Figure 5: Incremental increase of ionic concentration and associated neck resistance decrease during high-frequency synaptic stimulation.

a) Relative variations of ion concentration in the spine head (R= 300 nm) and associated neck resistance for a 20 Hz synaptic stimulation (geometrical neck resistances (i.e. at concentration c₀): 500 MΩ (blue) and 100 MΩ (red)). The kinetics of the synaptic conductance is $g^{+}(t)=\frac{g_{0}exp\left(-\frac{t}{{\tau }_2}\right)}{1+exp\left(-\frac{t-\mu }{{\tau }_1}\right)},$ with maximal conductance$g_0=5nS,$ and dynamical paramaters $\mu =0.52ms,{\tau }_1=0.11and{\tau }_2=3.95ms)$ b) Relative variations for 50 Hz synaptic stimulation.