Affiliations: Division of Neurosurgery, St. Michael's Hospital,
Toronto, Canada | Keenan Research Centre of the Li Ka Shing Knowledge
Institute at St. Michael's Hospital, Toronto, Canada | Faculty of Medicine, Department of Surgery, Division
of Neurosurgery, University of Toronto, Toronto, Canada | Rotman Research Institute at Baycrest, Toronto,
Canada | Harvard Medical School and Beth Israel Deaconess
Medical Centre (Neurology), Boston, USA | Faculty of Medicine (Neurology, Rehabilitation
Sciences) and Psychology, University of Toronto, Toronto, Canada
Note: [] Corresponding author: Tom A. Schweizer, Ph.D., St. Michael's
Hospital, Division of Neurosurgery, 30 Bond Street, Toronto, ON, M5B 1W8,
Canada. Tel.: +1 416 864 5504; Fax: +1 416 864 5017; E-mail: [email protected]
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.
