Hoshino Noriaki, Matsumoto Nobuyoshi
Kyushu Institute of Technology, Faculty of Computer Science and Systems Engineering, Department of Biophysical Engineering and Science, Iizuka, 820-8502, Fukuoka, Japan.
Brain Res. 2003 Mar 21;966(2):185-93. doi: 10.1016/s0006-8993(02)04153-7.
The directional sensitivity of tectal neurons of the frog was examined by means of in vivo whole cell recording technique. Three kinds of stimulus were applied; (1) diffuse light 'on-off', (2) moving dark spot and (3) light spot given at one dimensional grid points. The first stimulus revealed whether or not retinal 'on-off' (R3) or 'off' (R4) fibers contribute to the response. As reported earlier, the following patterns were found for both light 'on' and light 'off': EPSPs only, IPSPs only or a combination of EPSPs and IPSPs. Four directionally sensitive neurons and three non-directionally sensitive neurons were found using the second stimulus. Using the third stimulus, responses at up to 11 positions separated by 2 degrees or 4 degrees were recorded. By measuring the amplitudes of 'on' and 'off' responses at different times, spatio-temporal receptive fields were composed. Two types of directional sensitivity were found. The response of the first type was composed of exclusively excitatory potentials, but the second type was composed of a combination of excitatory and inhibitory potentials. The spatio-temporal receptive field of the second type showed spatially separated excitatory and inhibitory regions with constant latencies. Such simple spatio-temporal receptive field organization was not found for directional sensitive neurons of the cat visual cortex. The spatio-temporal receptive field organization of the second type of directionally sensitive neuron in the present study is in agreement with striated receptive field found in some of the T5 neurons classified by extracellular unit recording [Frog Neurobiology (1976) 297].
利用活体全细胞记录技术研究了青蛙顶盖神经元的方向敏感性。施加了三种刺激：(1) 漫射光的“开 - 关”；(2) 移动的暗点；(3) 在一维网格点处给予的光点。第一种刺激揭示了视网膜“开 - 关”（R3）或“关”（R4）纤维是否对反应有贡献。如先前报道，对于光“开”和光“关”都发现了以下模式：仅兴奋性突触后电位（EPSPs）、仅抑制性突触后电位（IPSPs）或EPSPs与IPSPs的组合。使用第二种刺激发现了四个方向敏感神经元和三个非方向敏感神经元。使用第三种刺激，记录了在相隔2度或4度的多达11个位置的反应。通过测量不同时间的“开”和“关”反应的幅度，构建了时空感受野。发现了两种方向敏感性。第一种类型的反应仅由兴奋性电位组成，但第二种类型由兴奋性和抑制性电位的组合组成。第二种类型的时空感受野显示出具有恒定潜伏期的空间分离的兴奋性和抑制性区域。在猫视觉皮层的方向敏感神经元中未发现这种简单的时空感受野组织。本研究中第二种类型的方向敏感神经元的时空感受野组织与通过细胞外单位记录分类的一些T5神经元中发现的条纹状感受野一致[《青蛙神经生物学》（1976年）297]。
