Impact of dendritic size and dendritic topology on burst firing in pyramidal cells.
Impact of dendritic size and dendritic topology on burst firing in pyramidal cells.
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DOI：
10.1371/journal.pcbi.1000781
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发表时间：
2010-05-13
影响因子：
4.3
通讯作者：
van Ooyen A
中科院分区：
文献类型：
--
作者：
van Elburg RA;van Ooyen A
神经元表现出广泛的内在放电模式。神经元信号和突触可塑性的一种特别相关的模式是爆发式放电，即产生具有短间歇放电间隔的动作电位簇。除了离子通道组成，树枝状形态似乎是调节放电模式的一个重要因素。然而，其潜在的机制还不是很清楚，形态对爆发式发射的影响仍然不够清楚。树突状细胞的形态不是固定的，但在许多病理条件下会发生显着变化。利用新皮质锥体细胞的计算模型，我们表明，不仅顶端树突的总长度，而且其分支模式的拓扑结构显著地影响爆发间和爆发内的棘波间隔，甚至决定细胞是否表现出爆发放电。我们发现，只有一个范围的树枝大小支持爆发发射，并且这个范围受到树枝拓扑的调制。无论是缩小或扩大树突，还是在不改变树突总长度的情况下改变其拓扑结构，都可以将细胞的放电模式从爆发式转变为紧张式。有趣的是，结果在很大程度上与细胞是由胞体电流注入还是由分布在树突树上的突触刺激无关。通过一种名为平均电渗路径长度的新方法，我们证明了树突形态对爆发式放电的影响归因于树突大小和树突拓扑结构的影响，而不是对躯体输入电导的影响，而是对树突树的平均空间范围和树突膜电位的时空动力学的影响。我们的结果表明，锥体细胞形态的大小或拓扑结构的变化，如阿尔茨海默病、智力低下、癫痫和慢性应激，可以改变神经元的爆发式放电，从而最终影响信息处理和认知。神经元具有高度分枝的延伸，称为树突，形成特有的树状结构。这些树突状分支的形态在许多病理条件下都会发生显著的变化。然而，树突形态的改变如何影响神经元的活动仍然知之甚少。利用锥体细胞的计算模型，研究了树突大小和分枝结构对爆发式放电的影响。爆发式放电是两个或多个动作电位的紧密相继产生，是神经元活动的一种形式，与神经元信号转导和突触可塑性密切相关。我们发现，只有一个范围的树枝树大小支持爆发，并且这个范围是由树的分枝结构调制的。我们发现，由于树突膜电位的时空动态变化，缩短和延长树突树，甚至只是改变树上分支连接的模式，可以将细胞的激发模式从爆发转变为紧张性激发。我们的结果表明，锥体细胞形态的改变可能通过它们对爆发式放电的影响，最终影响认知。
Neurons display a wide range of intrinsic firing patterns. A particularly relevant pattern for neuronal signaling and synaptic plasticity is burst firing, the generation of clusters of action potentials with short interspike intervals. Besides ion-channel composition, dendritic morphology appears to be an important factor modulating firing pattern. However, the underlying mechanisms are poorly understood, and the impact of morphology on burst firing remains insufficiently known. Dendritic morphology is not fixed but can undergo significant changes in many pathological conditions. Using computational models of neocortical pyramidal cells, we here show that not only the total length of the apical dendrite but also the topological structure of its branching pattern markedly influences inter- and intraburst spike intervals and even determines whether or not a cell exhibits burst firing. We found that there is only a range of dendritic sizes that supports burst firing, and that this range is modulated by dendritic topology. Either reducing or enlarging the dendritic tree, or merely modifying its topological structure without changing total dendritic length, can transform a cell's firing pattern from bursting to tonic firing. Interestingly, the results are largely independent of whether the cells are stimulated by current injection at the soma or by synapses distributed over the dendritic tree. By means of a novel measure called mean electrotonic path length, we show that the influence of dendritic morphology on burst firing is attributable to the effect both dendritic size and dendritic topology have, not on somatic input conductance, but on the average spatial extent of the dendritic tree and the spatiotemporal dynamics of the dendritic membrane potential. Our results suggest that alterations in size or topology of pyramidal cell morphology, such as observed in Alzheimer's disease, mental retardation, epilepsy, and chronic stress, could change neuronal burst firing and thus ultimately affect information processing and cognition. Neurons possess highly branched extensions, called dendrites, which form characteristic tree-like structures. The morphology of these dendritic arborizations can undergo significant changes in many pathological conditions. It is still poorly known, however, how alterations in dendritic morphology affect neuronal activity. Using computational models of pyramidal cells, we study the influence of dendritic tree size and branching structure on burst firing. Burst firing is the generation of two or more action potentials in close succession, a form of neuronal activity that is critically involved in neuronal signaling and synaptic plasticity. We found that there is only a range of dendritic tree sizes that supports burst firing, and that this range is modulated by the branching structure of the tree. We show that shortening as well as lengthening the dendritic tree, or even just modifying the pattern in which the branches in the tree are connected, can shift the cell's firing pattern from bursting to tonic firing, as a consequence of changes in the spatiotemporal dynamics of the dendritic membrane potential. Our results suggest that alterations in pyramidal cell morphology could, via their effect on burst firing, ultimately affect cognition.
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4.1
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