Figure 7.

The model predicts and data confirm that AIS surface area is a more effective driver of firing rate than somatodendritic (SD) area. A1, A2, In the model (A1), firing rate decreases slightly with increased somatodendritic surface area, as tested within the physiologically observed range of somatodendritic surface areas. In the experimental data (A2), a negative trend in firing rate is observed as somatodendritic surface area increases, but it does not achieve significance. B1, B2, In the model (B1), firing rate increases with increasing AIS surface area. In the experimental data (B2), firing rate is positively correlated with AIS surface area. C1, C2, In the model (C1), firing rate increases as the AIS/somatodendritic surface area ratio is varied. In the experimental data (C2), there is a tight correlation between AIS/somatodendritic surface area ratio (see results). Spearman's correlation coefficient (r) is shown in A2, B2, and C2.