Differences between healthy adults and mild cognitive impairment patients in Category Fluency performance: A scoring method based on words’ Serial Recall Order and item‐level features

Abstract

AbstractBackgroundSemantic Memory (SM) alterations occur very early in preclinical AD. Category Fluency (CF) is the most widely‐used measure of free SM recall but is not effective at detecting subtle SM changes. Its score based on word‐count, in fact, is also influenced by other abilities such as processing speed and executive functioning.We thus designed an alternative, item‐level scoring method less susceptible to these intervenient variables. This quantifies “how difficult” each CF word is based on 9 semantic features. Additionally, the Serial Recall Order (SRO) is established. This is an ordinal variable that tags the position of each word within the recalled list. Participant‐specific correlations are then calculated between SRO and each semantic feature. These capture the tendency of each participant to recall increasingly difficult words.We previously showed that, in healthy adults, these correlational indices are associated with neurocognitive mechanisms of semantic processing and control, but are statistically independent of processing speed and executive functioning (https://doi.org/10.3389/fnagi.2021.678588; https://doi.org/10.3389/fpsyg.2021.777838).This study tests whether these indices differ between normal adults and patients with mild cognitive impairment (MCI) at risk of progressing to AD.MethodCF performance from 60 MCI patients and 60 matched controls was scored following the above methodology. ANCOVAs were run to test the effect of diagnosis on z‐converted correlational indices, controlling for age, educational attainment, and number of CF entries at the basis of the correlations.ResultOf the nine indices, ‘SRO‐dominance’ was the only one differing between diagnoses. This correlation was ≈‐0.204 in controls and ≈‐0.362 in patients. Words 1‐8 were of similar dominance between groups. A difference was found instead for Words 9‐12.Conclusion‘Dominance’ is the ‘degree of control/power’ conveyed by a word. While the general tendency of CF performance is that of recalling words that are increasingly dominant, this trend is significantly more pronounced in MCI. This suggests a different use of semantic‐control resources between groups when the target category is explored in more depth. Although preliminary, these findings indicate that the SRO of CF words can help profile SM in patients with suspected AD. More work is needed, however, to study diagnostic statuses informed by biomarkers.