A study of the action potential initiation site along the axosomatodendritic axis of neurons using compartmental models

Abstract

The classic view establishing a unique site for AP initiation at the axon initial segment is not longer accepted. Different subrogions of the neuron morphology may initiate and conduct APs, widening enormously the computational capabilities of individual neurons. The experimental investigation of non-linear dendritic properties is subject to error because of they are very sensitive to recording conditions. We used an experimentallyfitted compartmental model to examine the factors modulating the AP initiation site of hippocampal pyramidal neurons. Our results indicate that synchronous spatially clustered inputs initiate dendritic APs more effectively than equivalent disperse inputs. The average electrical distance from the dendritic input to the axon trigger zone also determines the initiation site, but it may be strongly modulated by a number of factors, such as the relative excitability of the two trigger zones. The computational meaning of the shifts in the AP initiation locus is discussed. © Springer-Verlag Berlin Heidelberg 2003.