Figure 2. Chronology of events underlying the thalamic alpha. A, The interburst interval determines the 10-Hz rhythm underlying the thalamic alpha. Membrane voltage (green) of a single HTC neuron as it goes through bursts of activity. C, D, Activity of relevant ion channels between the bursts for the duration of a 100-ms time window. F, G, Activity of the same channels during the 10-ms burst of the cell. B, Slowly increasing membrane voltage (green) due to the increase in IH conductance (blue, B) during repolarization of the membrane potential by the potassium current. The total current (black) increases with IH. The bursting activity is initiated by activation of ITHT current (red, E, F) and terminated by repolarization due to the potassium current. C, The hyperpolarization-activated current IH (blue) increases slowly during membrane repolarization leading to eventual activation of the ITHT (red). D, Gating variables of the IH (rH, blue) and ITHT (m2h, red) currents. The high-threshold calcium current gets activated around the ∼90-ms mark. E, The increase in ITHT activates the fast sodium channels and triggers a series of APs. Membrane potential (green) and total ionic current in the immediate 10 ms after the activation of ITHT. This burst of APs is initiated by IH and ITHT in that order (left panel). F, The high-threshold calcium current (red) provides a depolarizing impetus that sustains a burst of APs. The IH (blue) current becomes hyperpolarizing above −40-mV membrane voltage but does not contribute much in this phase due to low conductance values compared with the high-threshold calcium. G, The slow decay of the gating variables of the IH (blue) as the membrane potential rises above the activation voltage. The gating variables of ITHT (red) slowly deactivate at high voltages during APs.