The basal ganglia are a collection of interconnected subcortical nuclei which have been implicated inmotor, cognitive and limbic functions. The subthalamic nucleus is the sole excitatory structure within the basal ganglia. Given its central position influencingmany basal ganglia nuclei, it is likely to play an important role in the processing that is performed by the basal ganglia. In this thesis a theoretical analysis of the subthalamic nucleus is presented. In order to explore the multiple facets of processing that may be occurring, models that are designed to capture aspects of the subthalamic nucleus at different levels are developed. These include anatomical, network processing and single neuron multi–compartmental models. Through the integration of the results obtained from these models a new and coherent view of the processing of the subthalamic nucleus is presented. It is predicted that the subthalamic nucleus be considered as a massively connected excitatory networ...