The cerebellum is involved in motor coordination and the control of movement timing, as is demonstrated by loss of these functions with cerebellar diseases. Within the cerebellar circuits, the neurons of the deep cerebellar nuclei are key elements because, firstly, they are the main target of the cerebellar cortex, secondly, they receive copies of all cerebellar afferent information, and thirdly, they are the sole output of the cerebellum to its target structures. Despite the key position of these neurons, the microcircuit organization and cellular mechanisms determining their output is poorly understood. We investigate first, how intrinsic and synaptic mechanisms determine and control cerebellar nuclei neurons firing frequency and timing. Second, how plasticity of these mechanisms may contribute to adaptation under physiological as well as recover under pathological conditions. For this purpose we use in vitro electrophysiological recordings from wild type and transgenic animals combined with immuno-histochemistry.