Mummery C J, Patterson K, Wise R J, Vandenberghe R, Price C J, Hodges J R
Wellcome Department of Cognitive Neurology, Institute of Neurology, London, UK.
Brain. 1999 Jan;122 ( Pt 1):61-73. doi: 10.1093/brain/122.1.61.
Semantic dementia refers to the variant of frontotemporal dementia in which there is progressive semantic deterioration and anomia in the face of relative preservation of other language and cognitive functions. Structural imaging and SPECT studies of such patients have suggested that the site of damage, and by inference the region critical to semantic processing, is the anterolateral temporal lobe, especially on the left. Recent functional imaging studies of normal participants have revealed a network of areas involved in semantic tasks. The present study used PET to examine the consequences of focal damage to the anterolateral temporal cortex for the operation of this semantic network. We measured PET activation associated with a semantic decision task relative to a visual decision task in four patients with semantic dementia compared with six age-matched normal controls. Normals activated a network of regions consistent with previous studies. The patients activated some areas consistently with the normals, including some regions of significant atrophy, but showed substantially reduced activity particularly in the left posterior inferior temporal gyrus (iTG) (Brodmann area 37/19). Voxel-based morphometry, used to identify the regions of structural deficit, revealed significant anterolateral temporal atrophy (especially on the left), but no significant structural damage to the posterior inferior temporal lobe. Other evidence suggests that the left posterior iTG is critically involved in lexical-phonological retrieval: the lack of activation here is consistent with the observation that these patients are all anomic. We conclude that changes in activity in regions distant from the patients' structural damage support the argument that their prominent anomia is due to disrupted temporal lobe connections.
语义性痴呆是额颞叶痴呆的一种变体，其特征是在其他语言和认知功能相对保留的情况下，语义进行性衰退和命名障碍。对此类患者的结构成像和单光子发射计算机断层扫描（SPECT）研究表明，损伤部位（由此推断对语义加工至关重要的区域）是颞叶前外侧，尤其是左侧。最近对正常受试者的功能成像研究揭示了一个参与语义任务的脑区网络。本研究使用正电子发射断层扫描（PET）来检查颞叶前外侧皮质局灶性损伤对这个语义网络运作的影响。我们测量了4名语义性痴呆患者与6名年龄匹配的正常对照者在语义决策任务相对于视觉决策任务时的PET激活情况。正常受试者激活了与先前研究一致的脑区网络。患者激活了一些与正常受试者一致的区域，包括一些明显萎缩的区域，但活动明显减少，尤其是在左侧颞下回后部（Brodmann 37/19区）。基于体素的形态测量学用于识别结构缺损区域，结果显示颞叶前外侧显著萎缩（尤其是左侧），但颞下回后部无明显结构损伤。其他证据表明，左侧颞下回后部在词汇 - 语音检索中起关键作用：此处缺乏激活与这些患者均存在命名障碍的观察结果一致。我们得出结论，远离患者结构损伤区域的活动变化支持了以下观点，即他们明显的命名障碍是由于颞叶连接中断所致。
