Memory deficits in advanced Parkinson's disease.

Apart from global dementia various isolated cognitive deficits have been described in Parkinson's disease (PD). We investigated 31 non-demented Parkinsonian patients in their late stages of disease and 50 control subjects with regard to verbal memory. Eleven patients suffered from an isolated verbal memory deficit as defined by two list learning tasks using the Buschke selective reminding procedure. The isolated memory impairment did not depend on depression but was associated with longer duration of PD. Twelve demented PD patients were comparable to PD patients with isolated memory impairment with regard to age at onset and duration of PD. We speculate that the isolated memory impairment in PD is associated with isolated neuronal loss in the nucleus basalis of Meynert, without cortical or limbic pathology of the Alzheimer's type.