Why Almost Always Animals? Ranking Fluency Tasks for the Detection of Dementia Based on Receiver Operating Characteristic (ROC) and Quality ROC Analyses

Application of the Semantic Fluency Test in the Screening of Mandarin-Chinese-Speaking Older Adults with Mild Dementia of the Alzheimer Type

Semantic fluency tests have been widely used as a screening test for dementia of Alzheimer type. However, few studies have explored the application of semantic fluency tests in Mandarin Chinese speakers. This study aimed to explore the feasibility of using different semantic fluency test categories to distinguish between older adults without cognitive impairments and those with dementia of Alzheimer type in Taiwan. A total of 58 healthy older adults and 54 individuals with dementia of Alzheimer type were recruited. Semantic categories of "animals", "fruits", "vegetables", "birds", "means of transportations" and "musical instruments" were administered to participants. The scores from two groups of participants for each category were analyzed. Significant differences in the test scores of each category between two groups of participants were found. The results also revealed that the variables related to whether the participant had dementia, gender, age, and years of schooling significantly influenced the semantic fluency scores for each category. Among all the demographic characteristic of participants, the diagnosis of dementia was the most determining factor. Furthermore, this study proposed optimal cutoff points and calculated the AUC for various test durations (i.e., 30 s, 45 s and 60 s) and semantic categories in the semantic fluency test, which may serve as a reference that would help clinical personnel distinguish between older adults without cognitive impairments and those with dementia of Alzheimer type in Taiwan.

Semantic fluency reveals reduced functional connectivity between subcategorical co-hyponyms in recent-onset inpatients with first-episode psychosis

Data on clustering and switching during semantic fluency (SF) in patients with first-episode psychosis (PwFEP) are scant. We aimed to investigate (1) clustering and switching on SF in PwFEP using more detailed clustering analyses and (2) the possibility of disproportionate clustering deficits across different SF tasks in PwFEP and healthy subjects (HS), with the latter being suggested by the current literature on patients with schizophrenia. We recruited 22 Croatian-speaking PwFEP with schizophrenia features or symptoms and 22 HS matched in age, sex distribution, and handedness. All patients were medicated and had a mean illness duration of 1 month. The categories animals, trees, vegetables, fruits, and musical instruments were administered for SF. PwFEP produced significantly fewer correct words in the aggregate score, as well as across all categories. The switching rate was significantly higher in PwFEP, but no post hoc comparisons were significant. PwFEP also produced significantly smaller clusters, yet the post hoc comparisons for the tree and fruit task were not significant. A higher switching rate and smaller clusters indicate less efficient functional connectivity within subcategories of the given categories, but not necessarily between the subcategories. Although both less likely to produce a cluster once a switch has been uttered and less likely to produce clusters larger than two words compared to HS, the latter deficit was more pronounced. Our results further suggest that PwFEP might show normal clustering performance on some SF tasks. We discuss the results in the context of the hypothesis of semantic hyperactivation in psychoses.

Knowledge Representations Derived From Semantic Fluency Data

The semantic fluency task is commonly used as a measure of one’s ability to retrieve semantic concepts. While performance is typically scored by counting the total number of responses, the ordering of responses can be used to estimate how individuals or groups organize semantic concepts within a category. I provide an overview of this methodology, using Alzheimer’s disease as a case study for how the approach can help advance theoretical questions about the nature of semantic representation. However, many open questions surrounding the validity and reliability of this approach remain unresolved.

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.

Spoken Word Segmentation in First and Second Language: When ERP and Behavioral Measures Diverge

Previous studies of word segmentation in a second language have yielded equivocal results. This is not surprising given the differences in the bilingual experience and proficiency of the participants and the varied experimental designs that have been used. The present study tried to account for a number of relevant variables to determine if bilingual listeners are able to use native-like word segmentation strategies. Here, 61 French-English bilingual adults who varied in L1 (French or English) and language dominance took part in an audiovisual integration task while event-related brain potentials (ERPs) were recorded. Participants listened to sentences built around ambiguous syllable strings (which could be disambiguated based on different word segmentation patterns), during which an illustration was presented on screen. Participants were asked to determine if the illustration was related to the heard utterance or not. Each participant listened to both English and French utterances, providing segmentation patterns that included both their native language (used as reference) and their L2. Interestingly, different patterns of results were observed in the event-related potentials (online) and behavioral (offline) results, suggesting that L2 participants showed signs of being able to adapt their segmentation strategies to the specifics of the L2 (online ERP results), but that the extent of the adaptation varied as a function of listeners' language experience (offline behavioral results).

What Drives Task Performance During Animal Fluency in People With Alzheimer's Disease?

Background

Animal fluency is a widely used task to assess people with Alzheimer’s disease (AD) and other neurological disorders. The mechanisms that drive performance in this task are argued to rely on language and executive functions. However, there is little information regarding what specific aspects of these cognitive processes drive performance on this task.

Objective

To understand which aspects of language (i.e., semantics, phonological output lexicon, phonological assembly) and executive function (i.e., mental set shifting; information updating and monitoring; inhibition of possible responses) are involved in the performance of animal fluency in people with AD.

Methods

Animal fluency data from 58 people with probable AD from the DementiaBank Pittsburgh Corpus were analyzed. Number of clusters and switches were measured and nine word properties (e.g., frequency, familiarity) for each of the correct words (i.e., each word counting toward the total score, disregarding non-animals and repetitions) were determined. Random forests were used to understand which variables predicted the total number of correct words, and conditional inference trees were used to search for interactions between the variables. Finally, Wilcoxon tests were implemented to cross-validate the results, by comparing the performance of participants with scores below the norm in animal fluency against participants with scores within the norm based on a large normative sample.

Results

Switches and age of acquisition emerged as the most important variables to predict total number of correct words in animal fluency in people with AD. Cross-validating the results, people with AD whose animal fluency scores fell below the norm produced fewer switches and words with lower age of acquisition than people with AD with scores in the normal range.

Conclusion

The results indicate that people with AD rely on executive functioning (information updating and monitoring) and language (phonological output lexicon, not necessarily semantics) to produce words on animal fluency.