Modifying the spatial distribution of Na_V subtypes in the AIS while keeping the total conductance constant.

(A) The spatial separation of Na_V subtypes in the AIS is varied using the parameter “x” with κ = 0.5. The top plot is a model setup with a separated distribution [15, 20] of Na_Vs in the AIS. The high threshold Na_V1.2 (indicated in blue) are concentrated close to the soma, and the low threshold Na_V1.6 (indicated in orange) are kept distal to the soma. Moving from top to bottom, both Na_V subtypes are distributed ever more evenly along the AIS. We chose the parameter name “x” to vary the spatial separation of the AIS Na_V distributions, because the separated distribution is x-shaped. Setting x = 1 in our simulations gives the separated distribution, and x = 0 gives the “flat” distribution wherein both Na_V subtypes are uniformly mixed. (B) Variation of the crossover location (κ) of Na_Vs in the AIS with x = 0.5. We have lengthened the AIS to in this graphic for visual clarity.