Cognitive Neurology & Alzheimer's Disease Center, Northwestern University, Chicago, IL 60611, USA; Department of Neurology, Northwestern University, Chicago, IL 60611, USA; Department of Psychology, Cleveland State University, Cleveland, OH 44115, USA.
Cognitive Neurology & Alzheimer's Disease Center, Northwestern University, Chicago, IL 60611, USA; Department of Neurology, Northwestern University, Chicago, IL 60611, USA.
Neuropsychologia. 2018 Aug;117:92-101. doi: 10.1016/j.neuropsychologia.2018.05.019. Epub 2018 May 23.
The semantic variant of primary progressive aphasia (PPA-S) is diagnosed based on impaired single-word comprehension, but nonverbal impairments in face and object recognition can also be present, particularly in later disease stages. PPA-S is associated with focal atrophy in the left anterior temporal lobe (ATL), often accompanied by a lesser degree of atrophy in the right ATL. According to a dual-route account, the left ATL is critical for verbal access to conceptual knowledge while nonverbal access to conceptual knowledge depends upon the integrity of right ATL. Consistent with this view, single-word comprehension deficits in PPA-S have consistently been linked to the degree of atrophy in left ATL. In the current study we examined object processing and cortical thickness in 19 patients diagnosed with PPA-S, to evaluate the hypothesis that nonverbal object impairments would instead be determined by the amount of atrophy in the right ATL. All patients demonstrated inability to access conceptual knowledge on standardized tests with word stimuli: they were unable to match spoken words with their corresponding pictures on the Peabody Picture Vocabulary Test. Only a minority of patients, however, performed abnormally on an experimental thematic verification task, which requires judgments as to whether pairs of object pictures are thematically-associated, and does not rely on auditory or visual word input. The entire PPA-S group showed cortical thinning in left ATL, but atrophy in right ATL was more prominent in the subgroup with low verification scores. Thematic verification scores were correlated with cortical thickness in the right rather than left ATL, an asymmetric mapping which persisted when controlling for the degree of atrophy in the contralateral hemisphere. These results are consistent with a dual-route account of conceptual knowledge: breakdown of the verbal left hemispheric route produces an aphasic syndrome, which is only accompanied by visual object processing impairments when the nonverbal right hemispheric route is also compromised.
原发性进行性失语（PPA）的语义变体基于单字理解受损而诊断，但在后期疾病阶段也可能存在面孔和物体识别的非言语障碍。PPA-S 与左侧前颞叶（ATL）的局灶性萎缩相关，通常伴有右侧 ATL 较小程度的萎缩。根据双路径假说，左侧 ATL 对言语访问概念知识至关重要，而非言语访问概念知识则取决于右侧 ATL 的完整性。与该观点一致，PPA-S 的单字理解缺陷与左侧 ATL 的萎缩程度一致。在当前的研究中，我们检查了 19 名被诊断为 PPA-S 的患者的物体处理和皮质厚度，以评估以下假设：非言语物体障碍将由右侧 ATL 的萎缩程度决定。所有患者在使用单词刺激的标准化测试中都无法访问概念知识：他们无法将口语单词与 Peabody 图片词汇测试中的相应图片匹配。然而，只有少数患者在实验主题验证任务中表现异常，该任务需要判断两个物体图片是否主题相关，并且不依赖于听觉或视觉单词输入。整个 PPA-S 组在左侧 ATL 中表现出皮质变薄，但在验证得分较低的亚组中，右侧 ATL 的萎缩更为明显。主题验证得分与右侧而不是左侧 ATL 的皮质厚度相关，当控制对侧半球的萎缩程度时，这种不对称映射仍然存在。这些结果与概念知识的双路径假说一致：言语左半球通路的破裂产生失语症综合征，只有当非言语右半球通路也受损时，才会伴有视觉物体处理障碍。
