Clustering and switching in verbal fluency: a comparison between control and individuals with brain damage

ABSTRACT Purpose The aim of this study is to analyze and compare the performance and strategies used by control subjects and patients with unilateral brain damage on phonemic and semantic Verbal Fluency tasks. Methods The sample consisted of 104 participants divided into four groups (26 with left hemisphere damage and aphasia- LHDa, 28 with left hemisphere damage and no aphasia- LHDna, 25 with right hemisphere damage- RHD and 25 neurologically healthy control subjects). All participants were administered the phonemic (“M” letter-based) and semantic (animals) verbal fluency tasks from the Montreal-Toulouse Language Assessment Battery (MTL-BR). Results Patients in the LHDa group showed the worst performance (fewer words produced, fewer clusters and switches) in both types of fluency task. RHD group showed fewer switching productions when compared with controls and LHDna had fewer words productions than controls in the first 30 seconds block. Conclusion Our findings suggest that the LHDa group obtained lower scores in most measures of SVF and PVF when compared to the other groups.

Semantic Verbal Fluency in Youth with Down Syndrome: Analysis of Conventional and Contextual Cluster Formation

Expressive language delays and executive functioning challenges are common in youth with Down syndrome (DS). Verbal fluency is one method to investigate these constructs. We examined semantic verbal fluency responses to determine patterns in response generation and the psychometric properties of coded cluster formations. Participants were 97 children and adolescents with DS ranging in age from 6 to 19 years old. The semantic verbal fluency task was administered at two time points, two weeks apart. Heterogeneity in performance was observed for responses when coded either with conventional or contextual classifications. Overall, the number of switches in conventional classifications was greater than contextual classifications. This implies that participants did not use traditional (conventional) categories to organize their semantic verbal fluency responses, but may have been using contextual strategies. However, the number of switches and cluster size variables had poor to moderate test–retest reliability, which indicated that participants did not stay consistent with their performance over the two-week testing interval, regardless of the strategies used. Therefore, conventional and contextual clusters and switches as a measure of executive control may not be appropriate for all individuals with DS and additional attention is warranted to determine the utility of response coding in this population.

Similar Hemodynamic Signal Patterns Between Compact NIRS and 52-Channel NIRS During a Verbal Fluency Task

Multichannel near-infrared spectroscopy (NIRS), including 52-channel NIRS (52ch-NIRS), has been used increasingly to capture hemodynamic changes in the brain because of its safety, low cost, portability, and high temporal resolution. However, optode caps might cause pain and motion artifacts if worn for extended periods of time because of the weight of the cables and the pressure of the optodes on the scalp. Recently, a small NIRS apparatus called compact NIRS (cNIRS) has been developed, and uses only a few flexible sensors. Because this device is expected to be more suitable than 52ch-NIRS in the clinical practice for patients with children or psychiatric conditions, we tested whether the two systems were clinically comparable. Specifically, we evaluated the correlation between patterns of hemodynamic changes generated by 52ch-NIRS and cNIRS in the frontopolar region. We scanned 14 healthy adults with 52ch-NIRS and cNIRS, and measured activation patterns of oxygenated-hemoglobin [oxy-Hb] and deoxygenated-hemoglobin [deoxy-Hb] in the frontal pole while they performed a verbal fluency task. We performed detailed temporal domain comparisons of time-course patterns between the two NIRS-based signals. We found that 52ch-NIRS and cNIRS showed significant correlations in [oxy-Hb] and [deoxy-Hb] time-course changes in numerous channels. Our findings indicate that cNIRS and 52ch-NIRS capture similar task-dependent hemodynamic changes due to metabolic demand, which supports the validity of cNIRS measurement techniques. Therefore, this small device has a strong potential for clinical application with infants and children, as well as for use in the rehabilitation or treatment of patients with psychiatric disorders using biofeedback.

A Toolkit for Analyzing Strategy Use in Phonemic Verbal Fluency Tasks preprint

The phonemic verbal fluency task is a common cognitive assessment of language and executive functioning which asks participants to list as many words as they can that begin with a given letter. Verbal fluency tasks are widely used to identify deficits in verbal fluency, which have been associated with disorders such as schizophrenia and dementia. Verbal fluency tasks are scored by the number of correct responses, however analysis of “clusters” of related words within a response list can give insights into the cognitive strategies used by participants. Unfortunately, manual word cluster analysis is time and labor intensive and inconsistent, since raters may cluster words differently depending on how they themselves have phonetically categorized the words. We present an automated pipeline for quantification of strategy use in the phonemic verbal fluency task, “LetterVF”. LetterVF is a python module (i.e., a script containing useful functions, which can be imported and used in other scripts) that uses a pronunciation dictionary to convert verbal fluency task data items into lists of phonemes, which can be analyzed to identify clusters of words that share similarities in any of several clustering categories. Additionally, LetterVF contains useful functions for identifying intrusions (words which do not follow the rules for the task), identifying perseverations (responses repeated within the same trial), counting the number of cluster switches in a list, and calculating the average size of clusters for a list. Analysis of data from 50 participants’ verbal fluency task responses indicated that analysis using LetterVF yields accuracy and consistency on par with manual analysis. Our hope is that this tool will allow researchers to get more out of their datasets, and explore new topics related to cognitive strategy use, such as how strategies change with age and differences in strategies between experimental groups.

10-Hz tACS Over The Prefrontal Cortex Improves Phonemic Fluency

Verbal fluency is an important indicator of human verbal ability. Methods to improve fluency is an interesting issue necessitating investigation. To do this, the current study required participants to randomly receive transcranial alternating current stimulation (tACS) at 10 Hz, 40 Hz (control frequency), and sham stimulation over the prefrontal cortex before a phonemic fluency task. It was found that 10-Hz tACS significantly improved phonemic fluency relative to sham stimulation. This result demonstrates the modulatory effect of 10-Hz tACS on language ability.

Word Fluency Test Performance in Primary Progressive Aphasia and Primary Progressive Apraxia of Speech

Purpose This study compared performance on three-word fluency measures among individuals with primary progressive aphasia (PPA) and primary progressive apraxia of speech (PPAOS), and examined the relationship between word fluency and other measures of language and speech. Method This study included 106 adults with PPA and 30 adults with PPAOS. PPA participants were divided into three clinical subgroups: semantic (svPPA), logopenic (lvPPA), and nonfluent/agrammatic with or without apraxia of speech (nfPPA). Category fluency, letter fluency, and action/verb fluency tasks were administered to all participants. Results The four clinical groups performed abnormally on the word fluency measures, although not to a degree that represented high sensitivity to their PPA or PPAOS diagnosis. All PPA subgroups produced fewer words compared to individuals with PPAOS on all word fluency measures. Moderate correlations were found between word fluency and aphasia severity and naming performance in some of the clinical groups. Conclusions Word fluency measures are often challenging for individuals with PPA and PPAOS, but they are not of equal difficulty, with letter fluency being the most difficult. Differences among word fluency tests also vary to some degree as a function of the clinical group in question, with least impairment in PPAOS. However, the findings of this study do not support statistically significant differences in word fluency task performance among the PPA subgroups. Correlations suggest that word fluency performance in PPA is at least partly related to aphasia severity.

Lexical-semantic Properties in Parkinson's Disease with and without Dementia

Dementia has important clinical consequences for patients with PD and their caregivers, which may negatively, affected their daily living activities and quality of life. Previous studies, have investigated the properties and characteristics of the words generated in semantic fluency task by patients with Alzheimer's disease, but this has not been investigated in PD patients yet. This study aimed to investigate if there are possible distinctive features that might differentiate between cognitive decline direct consequence of Idiopathic PD and that of Alzheimer’s type dementia associated with PD. There were six PD patients with dementia, six matched PD patients without dementia and six matched controls participated in this study. The present findings showed that although patients with dementia performed worse than those without dementia on all neuropsychological tests, significant differences were found only on the semantic fluency test and Frontal assessment battery. Furthermore, the present findings showed that patients with dementia produced fewer words in the semantic fluency task than healthy controls did. The words generated by demented patients were longer, less familiar, less typical and acquired later in life than the words produced by healthy controls. These findings might use for clinical application to distinct between PD patients with and without dementia.