Integrating verbal fluency with executive functions: Evidence from twin studies in adolescence and middle age.
ABSTRACT: The relationship of verbal fluency to executive functions (EFs) remains somewhat unclear. Verbal fluency is sometimes considered an EF ability, but is not often included in the same models as other well-studied EFs (inhibition, shifting, and working memory updating). We examined the associations between verbal fluency and EFs at 2 ages with the unity/diversity model, which includes common and domain-specific EF factors. Participants were 813 adolescent twins from the Colorado Longitudinal Twin Sample (mean age 17 years) and 1,290 middle-aged twins from the Vietnam Era Twin Study of Aging (mean age 56 years) who completed multiple measures of EFs, verbal fluency, vocabulary, and nonverbal cognitive ability. Results revealed that, in both samples, a General Fluency factor (i.e., comprising both phonemic and semantic fluency measures) was associated with the Common EF factor, but also with variance unique to working memory updating, working memory span, and set-shifting. In adolescents, semantic fluency also had unique associations with shifting beyond its shared variance with phonemic fluency and Common EF. After accounting for EFs and other cognitive abilities, there were unique genetic and environmental influences on the General Fluency and Semantic-Specific latent factors. These results suggest that verbal fluency ability may best be viewed as an amalgamation of general EF variance (i.e., Common EF ability), variance shared with other EFs (e.g., Updating-Specific ability), and multiple sources of unique genetic/environmental variance (i.e., General Fluency and Semantic-Specific abilities). These associations between verbal fluency and EFs generalize to populations that differ in age by approximately 40 years. (PsycINFO Database Record (c) 2019 APA, all rights reserved).
Project description:Verbal and figural fluency are related to executive functions (EFs), but the extent to which they benefit from executive resources and their respective cortical representations is not clear. Moreover, different brain areas and cognitive functions are involved in fluency processing. This study investigated effects of modulation of cortical excitability in the left dorsolateral prefrontal cortex (l-DLPFC), left temporal area and right posterior parietal cortex (r-PPC) with transcranial direct current stimulation (tDCS), on verbal and figural fluency. Fifteen healthy adult participants received anodal l-DLPFC (F3), anodal left temporal (T3), anodal r-PPC (P4) and sham tDCS (15?min, 1.5?mA). After five minutes of stimulation, participants underwent the verbal fluency (i.e., semantic and phonemic fluency tasks) and figural fluency tasks. Participants significantly generated more words with phonemic cues during anodal l-DLPFC tDCS and more words with semantic cues during both anodal left temporal and anodal l-DLPFC tDCS. In contrast, they generated more unique figures under anodal r-PPC and anodal l-DLPFC tDCS. Our results implicate that prefrontal regions and EFs are shared anatomical correlates and cognitive processes relevant for both, verbal and figural fluency (supramodal contribution of DLPFC activation), whereas r-PPC and left temporal cortex are more specifically involved in figural and semantic fluency (modality-specific contribution).
Project description:BACKGROUND: The processing of verbal fluency tasks relies on the coordinated activity of a number of brain areas, particularly in the frontal and temporal lobes of the left hemisphere. Recent studies using functional magnetic resonance imaging (fMRI) to study the neural networks subserving verbal fluency functions have yielded divergent results especially with respect to a parcellation of the inferior frontal gyrus for phonemic and semantic verbal fluency. We conducted a coordinate-based activation likelihood estimation (ALE) meta-analysis on brain activation during the processing of phonemic and semantic verbal fluency tasks involving 28 individual studies with 490 healthy volunteers. RESULTS: For phonemic as well as for semantic verbal fluency, the most prominent clusters of brain activation were found in the left inferior/middle frontal gyrus (LIFG/MIFG) and the anterior cingulate gyrus. BA 44 was only involved in the processing of phonemic verbal fluency tasks, BA 45 and 47 in the processing of phonemic and semantic fluency tasks. CONCLUSIONS: Our comparison of brain activation during the execution of either phonemic or semantic verbal fluency tasks revealed evidence for spatially different activation in BA 44, but not other regions of the LIFG/LMFG (BA 9, 45, 47) during phonemic and semantic verbal fluency processing.
Project description:Disproportionately greater deficits in semantic relative to phonemic verbal fluency are seen in Alzheimer's disease (AD) and have been attributed to neurodegenerative changes in the temporal lobe. Amnestic (AMN) mild cognitive impairment (MCI), which often represents incipient AD, is also characterized by early temporal lobe neuropathology, but previous comparisons of verbal fluency between AD and AMN MCI have yielded mixed results. We examined semantic and phonemic verbal fluency performance in 399 individuals (78 AD, 138 AMN MCI, 72 non-amnestic MCI, and 111 cognitively normal controls). Similar verbal fluency patterns were seen in AMN MCI and AD; both groups exhibited disproportionately poorer performance on semantic verbal fluency relative to normal controls. However, relative verbal fluency indices performed more poorly than individual semantic or phonemic verbal fluency indices for discriminating AMN MCI or AD participants from normal controls, suggesting that they are unlikely to provide additional utility for predicting progression from MCI to AD.
Project description:Depression is associated with deficits in executive functions (EFs)-cognitive control abilities that regulate goal-directed thoughts and actions-but the etiology of these associations is unclear. We examined the relations between depressive symptoms and multiple EF latent variables in a population-based sample of 439 twin pairs assessed at mean ages 12, 17, and 23 years. Greater depressive symptoms negatively related to a Common EF factor capturing shared variance across response inhibition, working memory updating, and mental set shifting tasks, and also negatively related to an Updating-Specific factor, but not a Shifting-Specific factor. Cross-lagged panel models suggested that the Common EF correlations reflected within-wave associations rather than prospective effects, whereas the Updating-Specific correlations reflected associations of earlier depression levels with later Updating-Specific ability. Twin models were consistent with a model in which Common EF and Updating-Specific abilities relate to depression through correlated genetic risk, with no significant environmental correlations.
Project description:Objective: Numerous reports on neurocognitive functioning deficits in individuals at clinical high risk (CHR) and first-episode psychosis (FEP) patients suggest particular deficits in executive functioning (EF). However, to date, most of the studies have administered a single or a few EF tests to participants, and few investigations have examined the different components of EF to identify specific subdomains of relative strength and weakness. Method: Forty CHR subjects, 85 FEP patients, and 85 healthy controls (HCs) were assessed with a neuropsychological battery to elucidate the profiles of EF in the subdomains of shift, attention, fluency, and planning. Results: In the subdomains of shift, attention, and fluency, CHR individuals and FEP patients showed deficits compared to HC. The post hoc analysis revealed that CHR individuals had comparable attention shifting and phonemic fluency compared to FEP. CHR showed intermediate deficits between FEP and HCs in spatial working memory and semantic fluency, and the largest effect size was observed in semantic fluency both for CHR and FEP. Conclusion: Overall, the findings of this study, in addition to providing detailed profiles of EF in prodromal and early psychosis patients, highlight the informative value of the specific subdomains of semantic fluency and spatial working memory.
Project description:This exploratory latent-variable study sought to identify common sources of variance between two multifaceted sets of constructs: executive functions (EFs) and negative thoughts/affect. One-hundred ninety-two college students completed nine tasks representing three types of EFs (inhibition, updating, and shifting) and a set of questionnaires assessing four facets of negative thought/affect (anxiety symptoms, depression symptoms, worry, and rumination). Results indicated that, although the four negative thought/affect constructs were substantially correlated with one another, trait worry was the construct uniquely associated with EFs. Specifically, worry was associated with general EF abilities underlying all three subtypes of EFs (common EF), but was not associated with specific EF abilities (i.e., shifting-specific and updating-specific). These findings highlight the importance of partitioning common and specific variances in both EFs and negative thought/affect when examining the associations between these two research domains. (PsycInfo Database Record (c) 2020 APA, all rights reserved).
Project description:BACKGROUND:Verbal fluency deficits are common in patients with Parkinson's disease. The association of these impairments with regional neuropathological changes is unexplored. OBJECTIVES:Determine if patients with verbal fluency impairments have greater neuropathological burden in frontal, temporal, and limbic regions and if Lewy bodies or neurofibrillary tangles were associated with verbal fluency impairments. METHODS:Data was derived from the Arizona Study of Aging and Neurodegenerative Disorders. 47 individuals who completed phonemic and semantic verbal fluency tasks and met clinicopathological criteria for Parkinson's disease (with and without comorbid Alzheimer's disease) were included. Impairment on fluency tasks was defined by normative data, and the density of neuropathology in temporal, limbic, and frontal regions was compared between groups. RESULTS:Individuals with semantic fluency impairments had greater total pathology (Lewy bodies + neurofibrillary tangles) in limbic structures (W = 320.0, p?=?.033, rpb?=?.33), while those who had phonemic fluency impairments had increased total neuropathology in frontal (W?=?364.5, p?=?.011, rpb?=?.37), temporal (W?=?356.5, p?=?.022, rpb?=?.34), and limbic regions (W?=?357.0, p?=?.024, rpb?=?.34). Greater Lewy body density was found in those with verbal fluency impairments, though trends for greater neurofibrillary tangle density were noted as well. CONCLUSIONS:Impaired phonemic fluency was associated with higher Lewy body and tangle burden in frontal, temporal, and limbic regions, while impaired semantic fluency was associated with greater limbic pathology. Though neurofibrillary tangles trended higher in several regions in those with impaired verbal fluency, higher Lewy body density in general was associated with verbal fluency deficits. Implications for research and clinical practice are discussed.
Project description:Bilinguals often show a disadvantage in lexical access on verbal fluency tasks wherein the criteria require the production of words from semantic categories. However, the pattern is more heterogeneous for letter (phonemic) fluency wherein the task is to produce words beginning with a given letter. Here, bilinguals often outperform monolinguals. One explanation for this is that phonemic fluency, as compared with semantic fluency, is more greatly underpinned by executive processes and that bilinguals exhibit better performance on phonemic fluency due to better executive functions. In this study, we re-analyzed phonemic fluency data from the Betula study, scoring outputs according to two measures that purportedly reflect executive processes: clustering and switching. Consistent with the notion that bilinguals have superior executive processes and that these can be used to offset a bilingual disadvantage in verbal fluency, bilinguals (35-65 years at baseline) demonstrated greater switching and clustering throughout the 15-year study period.
Project description:Verbal fluency is the ability to retrieve lexical knowledge quickly and efficiently and develops during childhood and adolescence. Few studies have investigated associations between verbal fluency performance and brain structural variation in children. Here we examined associations of verbal fluency performance with structural measures of frontal and temporal language-related brain regions and their connections in 73 typically-developing children aged 7-13 years. Tract-based spatial statistics was used to extract fractional anisotropy (FA) from the superior longitudinal fasciculus/arcuate fasciculus (SLF/AF), and the white matter underlying frontal and temporal language-related regions. FreeSurfer was used to extract cortical thickness and surface area. Better semantic and phonemic fluency performance was associated with higher right SLF/AF FA, and phonemic fluency was also modestly associated with lower left SLF/AF FA. Explorative voxelwise analyses for semantic fluency suggested associations with FA in other fiber tracts, including corpus callosum and right inferior fronto-occipital fasciculus. Overall, our results suggest that verbal fluency performance in children may rely on right hemisphere structures, possibly involving both language and executive function networks, and less on solely left hemisphere structures as often is observed in adults. Longitudinal studies are needed to clarify whether these associations are mediated by maturational processes, stable characteristics and/or experience.
Project description:The decrease in verbal fluency in patients with Parkinson's disease (PD) undergoing subthalamic nucleus deep brain stimulation (STN-DBS) is usually assumed to reflect a frontal lobe-related cognitive dysfunction, although evidence for this is lacking.To explore its underlying mechanisms, we combined neuropsychological, psychiatric and motor assessments with an examination of brain metabolism using F-18 fluorodeoxyglucose positron emission tomography, in 26 patients with PD, 3 months before and after surgery. We divided these patients into two groups, depending on whether or not they exhibited a postoperative deterioration in either phonemic (10 patients) or semantic (8 patients) fluency. We then compared the STN-DBS groups with and without verbal deterioration on changes in clinical measures and brain metabolism.We did not find any neuropsychological change supporting the presence of an executive dysfunction in patients with a deficit in either phonemic or semantic fluency. Similarly, a comparison of patients with or without impaired fluency on brain metabolism failed to highlight any frontal areas involved in cognitive functions. However, greater changes in cognitive slowdown and apathy were observed in patients with a postoperative decrease in verbal fluency.These results suggest that frontal lobe-related cognitive dysfunction could play only a minor role in the postoperative impairment of phonemic or semantic fluency, and that cognitive slowdown and apathy could have a more decisive influence. Furthermore, the phonemic and semantic impairments appeared to result from the disturbance of distinct mechanisms.