Modeling the two firing modes of a regular spiking layer 5 neocortical pyramidal neuron

In vitro, the regular spiking layer 5 neocortical pyramidal neurons fire trains of single spikes in response to a somatically injected current pulse of sufficient amplitude and can respond with one or more bursts of action potentials to tonic apical dendritic stimulation. To investigate the mechanisms underlying this behavior, a complex model neuron was developed and tested. The results showed that the absence of the high voltage-activated (HVA) Ca²⁺ currents in the soma and proximal apical dendrites, the absence or the weak presence of these currents in the basal dendrites and a moderate presence in the proximal part of the apical trunk can account for the discharge patterns of the neurons under study.