Fig 7. The roles of extracellular ions in CSD initiation: Representative time traces.

When Na_V1.1 carries a FHM-3 mutation, modeled by p_Na,P = 15%, we tested the effect of keeping either extracellular potassium or sodium constant using unrealistically high diffusion rates. We depolarized the neurons at rest with constant excitatory conductances g_D,i = g_D,e = 0.3 mS · cm⁻² for 30 s. A: Voltage traces for the default parameters. B: Voltage traces when ε = 0.1 ms⁻¹ to simulate a strong buffering of extracellular potassium. C: Voltage traces when there is a strong buffering of extracellular sodium. To implement it, we introduced the diffusion term I_diff,Na = ε_Na([Na⁺]_o − Na_bath) in the equation for extracellular sodium, with ε_Na = 0.1 ms⁻¹ and Na_bath equal to the steady-state extracellular sodium in the absence of external input. D: [K⁺]_o traces in the cases described in A-C. E: [Na⁺]_o traces in the cases described in A-C.