Characteristics of Clustering and Switching in Verbal Fluency in Mild Cognitive Impairment and Dementia of Alzheimer’s Type

Objectives: The purpose of this study was to compare the performance on a verbal fluency task, clustering and switching characteristics, and proportion by error type between healthy elderly, Mild Cognitive Impairment (MCI) and Dementia of Alzheimer’s Type (DAT) group. Methods: Thirty healthy elderly, 30 MCI and 29 DAT individuals were asked to produce words in the category of ‘supermarket items’ for semantic fluency and ‘ㄱ’, ‘ㅇ’, and ‘ㅅ’ Korean letter categories for phonemic fluency with one minute allotted per category. Results: First, the number of correct responses in the verbal fluency task was significantly different between groups, with post hoc analyses showing significant differences between the healthy elderly and DAT groups and between the MCI and DAT groups. Second, the mean cluster size was not significant between groups in the semantic fluency task. However, it was significant between the healthy elderly and DAT groups, and between MCI and DAT groups in the phonemic fluency task. Third, the number of switches was significant between the healthy elderly and DAT elderly. Finally, the three groups had the highest proportion of perseverative errors in the semantic fluency task and the highest proportion of other errors in the phonemic fluency task. Conclusion: This study has clinical significance in that it examined the number of correct responses and characteristics of clustering and switching on verbal fluency tasks in the healthy elderly, MCI and DAT groups.