The Hindmarsh–Rose model of neuronal activity is aimed to study the spiking -bursting behavior of the membrane potential observed in experiments made with a single neuron. The relevant variable is the membrane potential, x (t), which is written in dimensionless units. There are two more variables, y (t) and z (t), which take into account the transport of ions across the membrane through the ion channels. The transport of sodium and potassium ions is made through fast ion channels and its rate is measured by y (t), which is called the spiking variable. z (t) corresponds to an adaptation current, which is incremented at every spike, leading to a decrease in the firing rate. Then, the Hindmarsh–Rose model has the mathematical form of a system of three nonlinear ordinary differential equations on the dimensionless dynamical variables x (t), y (t), and z (t). They read: