Figure 6.

Determining the calcium spike threshold using voltage slope. (A) Distal membrane potential excursion due to a calcium spike triggered by a δ pulse synaptic input. Black dashed line denotes the determined threshold value (see text). (B) As in (A), but for an alpha synaptic conductance with a time constant τ_e = 5 ms. (C) Membrane potential V₀ at which the calcium potential slope $\left|\stackrel{.}{V}\right|$ is minimal as a function of τ_e. (D) Threshold for δ input. The intersection of V^d (red) against m ∈ [0, 1] (numerically obtained from Equation 5) and the inverse function of m_∞(V_d) ∈ [0, 1] (blue) against m (obtained by numerically inverting m_∞(V_d), derived from Equation 3) denotes the theoretical threshold for calcium spikes triggered by δ pulse synaptic inputs.