FIGURE 4.

(A) Compiled means ± SE of relative height and stiffness (elastic constant E/(1 − ν²)) between spines and dendrites, from regions of interest in force-volume data of spines with and without an axon present and spines stimulated with AMPA or glutamate. Significance of the stiffness increases from axon presence and stimulation were assessed by ANOVA, with p-values as indicated. (B) Dynamic tracking of elastic-storage and viscous-loss moduli (G′/k₀ and G″/k₀ as solid and open points, respectively) measured with 10-Hz indentation modulation. Both moduli increase within minutes of stimulation with AMPA (1 μM) and increased extracellular Ca²⁺. The dynamic response is reversed by introduction of the actin polymerization inhibitor latrunculin-A (Lat.A, 1 μM).