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Behavioural Neurology
Volume 23 (2010), Issue 1-2, Pages 31-37
http://dx.doi.org/10.3233/BEN-2010-0269

Lateralized Cerebellar Contributions to Word Generation: A Phonemic and Semantic Fluency Study

Tom A. Schweizer,1,2,3 Michael P. Alexander,4,5 B. A. Susan Gillingham,4 Michael Cusimano,1,2,3 and Donald T. Stuss4,6

1Division of Neurosurgery, St. Michael's Hospital, Toronto, Canada
2Keenan Research Centre of the Li Ka Shing Knowledge Institute at St. Michael’s Hospital, Toronto, Canada
3Faculty of Medicine, Department of Surgery, Division of Neurosurgery, University of Toronto, Toronto, Canada
4Rotman Research Institute at Baycrest, Toronto, Canada
5Harvard Medical School and Beth Israel Deaconess Medical Centre (Neurology), Boston, USA
6Faculty of Medicine (Neurology Rehabilitation Sciences) and Psychology, University of Toronto, Toronto, Canada

Received 12 August 2010; Accepted 12 August 2010

Copyright © 2010 Hindawi Publishing Corporation and the authors. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

Impairment on verbal fluency tasks has been one of the more consistently reported neuropsychological findings after cerebellar lesions, but it has not been uniformly observed and the possible underlying cognitive basis has not been investigated. We tested twenty-two patients with chronic, unilateral cerebellar lesions (12 Left, 10 Right) and thirty controls on phonemic and semantic fluency tasks. We measured total words produced, words produced in the initial 15 seconds, errors and strategy switches. In the phonemic fluency task, the right cerebellar lesion (RC) group produced significantly fewer words compared to the left cerebellar lesion (LC) group and healthy controls, particularly over the first 15 seconds of the task with no increase in errors and significantly fewer switches over the entire task. In the semantic fluency task there was only a modest decrease in total words in the RC group compared to controls. RC lesions impair fluency with many of the same performance characteristics as left prefrontal lesions. This supports the hypotheses of a prefrontal-lateral cerebellar system for modulation of attention/executive or strategy demanding tasks.