不同视刺激的视诱发电位的波形特征和规律

Waveform Features and Rule of Cortical Potentials Evoked by Different Visual Stimuli

不同视刺激的人脑视诱发电位（ＶＥＰ）有着不同的波形特征和规律。光闪ＶＥＰ随刺激亮度增高，峰时缩短，波幅增大；频闪刺激时反应出现多峰，随频率增高波幅逐渐下降，同步的ＶＥＰ的空间频率极限接近刺激频率３０次／Ｓ。棋盘格ＶＥＰ随空间频率由低增高，波幅迅速增大。至某一空间频率时，再增高空间频率，波幅又迅速减小，对某一空间频率反应最大。对比度ＶＥＰ波幅开始随对比度增大而迅速增大，峰时开始则随对比度增大而迅速缩短。增至某一对比度时，波幅上升明显减慢，峰时缩短减少，对比度增至１００％时，波幅达到最大值，峰时变化甚小；红绿蓝三基色ＶＥＰ，波形上有明显差别，波形较上述几种波形复杂。红色刺激的ＶＥＰ峰时最短，蓝色刺激的ＶＥＰ峰时最长。两负波波幅比值随波长变化呈红－绿色或红－蓝色拮抗。

Different characters and rules were found in the evoked potentials(VEP) by different visual stimuii.It’s peak time decreased with the increase of flash lu-minance. Several peak appeared and the amplitude decreased with the increase of stimu-lating flicker frequency. Amplitude increased rapidly with the increase of spatial frequen-cy,until a critical level,then one decreases rapidly. Amplitude increased rapidly and peaktime shortened rapidly with increase of contrast. Increase in amplitude and shortening inpeak time slowed down gradually when contrast went beyond a critical value. In the caseof 100% contrast , the amplitude became maximum , and peak time varied verv little. VEP waveform of the response evoked by different colour stimuli were significantly dif-ferent and more complex than the above. The peak time evoked by red stimuli was theshortest , and that by blue stimuli was the longest. Antagonism appeared in the ratio ofN1/N2 for red-green or red-blue stimuli.