The code provided models an ionic current, specifically an Ohmic potassium (K) current, which is a common feature in computational models of neuronal activity. This model is implemented based on the principles discussed in Rubin and Cleland (2006) in the Journal of Neurophysiology and is formulated for use within the NEURON simulation environment, a widely used tool for simulating neuronal dynamics. ### Biological Basis 1. **Ion Channel Modeling**: - The code simulates the behavior of potassium ion channels. Potassium channels are crucial in setting the membrane potential and shaping the action potentials in neurons. - The suffix `kO` indicates that this is a model of an Ohmic potassium current, which operates under the assumption of a linear relationship between the current and the membrane potential. 2. **Ohmic Current**: - An Ohmic current implies that the current through the channel follows Ohm's Law, which states that the current (`i`) is directly proportional to the voltage difference across the membrane. - Here, the potassium current (`iO`) is defined by the conductance (`gkbar`) and the driving force, which is the difference between the membrane potential (`v`) and the equilibrium potential (`eO`) for potassium ions. 3. **Equilibrium Potential**: - The equilibrium potential (`eO`) is set to -90 mV, typical for potassium ions, and represents the membrane potential at which there is no net flow of potassium ions across the membrane. 4. **Conductance**: - `gkbar` represents the maximum conductance of the potassium channels. In this model, it is a parameter that can be adjusted to reflect different physiological or experimental conditions. 5. **Neuronal Application**: - Potassium currents play a significant role in repolarizing the neuron during action potentials, contributing to the afterhyperpolarization phase and influencing firing patterns and neuronal excitability. This model provides a simplified representation of potassium ion channel dynamics, assuming a constant conductance for a given potential. By modeling the potassium current in this way, it can be used to investigate how changes in potassium channels or variations in their properties might influence neuronal behavior in a computational setting.