Switching and its Impact on Perseveration in a Verbal Fluency Task: a Study in Persons With Alzheimer's Clinical Syndrome.

Abstract

Objective: The relationship between perseveration and switching in semantic verbal fluency tasks and the possible role of self-generated interference one must overcome before switching back to a previously visited subcategory has not been explored.

Participants & method: We studied the performance on semantic verbal fluency in 60 cognitively unimpaired subjects, 30 patients with amnestic mild cognitive impairment (aMCI) and 30 patients with Alzheimer's Clinical Syndrome-dementia (ACS-Dementia). Our primary analysis focused on the association of switching and switchback with the first perseverative error.

Results: Perseveration was significantly associated with switchback in all three groups (χ2 = 24.88, p < .001). Within-cluster perseverations were few. The number of switchbacks was the only significant variable to predict perseverative responses (p < .01). Moving from cognitively unimpaired to aMCI to ACS-Dementia, progressively fewer switches and switchbacks were needed to trigger perseveration. In over half of the perseverations after a switchback in the cognitively unimpaired and aMCI groups and in over a third in the ACS-Dementia group, the subjects had already activated a new word in the switched back subcategory.

Conclusion: Switching between subcategories and subsequent switchback play an important role in triggering perseverations in semantic verbal fluency tasks in the cognitively unimpaired as well as in aMCI and ACS-Dementia. Self-generated interference caused by repeated switching may overwhelm the working memory capacity enough to reactivate a previously suppressed response when revisiting an earlier subcategory. Our findings may facilitate a deeper understanding of the cognitive mechanisms underlying perseveration in semantic fluency tests.