Dendritic Size and Topology Influence Burst Firing in Pyramidal Cells
Neurons have highly branched dendrites that form characteristic tree-like structures. The morphology of these dendritic arborizations is not fixed and can undergo significant alterations in many pathological conditions. However, little is known about the impact of morphological changes on 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 show 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. 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. The influence of dendritic morphology on burst firing is attributable to the effect that dendritic size and branching pattern have on the average spatial extent of the dendritic tree and the spatiotemporal dynamics of the dendritic membrane potential. Our results suggest that alterations in pyramidal cell morphology, such as those observed in Alzheimer’s disease, mental retardation, epilepsy, and chronic stress, can change neuronal burst firing and thus ultimately affect information processing and cognition.