Memory and learning in early Parkinson's disease: evidence for a "frontal lobe syndrome".

Fifteen untreated patients in the earliest stages of Parkinson's disease were compared to fifteen age- and intellectually matched control subjects on a number of memory tasks assessing short- and long-term recall of both meaningful and unrelated material, semantic relations in the organization of memory, priming, and source forgetting, and the ability to form new stimulus-response associations under conditions of maximal task interference. While patients demonstrated considerable evidence of preserved function, impaired performance on a subgroup of tasks was consistent with selective frontostriatal system involvement. These findings are discussed with reference to the underlying pathological processes in Parkinson's disease.