Clustering and switching processes in semantic verbal fluency in the course of Alzheimer's disease subjects: Results from the PAQUID longitudinal study

Abstract

Reduced semantic fluency performances have been reported in the preclinical phase of Alzheimer's disease (AD). To investigate the cognitive processes underlying this early deficit, this study analyzed the verbal production of pre-demented subjects for the animals category with the qualitative parameters related to clustering (i.e. the ability to generate words belonging to semantic subcategories of animals) and switching (i.e. the ability to shift from one subcategory to another) proposed by Troyer.This qualitative analysis was applied to the PAQUID cohort, a 17-year longitudinal population-based study. The performances on the animal verbal fluency task of 51 incident cases of possible and probable AD were analyzed at the onset of dementia, 2 years and 5 years before dementia onset. Each case was matched for age, sex and education to two control subjects leading to a sample of 153 subjects. The mean cluster size and the raw number of switches were compared in the two samples. The results revealed a significantly lower switching index in the future AD subjects than in the elderly controls including 5 years before dementia incidence. A significant decline in this parameter was evidenced all along the prodromal phase until the clinical diagnosis of dementia. In contrast, the mean cluster size could not discriminate the two groups. Therefore the results support the hypothesis that impaired shifting abilities -rather than semantic memory storage degradation-could explain the early decline in semantic fluency performance occurring in the predementia phase of AD.

Verbal fluency in children with ADHD: Strategy using and temporal properties

“…Qualitative analysis of verbal fluency tasks was effective in predicting Alzheimer's Disease (AD) onset (Raoux et al, 2008). Less switching occurred in the future AD subjects than in the elderly controls during five years before dementia incidence.…”

“…Less switching occurred in the future AD subjects than in the elderly controls during five years before dementia incidence. In various psychiatric populations, like patients with depression, Huntington Disease, Parkinson's Disease, HIVassociated dementia, deficits in fluency have been related to a reduced number of switches (Fossati, Bastard Guillaume, Ergis, & Allilaire, 2003;Raoux, et al, 2008). Impaired shifting abilities could explain the decline in semantic fluency performance occurring in EF related syndromes (Raoux, et al, 2008).…”

“…In various psychiatric populations, like patients with depression, Huntington Disease, Parkinson's Disease, HIVassociated dementia, deficits in fluency have been related to a reduced number of switches (Fossati, Bastard Guillaume, Ergis, & Allilaire, 2003;Raoux, et al, 2008). Impaired shifting abilities could explain the decline in semantic fluency performance occurring in EF related syndromes (Raoux, et al, 2008). Analysis of switching and clustering showed fewer switches and smaller word clusters on phonemic and verbal fluency tasks in adult ADHD (Tucha, et al, 2005).…”

Cognitive correlates of cerebrospinal fluid biomarkers for Alzheimer’s disease

“…Indeed, in the non-AD dementia group, individuals with DLB (n=7) had the lowest B-SIT scores (DLB: mean 4.71, SD=2.98). B-SIT scores were also low in individuals with VaD (n=5, mean 6.00, SD=2.12) and FTD (n=14, mean: 5.51, SD=2.27), which is consistent with previous evidence suggesting impairment in odour identification in these disorders [39][40][41]. Yet, in these groups CSF tau concentrations are often not as high as in AD-type dementia [42].…”

“…Others found that abnormal amyloid was associated with greater decline on the 'Preclinical Alzheimer Cognitive Composite (PACC), which is a compound score that includes tests for episodic verbal memory, attention, and global cognitive functioning [39,40]. An early decline in the verbal fluency has been reported in individuals in predementia phase of AD [41]. We did find an association between CSF tau but not aβ42 on decline in the fluency.…”