Clustering and switching strategies during verbal fluency performance differentiate Alzheimer's disease and healthy aging.

Clustering and switching strategies during phonemic and semantic verbal fluency tasks as defined by Troyer et al. (1997), Abwender et al. (2001), and Lanting et al. (2009) were compared using archival data to determine which scoring procedures best differentiate healthy older adults (n = 26) from individuals with early-stage Alzheimer's disease (AD, n = 26). Total word production showed the largest group difference, especially for semantic fluency. The AD group produced fewer switches when compared to the healthy control group, whereas the groups did not differ in cluster size. The AD group also accessed fewer novel semantic subcategories, presumably due to reduced access to semantic memory storage rather than lower processing speed. Clustering and switching scores on the phonemic task did not add information above total words produced, consistent with previous research indicating these variables are most informative in relation to semantic fluency.