Architecture and anatomy of executive processes: evidence from verbal fluency and Trail Making Test in 2009 stroke patients.

OBJECTIVES: The few voxel-wise lesion-symptom mapping (VLSM) studies aimed at identifying the anatomy of executive function are limited by the absence of a model and by small populations. Using Trail Making Test (TMT) and verbal fluency and a model of their architectures, our objective was to identify the key structures underlying two major executive processes, set-shifting and strategic word search. METHODS: We applied a validated VLSM analysis to harmonized cognitive and imaging data from 2009 ischemic stroke patients as a part of the Meta VCI Map consortium. All contrast analyses used an adjusted threshold with 2000 Freedman-Lane permutations (p ≤ 0.05). RESULTS: The TMT parts A and B were associated with structures involved in visual-spatial processing, the motor system, the frontal lobes, and their subcortical connections. Set-shifting depended on the left dorsomedial frontal region. Both semantic and phonemic fluency tests depended on verbal output abilities and processing speed with similar slopes in different languages. The strategic search process depended on Broca's area, F2 and related tracts, temporal and deep regions. Lastly, the lesion map of set-shifting did not overlap with those of strategic word search processes. INTERPRETATION: Our results identify the anatomical substrates of two main executive processes, revealing that they represent only a specific subpart of previously reported structures. Finally, our results indicate that executive functions depend on several specific, anatomically separable executive processes mainly operating in various parts of the frontal lobes.

Screening for Cognitive Impairment in Bilinguals: What Is the Influence of the Language of Assessment?

BACKGROUND: Bilingualism's impact on cognitive assessment remains underexplored. This study analyzes the efficacy of the Mini-Mental State Examination (MMSE) as a screening tool for bilinguals, specifically examining the influence of language choice on balanced and unbalanced Lebanese bilinguals (Arabic-French) and its implications for diagnosing cognitive impairment. METHODS: Ninety-three bilingual healthy controls (mean age = 67.99 ± 9.3) and 29 Alzheimer's disease patients (mean age = 77.2 ± 5.9), including 26 with mild and 3 with moderate dementia, underwent MMSE assessments in both Arabic and French. The study aimed to assess language impact on cognitive screening outcomes in different bilingual subtypes. RESULTS: Sensitivity in screening for cognitive impairment using the MMSE varied based on language and bilingualism subtype. For unbalanced bilinguals, using the prominent language increased sensitivity. Conversely, in balanced bilinguals, employing the societal majority language enhanced sensitivity. This suggests that the conventional use of the non-prominent language in cognitive screening for foreigners/immigrants may result in a subtle loss of MMSE sensitivity. CONCLUSION: This study emphasizes the critical role of language choice in cognitive assessment for bilinguals. The MMSE's sensitivity is influenced by language selection, with clinical implications for screening procedures. Recommendations include using the prominent language for cognitive screening in dominant bilinguals and the societal majority language for balanced bilinguals. This nuanced approach aims to improve the accuracy and cultural sensitivity of cognitive screening in bilingual populations, addressing the gap in current assessment practices.

Verbal fluency in bilingual Lebanese adults: Is the prominent language advantage due to executive processes, language processes, or both?

Although bilingualism is widespread, little data on verbal fluency tasks (VFTs) within bilingualism subtypes and the underlying mechanisms exist. The study's objective was to explore executive and language processes in 10 semantic and letter VFTs and a set of language and executive tests among 100 elderly Arabic-French bilinguals from three bilingualism subgroups: Arabic-dominant, French-dominant, and balanced. We observed a prominent-language advantage for semantic and letter VFTs in French but not for letter VFTs in Arabic. This advantage in the VFT was associated with a sustained rate of late production, a higher percentage of specific words, a higher number of clusters, and a larger cluster size, and was related mainly to language processes. Our results suggest that the strategic search processes underlying VFTs operate on the two phonological output lexicons of bilinguals with similar characteristics in different languages and thus support the hypothesis of a single, centralized, strategic search process.

Functional architecture of executive processes: Evidence from verbal fluency and lesion mapping in stroke patients.

The functional organization and related anatomy of executive functions are still largely unknown and were examined in the present study using a verbal fluency task. The objective of this study was to determine the cognitive architecture of a fluency task and related voxelwise anatomy in the GRECogVASC cohort and fMRI based meta-analytical data. First, we proposed a model of verbal fluency in which two control processes, lexico-semantic strategic search process and attention process, interact with semantic and lexico-phonological output processes. This model was assessed by testing 404 patients and 775 controls for semantic and letter fluency, naming, and processing speed (Trail Making test part A). Regression (R2 = .276 and .3, P = .0001, both) and structural equation modeling (CFI: .88, RMSEA: .2, SRMR: .1) analyses supported this model. Second, voxelwise lesion-symptom mapping and disconnectome analyses demonstrated fluency to be associated with left lesions of the pars opercularis, lenticular nucleus, insula, temporopolar region, and a large number of tracts. In addition, a single dissociation showed specific association of letter fluency with the pars triangularis of F3. Disconnectome mapping showed the additional role of disconnection of left frontal gyri and thalamus. By contrast, these analyses did not identify voxels specifically associated with lexico-phonological search processes. Third, meta-analytic fMRI data (based on 72 studies) strikingly matched all structures identified by the lesion approach. These results support our modeling of the functional architecture of verbal fluency based on two control processes (strategic search and attention) operating on semantic and lexico-phonologic output processes. Multivariate analysis supports the prominent role of the temporopolar area (BA 38) in semantic fluency and the F3 triangularis area (BA 45) in letter fluency. Finally, the lack of voxels specifically dedicated to strategic search processes could be due to a distributed organization of executive functions warranting further studies.