Field potential studies in vivo have shown that many subcortical structures, such as the inferior olivary nucleus, the thalamic nuclei and the lateral habenular nucleus, generate behaviorally relevant rhythms. In each region, intracellular analysis in brain slices has revealed that activation of a transient, low-threshold calcium current plays a pivotal role in rhythmogenesis. The membrane potential of each individual neuron may oscillate rhythmically as a result of interplay between this current and other inward and outward voltage and calcium-dependent currents. Synchronization of this oscillatory single-cell activity, through mutual interaction and/or appropriately timed afferent drive, results in generation of stereotyped population rhythms.