The caudate forms the medial part of the striatum and has clear involvement with both cognitive and motor functions. Damage to this structure has been reported to produce a ‘schizophrenia-like’ state, and so has been the subject of some investigation. As with the adjacent putamen, the caudate receives dopaminergic input from the nigrostriatal tract, with recent imaging studies suggesting a pronounced effect of anti-psychotic medication on the size of this structure.