To the Editor.
—In their article on "Pathologic Correlates of Dementia in Parkinson's Disease" Chui et al1 present clinicopathologic data suggesting that dementia in this disorder may be associated with severe neuronal loss in subcortical nuclei without significant corticohippocampal Alzheimer's pathology, while similar subcortical changes were seen in Alzheimer's disease. These data are of interest in view of the still controversial problem of the morphological basis for the intellectual impairment in Parkinson's disease and its relation to Alzheimer's disease.2 However, some recent data on subcortical lesions in both Parkinson's and Alzheimer's disease should be added, since they may contribute to the understanding of "subcortical dementia" and related disorders.First, while the well-established findings of significant neuronal loss in the dopaminergic (substantia nigra), noradrenergic (locus ceruleus), and cholinergic (nucleus basalis of Meynert) systems in both Parkinson's and Alzheimer's disease are confirmed in the above-mentioned study, no reference is given to recent