Isolated disturbances of motivation and action have recently been reported following focal (anoxic, toxic or ischemic) lesions of the basal ganglia. Their postulated mechanism is thought to involve bilateral dysfunction in a cortico-subcortical loop centered on the limbic part of the striato-pallidum. Such disturbances also occur as a consequence of more diffuse brain damage, such as in vascular or degenerative dementias. Clinically, patients show dramatic decrease in spontaneous acts, whereas the same acts are correctly performed on external demand (so-called "loss of auto activation"). Moreover, they also demonstrate a special "loss of interest, affect and elan vital" which is relevant to both diagnosis and physiopathologic issues. Finally, they very often report a unique feature of decrease or absence of spontaneous thoughts, which is reversible upon external stimulation as well. In this article, the various clinical features of this syndrome are reviewed, based on the relevant literature as well as the author's personal experience. A new rating scale is proposed in order to evaluate specifically disorders of motivation and action in brain-damaged patients.