Verbal fluency deficits in Parkinson's disease: individual differences in underlying cognitive mechanisms

Although it is now well established that patients with idiopathic Parkinson's disease (PD) frequently have verbal fluency deficits [1,2], the issue of individual differences has yet to be addressed experimentally. Evidence presented here demonstrates that the underlying information processing causes of PD verbal fluency deficits may differ from person to person. These studies have been carried out on non-demented PD patients. The theoretical issues of case-series research and population homogeneity in cognitive neuropsychology are also discussed. (C) 2000 Elsevier Science Ltd. All rights reserved.