Zahn Roland, Moll Jorge, Iyengar Vijeth, Huey Edward D, Tierney Michael, Krueger Frank, Grafman Jordan
National Institutes of Health, National Institutes of Neurological Disorders and Stroke, Cognitive Neuroscience Section, Bethesda, MD 20892-1440, USA.
Brain. 2009 Mar;132(Pt 3):604-16. doi: 10.1093/brain/awn343. Epub 2009 Jan 19.
Inappropriate social behaviours are early and distinctive symptoms of the temporal and frontal variants of frontotemporal lobar degeneration (FTLD). Knowledge of social behaviour is essential for appropriate social conduct. It is unknown, however, in what way this knowledge is degraded in FTLD. In a recent functional MRI study, we have identified a right-lateralized superior 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 describing less 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 and feelings associated with these social concepts. Here, we investigated whether the right superior sector of the aTL is necessary for context-independent knowledge of social concepts. We assessed neuronal glucose uptake using 18-fluoro-deoxy-glucose-positron emission tomography (FDG-PET) and a novel semantic discrimination task which probed knowledge of social and animal function concepts in patients with FTLD (n = 29) and corticobasal syndrome (n = 18). FTLD and corticobasal syndrome groups performed equally poorly on animal function concepts but FTLD patients showed more pronounced impairments on social concepts than corticobasal syndrome patients. FTLD patients with right superior aTL hypometabolism, as determined on individual ROI analyses, were significantly more impaired on social concepts than on animal function concepts. FTLD patients with selective impairments for social concepts, as determined on individual neuropsychological profiles, showed higher levels of inappropriate social behaviours ('disinhibition') and demonstrated more pronounced hypometabolism in the right superior aTL, the left temporal pole and the right lateral orbitofrontal and dorsomedial prefrontal cortex as compared with FTLD patients showing selective impairments of animal function concepts. Combining both FTLD subgroup analyses, based on anatomical and neuropsychological criteria, by using inclusive masks, revealed the right superior aTL as associated with selective impairments of social concepts in both analyses. These results corroborate the hypothesis that the right aTL is necessary for representing conceptual social knowledge. Further, we provide first evidence for the potential importance of conceptual social knowledge impairments as contributing to behavioural symptoms of FTLD.
不适当的社会行为是额颞叶变性（FTLD）的颞叶和额叶变异型的早期且独特的症状。社会行为知识对于恰当的社会行为至关重要。然而，目前尚不清楚在FTLD中这种知识是以何种方式退化的。在最近一项功能磁共振成像（fMRI）研究中，我们发现了一个右侧优势的颞上叶前部（aTL）区域，与描述社会关联度较低的动物行为的概念（“动物功能概念”：例如“可训练的”“有营养的”）相比，该区域对“社会概念”（即描述社会行为的概念：例如“礼貌的”“吝啬的”）表现出选择性激活。在另一项fMRI研究中，颞上叶前部的激活与这些社会概念相关的动作和情感背景无关。在此，我们研究了颞上叶前部的右侧优势区域对于社会概念的背景独立知识是否必要。我们使用18氟脱氧葡萄糖正电子发射断层扫描（FDG-PET）和一项新颖的语义辨别任务评估了神经元葡萄糖摄取，该任务探究了FTLD患者（n = 29）和皮质基底节综合征患者（n = 18）对社会和动物功能概念的知识。FTLD组和皮质基底节综合征组在动物功能概念方面表现同样差，但FTLD患者在社会概念方面的损害比皮质基底节综合征患者更明显。根据个体感兴趣区域（ROI）分析确定为右侧颞上叶前部代谢减低的FTLD患者，在社会概念方面的损害显著大于动物功能概念方面。根据个体神经心理学特征确定为对社会概念有选择性损害的FTLD患者，与对动物功能概念有选择性损害的FTLD患者相比，表现出更高水平的不适当社会行为（“去抑制”），并且在右侧颞上叶前部、左侧颞极以及右侧外侧眶额和背内侧前额叶皮质表现出更明显的代谢减低。通过使用包容性掩膜，结合基于解剖学和神经心理学标准的FTLD亚组分析，在两项分析中均显示右侧颞上叶前部与社会概念的选择性损害相关。这些结果证实了右侧颞上叶前部对于表征概念性社会知识是必要的这一假设。此外，我们首次提供了概念性社会知识损害对FTLD行为症状有潜在重要影响的证据。
