Indirect speech acts—responding “I forgot to wear my watch today” to someone who asked for the time—are ubiquitous in daily conversation, but are understudied in current neurobiological models of language. To comprehend an indirect speech act like this one, listeners must not only decode the lexical-semantic content of the utterance, but also make a pragmatic, bridging inference. This inference allows listeners to derive the speaker’s true, intended meaning—in the above dialog, for example, that the speaker cannot provide the time. In the present work, we address this major gap by asking non-aphasic patients with behavioral variant frontotemporal dementia (bvFTD, n = 21) and brain-damaged controls with amnestic mild cognitive impairment (MCI, n = 17) to judge simple question-answer dialogs of the form: “Do you want some cake for dessert?” “I’m on a very strict diet right now,” and relate the results to structural and diffusion MRI. Accuracy and reaction time results demonstrate that subjects with bvFTD, but not MCI, are selectively impaired in indirect relative to direct speech act comprehension, due in part to their social and executive limitations, and performance is related to caregivers’ judgment of communication efficacy. MRI imaging associates the observed impairment in bvFTD to cortical thinning not only in traditional language-associated regions, but also in fronto-parietal regions implicated in social and executive cerebral networks. Finally, diffusion tensor imaging analyses implicate white matter tracts in both dorsal and ventral projection streams, including superior longitudinal fasciculus, frontal aslant, and uncinate fasciculus. These results have strong implications for updated neurobiological models of language, and emphasize a core, language-mediated social disorder in patients with bvFTD.

中文翻译：

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不仅仅是文字：外侧神经解剖网络支持行为变异额颞叶痴呆中的间接言语行为理解和话语

间接言语行为——对询问时间的人回答“我今天忘记戴手表”——在日常对话中无处不在，但在当前的语言神经生物学模型中却没有得到充分研究。要理解这样的间接言语行为，听者不仅要解码话语的词汇语义内容，还要做出语用的、桥接的推理。这种推断允许听者推导出说话者的真实意图——例如，在上述对话中，说话者无法提供时间。在目前的工作中，我们通过询问患有行为变异性额颞叶痴呆（bvFTD，n = 21）的非失语症患者和患有遗忘型轻度认知障碍（MCI，n = 17）的脑损伤对照来判断简单的问题来解决这一主要差距：形式的回答对话框：“你想要一些蛋糕作为甜点吗？” “我现在的饮食非常严格，”并将结果与​​结构和扩散 MRI 相关联。准确性和反应时间结果表明，与直接言语行为理解相比，患有 bvFTD 而非 MCI 的受试者在间接方面有选择性地受损，部分原因是他们的社交和执行限制，并且表现与护理人员对沟通效率的判断有关。MRI 成像将观察到的 bvFTD 损伤与皮层变薄联系起来，不仅在传统的语言相关区域，而且在涉及社会和执行大脑网络的额顶叶区域。最后，弥散张量成像分析涉及背侧和腹侧投射流中的白质束，包括上纵束、额斜束和钩状束。