Fig. 9.

(Ca, s) phase plane for the adaptation model. The structures (curves of fixed points, FP, and left knees, LK) defined when drive is increased are labeled with the Λ symbol; σ, σ̂ denote the s values at which FP and LK intersect with baseline and increased drive, respectively. The duration of the silent phase is dependent on how Ċa and Ca_LK change with g_app, as well as on |∂Ca_LK/∂s|. (a) A small |∂Ca_LK/∂s| promotes a long silent phase, with relatively high sensitivity to changes in Ċa (dashed and dotted curves), seen as large changes in the s-value at which the trajectory reaches $\widehat{\mathit{\text{LK}}}$ with changes in Ċa. (b) A large |∂Ca_LK/∂s| promotes a short silent phase, with relatively low sensitivity to changes in Ċa (dashed and dotted curves), seen as small changes in the s-value at which the trajectory reaches $\widehat{\mathit{\text{LK}}}$ with changes in Ċa