AN INTRACELLULAR ANALYSIS OF GENICULO-CORTICAL CONNECTIVITY IN AREA 17 OF THE CAT
AN INTRACELLULAR ANALYSIS OF GENICULO-CORTICAL CONNECTIVITY IN AREA 17 OF THE CAT
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DOI：
10.1113/jphysiol.1983.sp014846
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发表时间：
1983-01-01
影响因子：
5.5
通讯作者：
LINDSTROM, S
中科院分区：
文献类型：
--
作者：
FERSTER, D;LINDSTROM, S
在猫视觉皮层第17区神经元上记录了电刺激外侧束状核传入信号引起的兴奋性和抑制性突触后电位潜伏期（e.p.s.p和i.p.s.p）。应用外推程序补偿传入轴突的传导时间后，潜伏期直方图形成3个不同的峰。这些电位被解释为是由单突触、二突触和三突触通路介导的。利用外侧膝状核（l.g.n）诱发的细胞外场电位的特征性层流差异以及lg.n和上丘神经元的反序激活来确定所记录神经元的层流位置。研究发现，在同一层内，所有细胞都与lg.n中的中继细胞保持着相似的连接。第3、4、上5和6层的细胞受到膝状传入信号的单突触兴奋，而第2和下5层的细胞仅通过其他皮质神经元接受间接兴奋。第3层细胞除了受到l.g.n的直接刺激外，还具有明显的解突触性e.p.s.p.。后期，在许多第5层和第6层细胞中可见到三突触性e.p.s.p.成分。连接的有序层状排列导致识别的皮质-膝状神经元受到膝状传入事件的单突触兴奋，皮质-丘状神经元受到二突触和三突触兴奋。第2层和第3层皮质神经元接受双或单加失联兴奋，取决于层间位置。在所有刺穿细胞中，在刺激膝丘-皮层通路后都诱发了突触后抑制电位。除少数2层细胞外，这种抑制作用是通过前馈型失联通路介导的。在同一细胞中，单突触性e.p.s.p.和双突触性i.p.s.p.的传导时间呈良好的正相关，表明皮质神经元受到同一类型膝状传入事件的兴奋和抑制。刺激电极不仅激活了膝皮层传入神经，而且从皮层外轴突反方向激活了皮层传出神经元。这些神经元具有皮质内侧枝，必须注意区分由此产生的电位和那些由膝状传入事件的正交激活介导的电位。从第2层和第3层到第5层，从第5层到第6层，从第6层到第4层，获得了兴奋性连接的证据。未观察到典型的复发性抑制。许多神经元的感受野特性在穿透前被检查。第4层和第6层的细胞是简单的，它们都受到lg.n的单突触刺激。第2层、第3层和第5层的细胞以及第6层的少数非突出细胞具有复杂的感受野。这些细胞的连通性随层流位置的不同而不同。第6层和上5层的复杂细胞受到lg.n的直接刺激，第3层的复杂细胞受到直接外加间接刺激，第2层和下5层的复杂细胞受到间接刺激，讨论了这些结果对皮层感受野构建的意义。
The latencies of excitatory and inhibitory post-synaptic potentials (e.p.s.p. and i.p.s.p.) evoked by electrical stimulation of afferents from the lateral geniculate nucleus were recorded in neurons of area 17 of the cat visual cortex. After application of an extrapolation procedure to compensate for the conduction time of the afferent axons, a histogram of latencies formed 3 distinct peaks. Potentials in each of these were interpreted as being mediated by mono-, di- and trisynaptic pathways. Characteristic laminar differences in the extracellular field potentials evoked from the lateral geniculate nucleus (l.g.n.) and in the antidromic activation of neurons from the l.g.n. and superior colliculus were used to determine the laminar position of recorded neurons. It was found that within a given layer, all cells maintained similar connections with relay cells in the l.g.n. Cells in layers 3, 4, upper 5 and 6 were monosynaptically excited by geniculate afferents, while cells in layers 2 and lower 5 received only indirect excitation via other cortical neurons. Layer 3 cells were unique in receiving a prominent disynaptic e.p.s.p. in addition to the direct excitation from the l.g.n. Late, trisynaptic e.p.s.p. components were seen in many layer 5 and 6 cells. The orderly laminar arrangement of the connections had the consequence that identified cortico-geniculate neurons were monosynaptically excited and corticocollicular neurons di- and trisynaptically excited by geniculate afferents. Corticocortical neurons in layers 2 and 3 received di- or mono-plus disynaptic excitation, depending on laminar position. Post-synaptic inhibitory potentials were evoked in all impaled cells, following stimulation of the geniculo-cortical pathways. Except for a few layer 2 cells, this inhibition was mediated through disynaptic pathways of the feed-forward type. There was a good positive correlation between conduction times for monosynaptic e.p.s.p. and disynaptic i.p.s.p. in the same cells, suggesting that cortical neurons receive excitation and inhibition from the same type of geniculate afferents. The stimulating electrodes activated not only geniculo-cortical afferents, but antidromically activated cortical efferent neurons from their extracortical axons. These neurons possess intracortical collaterals, and care must be taken to distinguish the resulting potentials from those mediated by orthodromic activation of geniculate afferents. Evidence was obtained for excitatory connections from layers 2 and 3 to layer 5, from layer 5 to layer 6 and from layer 6 to layer 4. Typical recurrent inhibition was not observed. The receptive field properties of many neurons were examined before penetration. Simple cells were found in layers 4 and 6 and they all received prominent monosynaptic excitation from the l.g.n. Cells in layers 2, 3 and 5, as well as a few non-projecting cells in layer 6, had complex receptive fields. The connectivity of these cells varied with laminar position. Complex cells in layers 6 and upper 5 received direct excitation, those in 3 direct plus indirect excitation and those in 2 and lower 5 only indirect excitation from the l.g.n. The significance of these results for the construction of cortical receptive fields is discussed.