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.
Highlights
Tests of word generation are commonly used in neuropsychological assessment
To clarify some of the remaining questions about the cerebellum and fluency, we investigated verbal fluency as part of a larger study of cognition in a group of patients with focal cerebellar injuries, carefully screened for any complicating co-morbidity and only tested in a late, stable epoch after injury
The right cerebellar lesion (RC) group had impaired verbal fluency in both tasks when compared to the LC group and controls for phonemic and to controls only for semantic
Summary
Tests of word generation are commonly used in neuropsychological assessment. There are two types of tasks. Lesions in a broad region of the left hemisphere and the right frontal lobe may impair verbal fluency, some due to direct damage to language systems or the auditory-verbal short term memory component of working memory, but others presumably due to damage to strategic or monitoring requirements. There is convergent support for the role of both the left prefrontal cortex and the right cerebellum for both forms of word generation tasks from neuroimaging activation studies in normal healthy individuals [5,10]. To clarify some of the remaining questions about the cerebellum and fluency, we investigated verbal fluency as part of a larger study of cognition in a group of patients with focal cerebellar injuries, carefully screened for any complicating co-morbidity and only tested in a late, stable epoch after injury
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