A silicon implementation of the thalamic low threshold calcium current

A silicon model of the thalamic low threshold calcium current is presented. The channel current (IT) is the product of an activation and inactivation current, normalized by their sum. The individual currents are modeled by a simple current-mirror integrator circuit. A modified differential pair controls the threshold of activation while a leak transistor added to the inactivation mirror controls the rate of inactivation and deinactivation. The dynamics of IT are the result of the interaction between the fast activation and slow inactivation currents. By adjusting the base level of the activation current, we can realize a hyperpolarization activated cation current (Ih), responsible for rhythmic bursting in thalamic cells. By attaching the circuit to a constant leak integrate-and-fire neuron, we demonstrate in silicon both burst and tonic firing modes.