(A) ECIII and CA3 neurons are represented by single ECIII and CA3 nodes. Reduced model of a CA1 pyramidal neuron consists of four CA1 nodes electrically coupled together, representing the apical tuft, more-proximal apical dendrites (dends), soma, and basal dendrites. Shown are voltage responses of single, uncoupled ECIII, CA3, and CA1 neurons to 2-ms current injections of 200 pA, 200 pA, and 375 pA, respectively. The backpropagating action potential into the apical dendritic compartments of our CA1 pyramidal cell model shows that it has weakly excitable dendrites.
(B) ECIII and CA3 cells receive external current inputs during the simulations. An ECIII cell provides input to the distal dendritic compartment of a CA1 cell, and a CA3 cell innervates its proximal dendritic compartment. Synaptic potentials are modeled as alpha functions, and if the voltage in the presynaptic cell exceeds −30 mV, an input is given to the postsynaptic cell.