A Comparison of Phonemic, Semantic, and Alternating Word Fluency in Parkinson's Disease

Archives of Clinical Neuropsychology, Vol. 14, No. 3, pp. 255–264, 1999 Copyright © 1999 National Academy of Neuropsychology Printed in the USA. All rights reserved 0887-6177/99 $–see front matter PII S0887-6177(98)00008-0 Ronald F. Zec Department of Psychiatry, Department of Neurology, Center for Alzheimer Disease and Related Disorders, Southern Illinois University School of Medicine Edward S. Landreth, Sally Fritz, Eugenia Grames, Ann Hasara, and Wade Fraizer Department of Psychology, University of Illinois at Springfield James Belman Alton Mental Health Center Stacy Wainman Department of Speech Pathology, Illinois State University Matthew McCool Department of Psychology, Illinois State University Carolyn O’Connell Human Development and Counseling, University of Illinois at Springfield Rosemary Harris Department of Psychiatry, Department of Neurology, Center for Alzheimer Disease and Related Disorders, Southern Illinois University School of Medicine Randall Robbs Statistics and Research Consulting, Southern Illinois University School of Medicine Rodger Elble Department of Neurology, Center for Alzheimer Disease and Related Disorders, Southern Illinois University School of Medicine Bala Manyam Department of Neurology, Southern Illinois University School of Medicine Address correspondence to: R. F. Zec, Center for Alzheimer Disease and Related Disorders, Southern Illinois University School of Medicine, Springfield, IL 62794-9230 255 A Comparison of Phonemic, Semantic, and Alternating Word Fluency in Parkinson’s Disease 256 R. F. Zec et al. There is a growing body of evidence suggesting that non-demented patients with Parkinson’s disease (PD) have difficulty in rapidly alternating mental set (e.g., Bowen, Hoehn, & Yahr, 1972; Bowen, Burns, Brady, & Yahr, 1976; Cools, Van Den Bercken, Horstink, Van Spaendonck, & Berger, 1984; Fimm, Bartl, Zimmermann, & Wallesch, 1994; Flowers & Robertson, 1985; Lees & Smith, 1983; McDonald, Brown, & Gorell, 1996; Sandson & Albert, 1987). This set-switching deficit is found on tasks that require the use of internal attentional control. For example, PD patients have been reported to be impaired on tasks that require the subject to generate words belonging to two different semantic categories in rapid alternation (Cooper, Sagar, Jordan, Harvey, & Sullivan, 1991; Gotham, Brown, & Marsden, 1988; Rothlind & Brandt, 1993). However, due to methodological limitations of these studies, it is unclear whether this impairment in Alternating Word Fluency (AWF) is primarily due to a deficit in generating words or whether the set-shifting requirement imposes an additional cognitive load. In addition, Gurd and Ward (1989) did not find a disproportionate deficit in AWF compared to single word fluency in PD patients, and concluded that “task switching” per se is not impaired in PD. Gotham et al. (1988) reported a disproportionate deficit in performance on an AWF task, compared with performance on a semantic word fluency (SWF) task. The PD group when off levodopa treatment generated 25% fewer words on the AWF task as compared with the healthy control subjects. However, there were no statistically significant differences between the groups on the AWF task when the PD group was on levodopa. The PD patients, whether on or off levodopa, did not differ significantly from controls on the SWF task. The authors interpreted their findings as indicating that PD patients off levodopa have deficient dopamine in the frontostriatal system, which may cause set shifting difficulty on the AWF task. A limitation of this study is that only a single AWF trial and a single SWF trial were employed. Two other studies found a deficit in AWF but without evidence for a disproportionate deficit compared to single word fluency tasks. Cooper et al. (1991) reported a deficit in AWF in a group of newly diagnosed, untreated PD patients, but in their study, the AWF deficit was not greater than the SWF deficit. Rothlind and Brandt (1993) employed an AWF task as part of a brief assessment battery that they developed and validated for the detection of frontal-subcortical dysfunction in non-demented PD and Huntington’s disease (HD) patients. The PD group and HD group generated approximately 32% fewer words on the AWF task than the control group, but it is unclear whether this AWF task performance was due to reduced verbal fluency, impaired set-shifting, or both, because a single word fluency comparison test was not included. Word fluency in 45 medicated non-demented Parkinson’s disease (PD) patients and 45 normal control subjects was studied with a Phonemic Word Fluency (PWF) task using the letters F, A, and S, a Semantic Word Fluency (SWF) task using the categories animals, boys’ names, and states, and an Alternating Word Fluency (AWF) task requiring the person to alternate between colors and occupations, animals and states, and words beginning with C and P. The number of words generated did not differ for trials with F, A, S, or states, but PD patients generated significantly fewer animal names and boys’ names. PD patients also generated significantly fewer words on each of the three AWF trials. The PD patients scored 21% lower than the normal control group on the total AWF score, but only 10% lower for the PWF and SWF scores. The greater impairment on the AWF task which requires the use of internal attentional control to rapidly shift mental set can be considered a type of executive functioning deficit. This is consistent with the growing literature suggesting frontal systems dysfunction in PD and with the view that dopaminergic treatment only incompletely restores functioning in the frontostriatal system. © 1999 National Academy of Neuropsychology. Published by Elsevier Science Ltd Alternating Word Fluency Deficit in PD 257 Gurd and Ward (1989) reported that there was no disproportionate deficit in performance on AWF compared with performance on either phonemic word fluency (PWF) or semantic word fluency (SWF) in a group of PD patients receiving dopaminergic medication compared to a group of healthy controls. The authors concluded that PD patients, including patients in the early stages, display markedly impaired verbal fluency performance on all types of generative naming tasks, but that there was no evidence for a disproportionate effect on alternating word fluency compared to single word fluency and thus “task switching” per se is not impaired in PD. Thus, unlike the Gotham et al. (1988) study, Gurd and Ward (1989) did not find a selective AWF deficit, but unlike Gurd and Ward, they did not test their subjects when “off” dopaminergic medications. Neither Gurd and Ward (1989) nor Gotham et al. (1988) found a disproportionate deficit in AWF compared to single word fluency when PD patients are “on” dopaminergic medications, but the two studies produced opposite findings with regard to single word fluency in PD patients when “on meds” (i.e., Gurd and Ward found (...truncated)