Figure 12.

Dendritic membrane properties influence optimal AIS location relative to the soma. A, Diagram of a neuron with four dendrites having variable dendritic membrane properties and a 30 µm AIS positioned at variable distances from the soma (AIS Model C; myelinated axon). B, Voltage responses in the AIS during somatic current injections under baseline conditions (far left) and after manipulations of dendritic R_M and/or C_M, as indicated. Responses from three models are superimposed: those having the AIS beginning 0 (blue), 20 (green), or 50 µm (red) from the soma. C, Plots of normalized rheobase current vs AIS location for the four-dendrite models having modified dendritic R_M (top left), dendritic C_M (top right), parallel changes in both dendritic R_M and C_M (bottom left), or reciprocal changes in dendritic properties (bottom right). Dendritic C_M and/or R_M were multiplied by the indicated modification factors. C_M/R_M ratios in reciprocal manipulations of R_M and C_M are centered around baseline (C_M/R_M ratio = 1) values. Increasing dendritic C_M and/or dendritic conductance (lower dendritic R_M) enhanced excitability at more distal AIS locations. Shaded bars indicate the AIS locations for which traces are shown in B.