Exploring Verbal Fluency Strategies among Individuals with Normal Cognition, Amnestic and Non-Amnestic Mild Cognitive Impairment, and Alzheimer's Disease

Background and Objectives: The present study explored the utilization of verbal fluency (VF) cognitive strategies, including clustering, switching, intrusions, and perseverations, within both semantic (SVF) and phonemic (PVF) conditions, across a continuum of neurocognitive decline, spanning from normal cognitive ageing (NC) to mild cognitive impairment (MCI) and its subtypes, amnestic (aMCI) and non-amnestic (naMCI), as well as AD. Materials and Methods: The study sample was derived from the Hellenic Longitudinal Investigation of Aging and Diet (HELIAD) cohort. The sample included 1607 NC individuals, 146 with aMCI (46 single-domain and 100 multi-domain), 92 with naMCI (41 single-domain and 51 multi-domain), and 79 with AD. Statistical analyses, adjusting for sex, age, and education, employed multivariate general linear models to probe differences among these groups. Results: Results showed that AD patients exhibited poorer performance in switching in both VF tasks and SVF clustering compared to NC. Similarly, the aMCI group performed worse than the NC in switching and clustering in both tasks, with aMCI performing similarly to AD, except for SVF switching. In contrast, the naMCI subgroup performed similarly to those with NC across most strategies, surpassing AD patients. Notably, the aMCI subgroup's poor performance in SVF switching was mainly due to the subpar performance of the multi-domain aMCI subgroup. This subgroup was outperformed in switching in both VF tasks by the single-domain naMCI, who also performed better than the multi-domain naMCI in SVF switching. No significant differences emerged in terms of perseverations and intrusions. Conclusions: Overall, these findings suggest a continuum of declining switching ability in the SVF task, with NC surpassing both aMCI and AD, and aMCI outperforming those with AD. The challenges in SVF switching suggest executive function impairment associated with multi-domain MCI, particularly driven by the multi-domain aMCI.

Qualitative Verbal Fluency Components as Prognostic Factors for Developing Alzheimer's Dementia and Mild Cognitive Impairment: Results from the Population-Based HELIAD Cohort

Background and Objectives: The aim of the present study was to investigate the prognostic value of the qualitative components of verbal fluency (clustering, switching, intrusions, and perseverations) on the development of mild cognitive impairment (MCI) and dementia. Materials and Methods: Participants were drawn from the multidisciplinary, population-based, prospective HELIAD (Hellenic Longitudinal Investigation of Aging and Diet) cohort. Two participant sets were separately analysed: those with normal cognition and MCI at baseline. Verbal fluency was assessed via one category and one letter fluency task. Separate Cox proportional hazards regressions adjusted for important sociodemographic parameters were performed for each qualitative semantic and phonemic verbal fluency component. Results: There were 955 cognitively normal (CN), older (72.9 years ±4.9), predominantly female (~60%) individuals with available follow-up assessments after a mean of 3.09 years (±0.83). Among them, 34 developed dementia at follow-up (29 of whom progressed to Alzheimer's dementia (AD)), 160 developed MCI, and 761 remained CN. Each additional perseveration on the semantic condition increased the risk of developing all-cause dementia and AD by 52% and 55%, respectively. Of note, participants with two or more perseverations on the semantic task presented a much more prominent risk for incident dementia compared to those with one or no perseverations. Among the remaining qualitative indices, none were associated with the hazard of developing all-cause dementia, AD, and MCI at follow-up. Conclusions: Perseverations on the semantic fluency condition were related to an increased risk of incident all-cause dementia or AD in older, CN individuals.

Evaluation of Error Production in Animal Fluency and Its Relationship to Frontal Tracts in Normal Aging and Mild Alzheimer's Disease: A Combined LDA and Time-Course Analysis Investigation

Semantic verbal fluency (VF), assessed by animal category, is a task widely used for early detection of dementia. A feature not regularly assessed is the occurrence of errors such as perseverations and intrusions. So far, no investigation has analyzed the how and when of error occurrence during semantic VF in aging populations, together with their possible neural correlates. The present study aims to address the issue using a combined methodology based on latent Dirichlet allocation (LDA) analysis for word classification together with a time-course analysis identifying exact time of errors' occurrence. LDA is a modeling technique that discloses hidden semantic structures based on a given corpus of documents. We evaluated a sample of 66 participants divided into a healthy young group (n = 24), healthy older adult group (n = 23), and group of patients with mild Alzheimer's disease (AD) (n = 19). We performed DTI analyses to evaluate the white matter integrity of three frontal tracts purportedly underlying error commission: anterior thalamic radiation, frontal aslant tract, and uncinate fasciculus. Contrasts of DTI metrics were performed on the older groups who were further classified into high-error rate and low-error rate subgroups. Results demonstrated a unique deployment of error commission in the patient group characterized by high incidence of intrusions in the first 15 s and higher rate of perseverations toward the end of the trial. Healthy groups predominantly showed very low incidence of perseverations. The DTI analyses revealed that the patients with AD committing high-error rate presented significantly more degenerated frontal tracts in the left hemisphere. Thus, our findings demonstrated that the appearance of intrusions, together with left hemisphere degeneration of frontal tracts, is a pathognomic trait of mild AD. Furthermore, our data suggest that the error commission of patients with AD arises from executive and working memory impairments related partly to deteriorated left frontal tracts.

Obsessive-Compulsive and Perseverative Behaviors in Huntington's Disease

Background:

Neuropsychiatric symptoms are highly prevalent in Huntington’s disease (HD). However, little is known of the prevalence and course of obsessive-compulsive behaviors (OCBs) and perseverative behaviors (PBs) during the progression of the disease.

Objective:

This review provides a summary of the literature on OCBs and PBs in HD gene expansion carriers (HDGECs).

Methods:

Pubmed database was searched for articles on OCBs and PBs in HD up to 2017. We used search terms, all synonyms for HD, and various terms for OCBs and PBs.

Results:

We found 5 case series and 11 original articles that describe a prevalence range of 5 to 52% for OCBs and up to 75% for PBs depending on disease stage and measurement scale used. Premanifest HDGECs report more OCBs compared to controls, and manifest HDGECs report a higher rate of OCBs compared to premanifest HDGECs. OCBs and PBs are associated with a longer disease duration and disease severity in manifest HDGECs, but decrease in the most advanced stages. When HDGECs come closer to estimated motor onset, the companion ratings on OCBs appear to be higher than the self-ratings of HDGECs.

Conclusions:

Both OCBs and PBs are characteristic neuropsychiatric features of HD. Perseveration is probably best distinguished from OCBs as it occurs without the individual’s full awareness or insight into their presence (and the behavior may not be distressing). Although these behaviors are seldom distinguished, we conclude that differentiating OCBs from PBs in HD is beneficial for the management and treatment of these symptoms in HDGECs.

Recurrent perseverations on semantic verbal fluency tasks as an early marker of cognitive impairment

INTRODUCTION

Our objective was to examine the association between perseverations produced on the semantic verbal fluency (SVF) task in asymptomatic individuals and the future diagnosis of cognitive impairment (CI).

METHOD

Participants were individuals participating in the Mayo Clinic Study of Aging (N = 1269, M_age = 79.3 years, SD = 5.1; 51% men). All were cognitively normal at baseline and were followed in 15-month intervals for up to 6 visits. Each neurocognitive assessment included SVF tasks ("animals," "fruits," and "vegetables"). Cox modeling was used to test for associations between perseverations and time to CI diagnosis.

RESULTS

Perseverations on the "animals" SVF task were associated with incident CI (hazard ratio = 1.35; 95% confidence interval, CI [1.10, 1.66]). No significant association was found with perseverations on the "fruits" or "vegetables" SVF tasks. Mixed-effects modeling in cognitively normal participants revealed that the number of perseverations at baseline is significantly associated with decline in memory and visuospatial cognitive domains but is not associated with decline in attention.

CONCLUSIONS

Assessing perseverations together with standard SVF scores on the "animals" SVF task can help in early identification of asymptomatic individuals at an increased risk for CI. Perseverations are not associated with attention, but rather visual and verbal working memory mechanisms. In longitudinal settings aimed at early detection of signs of CI in presymptomatic individuals, SVF testing with scoring that includes counting of perseverations may potentially serve as a practical alternative to the more cumbersome memory tests.