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Abstract

Pyramidal cells of the CA1 area in the hippocampus are one of the most studied neurons nowadays due to their role in memory formation or spatial navigation. CA1 pyramidal cells possess an apical dendrite which receives excitatory synaptic input mainly from CA3 axons.

To better understand apical synaptic input to these neurons, a new recording technique is proposed to measure excitatory synaptic input applied onto neurons. First, the theoretical derivations are presented. Then, the technique is applied to measure CA1 pyramidal cells and finally a computational model studies in depth the influence of the distance between synaptic input and recording on the estimation. The conclusion is that the method cannot improve current experimental techniques.

In addition, in some cases the axon of a neuron stems out of a dendrite rather than out of the soma. This particular morphology favors synaptic inputs onto this dendrite to generate action potentials. A computational model is applied to characterize the propagation of synapses from dendrites to the axon in a neuron with this feature. The model shows that electronic propagation is responsible of this favorable action potential generation.

Finally, extracellular stimulation of the axons of CA1 pyramidal cells generates ectopic action potentials with a bimodal distribution of time to arrive to the soma. The computational model suggests that this bimodal distribution is due to two different sites of action potential initiation, namely the axon initial segment and the first node of ranvier.