Abstract
Dendritic Ca2+ spike endows cortical pyramidal cell with powerful ability of synaptic integration, which is critical for neuronal computation. Here we propose a two-compartment conductance-based model to investigate how the Ca2+ activity of apical dendrite participates in the action potential (AP) initiation to affect the firing properties of pyramidal neurons. We have shown that the apical input with sufficient intensity triggers a dendritic Ca2+ spike, which significantly boosts dendritic inputs as it propagates to soma. Such event instantaneously shifts the limit cycle attractor of the neuron and results in a burst of APs, which makes its firing rate reach a plateau steady-state level. Delivering current to two chambers simultaneously increases the level of neuronal excitability and decreases the threshold of input-output relation. Here the back-propagating APs facilitate the initiation of dendritic Ca2+ spike and evoke BAC firing. These findings indicate that the proposed model is capable of reproducing in vitro experimental observations. By determining spike initiating dynamics, we have provided a fundamental link between dendritic Ca2+ spike and output APs, which could contribute to mechanically interpreting how dendritic Ca2+ activity participates in the simple computations of pyramidal neuron.
Highlights
Pyramidal neurons are common cell types found in the cerebral cortex and hippocampus of mammalian brain[1,2,3]
For simple global integration mode, input signals directly contribute to action potential (AP) output by triggering excitatory postsynaptic potentials (EPSPs) that spread to the AP initiation zone
The synaptic input directly activates the Ca2+ channel in dendrites and triggers dendritic spikes[7,14,15,16,17,20], which propagates forward to the axon where the global integration occurs[18,19]. Such integration lies at the heart of neural computation, which is tightly related to coincidence detection[1,16,21,22], orientation tuning[22], binding of synaptic signals from brain areas[23], School of Electrical and Information Engineering, Tianjin University, Tianjin 300072, China
Summary
Pyramidal neurons are common cell types found in the cerebral cortex and hippocampus of mammalian brain[1,2,3]. The additional inward current associated with Ca2+ spike provides a strong local depolarization in dendritic membrane, which can enhance the somatic/axonal AP outputs It can significantly increase the gain of input-output relation of pyramidal neuron, which triggers a burst of APs in the soma/axon and switches the firing mode of the cell to bursting[23,26,30,31,32]. It is still not well understood how dendritic Ca2+ spike participates in AP initiation to influence the somatic/axonal output. It is still largely unknown that how dendritic Ca2+ spike affects the AP initiation of individual pyramidal cells
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