Figure 8. Effect of the electrode length, membrane excitability and tissue conductivity on the safety factor.

Safety factor profiles obtained with the safety factor formulation SF_m2 for suprathreshold (thick lines) and subthreshold (thin lines) amplitudes close to the threshold are represented. A: 4 mm (dashed dotted lines), 8 mm (solid lines) and 12 mm (dashed lines) electrode size, the inset shows the SF_VB profiles for comparison; B: control (solid lines), 50% reduction of the maximum sodium conductance (g_Na) (dashed lines) and 75% reduction of tissue conductivity (σ) (dashed dotted lines), the inset shows the SF_VB profiles for comparison; and C: control (solid lines), 50% reduction of the maximum sodium conductance (g_Na) (dashed lines) and 75% reduction of tissue conductivity (dashed dotted lines), 70% reduction of g_Na (short dashed lines) and 87.5% reduction of tissue conductivity (dotted lines). The shaded profile indicates the critical safety factor obtained with our formulation (SF_m2).