Mitzdorf U, Singer W
Exp Brain Res. 1978 Nov 15;33(3-4):371-94. doi: 10.1007/BF00235560.
The current source density (CSD) method in its one-dimensional approximation is used to analyze the field potentials in visual areas 18 and 17 of the cat, which were elicited by stimulating electrodes in the optic chiasm (OX), the optic radiation (OR) or in the respective cortical area itself. The CSD analysis reveals the basic pattern of excitatory postsynaptic activity. 1. In both visual areas the basic specific excitatory activity flows along three different intracortical pathways, all starting in layer IV: The first pathway relays activity from layer IV to supragranular pyramidal cells via strong, local connections to layer III and from there through long-distance connections to layer II. The second pathway conveys activity from layer IV to layer V, where it mainly contacts apical dendrites of layer VI pyramidal cells. This infragranular polysynaptic activity is not clearly resolvable into separate components, suggesting that it is conveyed by various groups of axons, among them long-distance horizontal connections. The third pathway has one synaptic relay within layer IV and then conveys activity to layer III. In addition, monosynaptic activity is revealed in layers VI and I. 2. In A 18 one coherent, fast-conducting group of afferents induces this basic activity pattern. In A 17 no such fast conducting input is resolvable; the supragranular activity is induced by a small group of afferents with intermediate conduction velocity, which terminate in the upper part of layer IV. The infragranular activity is induced by afferents with slower and widely scattered conduction velocities, which terminate in the lower part of layer IV. The layer VI input is very prominent in A 17 and also has a wide latency scatter. 3. The supragranular activity is more prominent in A 18 than in A 17 and the respective layers appear thicker, in accordance with anatomy. In A 17 the infragranular activity prevails and layers IV and VI appear very broad, again in accordance with anatomy. 4. Comparison of the CSDs with the original evoked potentials shows that the surface evoked potentials over A 18 reflect the three dipolar sink/source distributions of the coherent monosynaptic activity in layer IV and of the two prominent polysynaptic activities in layers III and II. The widely scattered activity in the lower part of layer IV in A 17 and all infragranular activities in both areas generate smaller, partly closed-field potentials; those are not discernible from the strong far-field potentials which originate from the supragranular activity and--especially in A 17--from farther distant events.
采用一维近似的电流源密度（CSD）方法，分析猫的视区18和视区17中的场电位，这些场电位是由刺激视交叉（OX）、视辐射（OR）或相应皮质区域本身的电极所诱发的。CSD分析揭示了兴奋性突触后活动的基本模式。1. 在两个视区中，基本的特异性兴奋性活动沿着三条不同的皮质内通路流动，所有通路均始于第IV层：第一条通路通过与第III层的强局部连接，将活动从第IV层中继到颗粒上层锥体细胞，并从那里通过长距离连接到第II层。第二条通路将活动从第IV层传递到第V层，在那里它主要与第VI层锥体细胞的顶树突接触。这种颗粒下多突触活动无法清晰地分解为单独的成分，这表明它是由各种轴突群传递的，其中包括长距离水平连接。第三条通路在第IV层内有一个突触中继，然后将活动传递到第III层。此外，在第VI层和第I层中还发现了单突触活动。2. 在视区18中，一组连贯的、传导速度快的传入纤维诱发了这种基本活动模式。在视区17中，无法分辨出这样快速传导的输入；颗粒上层活动是由一小群传导速度中等的传入纤维诱发的，这些传入纤维终止于第IV层上部。颗粒下活动是由传导速度较慢且广泛分散的传入纤维诱发的，这些传入纤维终止于第IV层下部。第VI层输入在视区17中非常突出，并且潜伏期散布也很广。3. 与解剖结构一致，颗粒上层活动在视区18中比在视区17中更突出，并且相应的层看起来更厚。在视区17中，颗粒下活动占主导，第IV层和第VI层看起来非常宽，同样与解剖结构一致。4. 将CSD与原始诱发电位进行比较表明，视区18上方的表面诱发电位反映了第IV层中连贯单突触活动以及第III层和第II层中两个突出的多突触活动的三个偶极汇/源分布。视区17中第IV层下部广泛分散的活动以及两个区域中的所有颗粒下活动产生较小的、部分封闭场电位；这些电位与源自颗粒上层活动以及——尤其是在视区17中——更远距离事件的强远场电位无法区分。
