Many neurological disorders are accompanied by depression. Because the clinical presentations of mood symptoms in neurological patients are similar to those seen in primary affective illness, it has been argued that neurological depressions are appropriate and useful models in the study of the pathophysiology of mood disorders in general. A group of hypotheses based on evidence from descriptive, experimental, and theoretical studies have in fact been proposed suggesting involvement of specific neural pathways and a variety of neurotransmitters in depression associated with particular neurological syndromes. 1–13 Al-though a single unifying mechanism for these depressions has not yet been established, the presence of affective symptoms in specific neurological diseases provides a framework for examining the basic neural systems regulating mood and emotions.