This work highlights new and functionally profound cross talk between the dendritic tree and the axon initial segment, providing new understanding of neurons as sophisticated nonlinear input/output devices.Įncoding rapid changes in synaptic inputs via axonal spikes is a key function of neurons and of the networks they form ( Ilin et al., 2013).
In the latter case, phase locking reached close to 1 KHz in in vivo-like conditions. The cutoff frequency of spikes phase locking to modulated inputs increased from 100 to 200 Hz in pyramidal cells of young rats to 400–600 Hz in human cells. This “dendritic size effect” was explored both analytically as well as numerically, in simplified and detailed models of 3D reconstructed layer 2/3 cortical pyramidal cells of rats and humans. Hence, our findings imply that neurons with larger dendritic arbors have improved encoding capabilities. AP onset rapidness is key in determining the capability of the axonal spikes to encode (phase lock to) rapid changes in synaptic inputs.
We show that the size of the dendritic arbors (its impedance load) strongly modulates the shape of the action potential (AP) onset at the axon initial segment it is accelerated in neurons with larger dendritic surface area.
This study highlights a new and powerful direct impact of the dendritic tree (the input region of neurons) on the encoding capability of the axon (the output region).
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