Fig 2. I_f in a simulated voltage clamp protocol using various current formulations.

I_f starting at -40 mV with hyperpolarizing steps to -50 - -100 mV (in 10 mV increments) for 5 s, followed by a step back to -40 mV for another 5 s. Calculations have been performed using the “blank” cellular model of [5], i.e. membrane capacitance, g_f, and both internal and external ionic concentrations from [5] were used for all I_f variants. Top: I_f from [5] (Paci2018, left) and [9] (Severi2012, right); bottom: I_f from [11] (Fabbri2017, left) and [10] (Koivumäki2018, right).