Dec 1, 1995

A model of spike initiation in neocortical pyramidal neurons

Z F MainenT J Sejnowski


Neocortical pyramidal cells possess voltage-dependent dendritic sodium channels that promote propagation of action potentials into the dendritic tree but paradoxically may fail to originate dendritic spikes. A biophysical model was constructed to reconcile these observations with known anatomical and physiological properties. When dendritic and somatic sodium channel densities compatible with electrophysiological measurements were combined with much higher densities in the axon initial segment then, regardless of the site of stimulation, spikes initiated at the initial segment and subsequently invaded the dendrites. The lower initial segment threshold arose from high current density and electrical isolation from the soma. Failure of dendritic channels to initiate spikes was due to inactivation and source-load considerations, which were more favorable for conduction of back-propagated spikes.

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  • Citations225

Mentioned in this Paper

Initial Segment of Axon
Action Potentials
Transcription Initiation
Dendritic Tree
Pyramidal Cells

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