Subcortical dementia occurs both in disorders affecting the basal ganglia (for example, Parkinson's disease, Huntington's disease, and progressive supranuclear palsy) and in a variety of subcortical vascular, infectious, inflammatory, neoplastic, and traumatic conditions. The principal features of subcortical dementia include bradyphrenia, impairment of executive function, recall abnormalities, visuospatial disturbances, depression, and apathy. The syndrome contrasts with dementia of the Alzheimer type in which cortical involvement produces aphasia, combined recall and recognition deficits, and indifference. Electrophysiologic, biochemical, and metabolic studies support a distinction between subcortical and cortical dementias.