Social Cognition and its Neuroanatomic Correlates in Frontotemporal Dementia

Abstract Objective Frontotemporal dementia (FTD) often presents with impaired social cognition in both the behavioral and language variants. Establishing reliable measures and neural correlates of social cognition may aid in staging and monitoring FTD subtypes. Here, we examined group differences in social cognitive measures between FTD subtypes and cortical thickness correlates of social cognition across groups. Method Participants with behavioral variant FTD (n = 53; bvFTD), semantic variant primary progressive aphasia (n = 32; svPPA) and non-fluent variant PPA (n = 32; nfPPA) were enrolled in the Frontotemporal Lobar Degeneration Neuroimaging Initiative (NIFD). In first-visit data, we examined group differences in social cognition measures [Interpersonal Reactivity Index (IRI), Revised Social-Monitoring Scale (RSMS), and Behavioral Inhibition/Activation (BIS/BAS) Scales]. We used multivariate regression adjusted for age, total intracranial volume, and CDR global score to explore associations between social cognition and cortical thickness in pre-specified regions. Results Reduced perspective-taking and sensitivity to socio-emotional expressiveness was observed in early-stage bvFTD and svPPA groups compared to the nfPPA group. Across FTD cohorts, increased perspective-taking was associated with reduced cortical thickness of regions within the salience and default mode networks. Increased empathic concern was associated with increased left inferior parietal cortical thickness. Increased behavioral inhibition was associated with reduced right posterior cingulate cortical thickness. Increased behavioral activation was associated with reduced right pars triangularis cortical thickness. Conclusions Social cognition is affected in early-stage bvFTD and svPPA to a greater extent than nfPPA. Neural correlates of social cognition are varied and warrant additional study as our findings contrast with previous literature that has typically linked lower perspective-taking with atrophy.