenceof a background light for suppressing, to a large extent, the FERG response toflashing the whole screen with the same luminance. The second harmonic ofthe PERG, as revealed by fast fourier transformation technique, showed asignificant LSFA at 3.91 Hz in the presence of the background light, which is ingood agreement with the data obtained in the absence of background lights. Fur-thermore, the second harmonic clearly decreased at lower spatial frequencies(<0.23cpd) even at 7.81 Hz, while no decrease in the second harmonic was found withoutbackground lights. These results indicated that higher amplitudes of the PERGat lower spatial frequencies in the absence of background lights may indeed beattributed to an additional luminance-specific component -- FERG. However,LSFA of the PERG amplitude was not so significant as the second harmonic. Thismay be partly due to nonlinear components of the FERG that can not be suppressedby background lights and keep interfering with the PERG at lower spatial freguencies.