Trends across volume are similar to trends across volume-to-surface-area ratio. Peak calcium levels, decay time constant, and synaptic weight updates for size variations given as volumes for filopodia-shaped spines (a–c), thin spines (d–f), mushroom spines (g–i), and mushroom spines with SpApp (j–l). Peak calcium is fitted with a line with a fixed zero intercept. *, **, and *** denote statistically significant values between the different sized spines. P values for each comparison are shown in Fig. S12.