Analysis of verbal fluency in amnestic and non-amnestic mild cognitive impairment

Background: Mild Cognitive Impairment (MCI) is defined as significant memory impairment that lies somewhere on the spectrum between normal, healthy aging and dementia. Tests of verbal fluency are simple and efficient tools that have shown to be sensitive enough to discriminate between healthy aging and early cognitive decline. The purpose of this study was to investigate letter and category verbal fluency abilities in two subtypes of MCI: amnestic and non-amnestic, and two domains of amnestic MCI: single and multiple. Methods: Participants were 25 persons with single domain amnestic MCI, 49 with multiple domain amnestic MCI, 16 with non-amnestic MCI, and 90 cognitively healthy older adults. Participants were asked to generate as many words as possible belonging to a category “animal” or beginning with a specific letter “f”. Verbal fluency performance on the letter and category fluency subtests were analyzed across 30-second intervals and according to the clustering and switching scoring paradigm developed by Troyer et al., 1998. Results: Single domain amnestic MCI was found to be the least impaired of our MCI groups, performing comparably to the control group on each dependent measure across both fluency tasks. The Multiple domain amnestic MCI group showed equal impairment in word and switch generation on both fluency tasks while the non-amnestic MCI group performed more poorly, in terms of word and switch production, on the letter fluency task compared to the category fluency task. Conclusions: Our findings demonstrate that verbal fluency performance is sensitive enough to discriminate between MCI groups. Results from the study also lend evidence to the understanding of the functional brain areas that are compromised at the MCI stage of impairment.