Verbal fluency declines after pallidotomy: An interaction between task and lesion laterality

Verbal fluency declines are commonly reported after pallidotomy in patients with Parkinson disease. However, it is not clear whether there is an interaction between side of surgery and task format (lexical vs. semantic) or whether error rates (perseverations, intrusions, rule violations) increase after surgery. This study examined verbal fluency before and approximately 4 months after unilateral pallidotomy. The left and right pallidotomy groups were matched on key demographic, cognitive, and disease variables. Pallidotomy resulted in a decline in lexical but not semantic verbal fluency, and this decline was most evident in the left-sided surgery group. Error rates (perseverations, intrusions, and rule violations) were not affected by pallidotomy. Findings support the role of left frontal-basal ganglionic circuits in word retrieval processes and/or lexical search and access.