Kovács G, Fischer-Szatmári L, Benedek G
Department of Physiology, Albert Szent-Györgyi Medical University, Szeged, Hungary.
Neurobiology (Bp). 1993;1(1):33-45.
Pattern reversal visually evoked potentials (PR-VEPs) were recorded in the anterior ectosylvian visual area (AEV) of the cat, and the dependence of the PR-VEPs on the spatial frequency (SF) and the mean luminance of the stimulation was studied. Six SFs between 0.025 and 1 cycles per degree (c/d) and four light density levels between 2 x 10(-2) and 117 cd/m2 (candela per square meter) were tested. The latency of the first positive component (P1) and the amplitude measured between P1 and the first negative (N1) component were analyzed. The dependence of the PR-VEP latencies on the SF displayed a significant relationship, with a minimum at around 0.05 c/d. This relationship was consistent at all luminance levels tested. The dependence of the amplitudes on the SF gave a "low-pass" tuning curve at every luminance level. The higher the luminance level, the steeper was the curve. The cut-off SF of these curves was at around 1 c/d under photopic conditions and around 0.6 c/d under scotopic conditions. The contrast dependence of the PR-VEP amplitudes exhibited saturation at 0.5, which was much higher than that of either the striate cortex or other extrastriate visual cortical areas, but similar to that of the superior colliculus. These results provide further evidence in support of the notion of a tecto-extrageniculo-extrastriate visual pathway functioning separately from the geniculo-striate mechanisms.
在猫的前外侧视区（AEV）记录了模式翻转视觉诱发电位（PR-VEPs），并研究了PR-VEPs对空间频率（SF）和刺激平均亮度的依赖性。测试了0.025至1周/度（c/d）之间的六个SF以及2×10⁻²至117坎德拉/平方米（cd/m²）之间的四个光密度水平。分析了第一个正向成分（P1）的潜伏期以及在P1和第一个负向（N1）成分之间测量的振幅。PR-VEP潜伏期对SF的依赖性显示出显著关系，在约0.05 c/d处有最小值。这种关系在所有测试的亮度水平下都是一致的。振幅对SF的依赖性在每个亮度水平下都给出了一条“低通”调谐曲线。亮度水平越高，曲线越陡峭。在明视条件下，这些曲线的截止SF约为1 c/d，在暗视条件下约为0.6 c/d。PR-VEP振幅的对比度依赖性在0.5时表现出饱和，这比纹状皮层或其他纹外视觉皮层区域的饱和度高得多，但与上丘的饱和度相似。这些结果为与膝状体-纹状机制分开运作的顶盖-外侧膝状体-纹外视觉通路这一概念提供了进一步的证据支持。
