Dementia and Parkinson's disease.

Recent research into the dementia of Parkinson's disease has exposed a complex area in which it has not always been possible to match clinical and pathological observations. Certain neuropsychological deficits result from a disruption of basal ganglia and frontal lobe interactions. These are unrelated to a global dementia, the prevalence of which exceeds twice that in the normal population. The associated pathological lesions comprise cortical pathology, either Alzheimer's disease or Lewy bodies, in combination with moderate degeneration of the subcortical, cholinergic, basal nucleus of Meynert.