![]() Received: DecemAccepted: ApPublished: May 13, 2010Ĭopyright: © 2010 van Elburg, van Ooyen. Graham, Université Paris Descartes, Centre National de la Recherche Scientifique, France Our results suggest that alterations in pyramidal cell morphology could, via their effect on burst firing, ultimately affect cognition.Ĭitation: van Elburg RAJ, van Ooyen A (2010) Impact of Dendritic Size and Dendritic Topology on Burst Firing in Pyramidal Cells. 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. 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. 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. Using computational models of pyramidal cells, we study the influence of dendritic tree size and branching structure on burst firing. It is still poorly known, however, how alterations in dendritic morphology affect neuronal activity. The morphology of these dendritic arborizations can undergo significant changes in many pathological conditions. Neurons possess highly branched extensions, called dendrites, which form characteristic tree-like structures. 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. 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. 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. 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. We found that there is only a range of dendritic sizes that supports burst firing, and that this range is modulated by dendritic topology. 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. Dendritic morphology is not fixed but can undergo significant changes in many pathological conditions. However, the underlying mechanisms are poorly understood, and the impact of morphology on burst firing remains insufficiently known. Besides ion-channel composition, dendritic morphology appears to be an important factor modulating firing pattern. A particularly relevant pattern for neuronal signaling and synaptic plasticity is burst firing, the generation of clusters of action potentials with short interspike intervals. Neurons display a wide range of intrinsic firing patterns.
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