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Verbal fluency and brain integrity in behavioral variant FTD
Poster Session B, Friday, September 12, 4:30 - 6:00 pm, Field House
Kyriaki Neophytou1, John Papatriantafyllou2, Kyrana Tsapkini1,3; 1Johns Hopkins School of Medicine, Baltimore, USA, 2Third Age Center IASIS, Athens, Greece, 3Johns Hopkins University, Baltimore, USA
Introduction: The behavioral-variant FTD (bvFTD) is a neurodegenerative disorder primarily characterized by progressive deterioration in personality and social behavior (Rankin et al., 2005). While language and other cognitive abilities are also affected in this population, the relevant research is scarce. A recent study on verbal fluency reported differences in performance between bvFTD individuals, healthy controls, and individuals with Primary Progressive Aphasia (PPA) (a left-hemisphere language-based neurodegenerative disorder) (Van Den Berg et al., 2024). Atrophy in bvFTD is primarily found in the frontal and temporal lobes, with greater right, compared to left, hemisphere atrophy (Kril et al., 2005). Prior research in PPA has shown associations of phonemic fluency with the volume of the left superior temporal regions (STG) and the right middle frontal gyrus (MFG), and of semantic fluency with the left inferior temporal gyrus (ITG) (Riello et al., 2022). This study aimed to investigate the contribution of these bilateral regions, as indexed with cortical thickness, in verbal fluency in bvFTD. Methods: Participants were 46 bvFTD Greek-speaking individuals (age=65.6). Verbal fluency was assessed using (1) Phonemic Fluency and (2) Semantic Fluency (i.e., name as many words as possible from a given category/starting from a given letter in 1-minute). Brain integrity was indexed with average cortical thickness for the bilateral STG, MFG and ITG (i.e., regions previously implicated in verbal fluency). The statistical analysis included simple linear models assessing whether (i) each region, separately for each hemisphere, is associated with verbal fluency and (ii) whether, for a given region, each hemisphere explains unique variance in verbal fluency (i.e., variance explained by one hemisphere, beyond what is accounted for by the contralateral hemisphere). Results: Phonemic Fluency: (i) Statistically significant effects were found for the left MFG (p=0.042) and the left STG (p=0.019). (ii) Statistically/marginally significant unique variance was also explained by these regions: left MGF (p=0.069), left STG (p=0.008). Semantic Fluency: (i) Statistically/marginally significant effects were found for the left MFG (p=0.088), the left STG (p=0.044), and the left ITG (p=0.099). (ii) Statistically/marginally significant unique variance was explained by all three regions (left MGF (p=0.024), left STG (p=0.011), and left ITG (p=0.095)) as well as the right STG (p=0.086). Conclusion: We showed, for the first time, a relationship between verbal fluency and brain integrity (cortical thickness), in bvFTD. Except for one region, all associations were found in the left hemisphere. Importantly, the variance explained by the left-hemisphere regions was unique (i.e., beyond what the respective right-hemisphere regions explained). Compared to previous findings in PPA, the results showed some differences in the extent and laterality of the effects. For Phonological Fluency we found an effect in the left, instead of right MFG. For Semantic Fluency, we showed more widespread left-hemisphere effects and unique variance explained by the right STG. Future analyses will investigate the effect of the laterality of atrophy on these associations. Finally, both fluency scores were associated with the MFG and STG - endpoints of the extreme capsule fasciculus, a white matter tract linked to selective lexical retrieval (Petrides et al., 2002).
Topic Areas: Disorders: Acquired, Language Production