Properties of Piriform Cortex Pyramidal Cell Dendrites: Implications for Olfactory Circuit Design
Properties of Piriform Cortex Pyramidal Cell Dendrites: Implications for Olfactory Circuit Design
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DOI：
10.1523/jneurosci.1124-09.2009
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发表时间：
2009-10-07
影响因子：
5.3
通讯作者：
Larkum, Matthew E.
中科院分区：
文献类型：
--
作者：
Bathellier, Brice;Margrie, Troy W.;Larkum, Matthew E.
与新皮质不同，梨状皮质的感觉输入在解剖学上是在第1层分隔的，这使其非常适合研究对感觉信息处理至关重要的突触输入的树突整合。在此，我们使用沿胞体 - 顶端树突轴的双膜片钳记录技术，研究了锥体细胞中嗅球输入的树突整合。我们发现，这些树突相对紧凑，对于到达远端树突区域的突触输入，体细胞电流损失最大为50%。远端树突能够产生小而快速的局部电位发放，但它们对胞体影响很小，表明它们的活性较弱。与新皮质相反，我们没有发现树突Ca2+或NMDA电位发放的证据，尽管这些树突积极支持动作电位的反向传播以及伴随的Ca2+离子内流。基于实验和模拟，我们认为，无论树突位置如何，嗅球输入具有几乎相同的效力，并且在远端顶端树突（第Ia层）上广泛分布，从而将亚线性求和效应降至最低。这表明这些细胞进行的任何刺激特征提取都将在胞体发生，并且是基于嗅球输入的近乎线性总和，而不是基于树突树上明确设计的功能相关突触簇。
Unlike the neocortex, sensory input to the piriform cortex is anatomically segregated in layer 1, making it ideal for studying the dendritic integration of synaptic inputs pivotal for sensory information processing. Here we investigated dendritic integration of olfactory bulb inputs in pyramidal cells using dual patch-clamp recordings along the soma-apical dendritic axis. We found that these dendrites are relatively compact with 50% maximal somatic current loss for synaptic inputs arriving at distal dendritic regions. Distal dendrites could generate small and fast local spikes, but they had little impact on the soma, indicating that they are only weakly active. In contrast to the neocortex, we found no evidence for dendritic Ca2+ or NMDA spikes though these dendrites actively supported action potential backpropagation with concomitant entry of Ca2+ ions. Based on experiments and simulations we suggest that regardless of dendritic location, olfactory bulb inputs have nearly uniform potency and are distributed diffusely over the distal apical tree (layer Ia), thereby minimizing sublinear summation effects. This indicates that any stimulus feature extraction performed by these cells will occur at the soma and is based on the nearly linear sum of olfactory bulb inputs, rather than on explicitly designed clusters of functionally related synapses in the dendritic tree.