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- DOI: 10.1093/brain/awn343
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Social conceptual impairments in frontotemporal lobar degeneration with right anterior temporal hypometabolism
Zahn R, Moll J, Iyengar V, Huey Edward, Tierney M, Krueger Frank, Grafman Jordan
Brain. 2009;132(3):604-616.
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Full-text held externally
- DOI: 10.1093/brain/awn343
Abstract
Inappropriate social behaviours are early and distinctive symptoms of the temporal andfrontal variants of frontotemporal lobar degeneration (FTLD). Knowledge of social behaviour isessential for appropriate social conduct. It is unknown, however, in what way this knowledge isdegraded in FTLD. In a recent functional MRI study we have identified a right-lateralizedsuperior anterior temporal lobe (aTL) region showing selective activation for social concepts (i.e.concepts describing social behaviour: e.g. polite, stingy) as compared with concepts describingless socially relevant animal behaviour (animal function concepts: e.g. trainable,nutritious). In a further fMRI study, superior aTL activation was independent of the context of actions andfeelings associated with these social concepts. Here, we investigated whether the right superiorsector of the aTL is necessary for context-independent knowledge of social concepts. We assessedneuronal glucose uptake using 18-Fluoro-Deoxy-Glucose-Positron Emission Tomography (FDGPET)and a novel semantic discrimination task which probed knowledge of social and animalfunction concepts in patients with FTLD (N=29) and corticobasal syndrome (CBS, N=18). FTLDand CBS groups performed equally poorly on animal function concepts but FTLD patients showedmore pronounced impairments on social concepts than CBS patients. FTLD patients with rightsuperior aTL hypometabolism, as determined on individual ROI analyses, were significantly moreimpaired on social concepts than on animal function concepts. FTLD patients with selectiveimpairments for social concepts, as determined on individual neuropsychological profiles, showedhigher levels of inappropriate social behaviours (disinhibition) and demonstrated morepronounced hypometabolism in the right superior aTL, the left temporal pole and the right lateralorbitofrontal and dorsomedial prefrontal cortex as compared with FTLD patients showing selectiveimpairments of animal function concepts. Combining both FTLD subgroup analyses, based onanatomical and neuropsychological criteria, by using inclusive masks, revealed the right superioraTL as associated with selective impairments of social concepts in both analyses. These resultscorroborate the hypothesis that the right aTL is necessary for representing conceptual socialknowledge. Further, we provide first evidence for the potential importance of conceptual socialknowledge impairments as contributing to behavioural symptoms of FTLD.