1 Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo 153-8902, Japan.
Brain. 2014 Apr;137(Pt 4):1193-212. doi: 10.1093/brain/awu013. Epub 2014 Feb 11.
The opercular/triangular parts of the left inferior frontal gyrus and the left lateral premotor cortex are critical in syntactic processing. We have recently indicated that a glioma in one of these regions is sufficient to cause agrammatic comprehension. In the present study, we aimed to show how normally existing syntax-related networks are functionally reorganized by a lesion. Twenty-one patients with a left frontal glioma preoperatively performed a picture-sentence matching task, and underwent functional magnetic resonance imaging scans in an event-related design. We established two qualitatively different types of agrammatic comprehension, depending on glioma location. Patients with a glioma in the left lateral premotor cortex had a more profound deficit in the comprehension of scrambled sentences than that of active and passive sentences. In contrast, patients with a glioma in the opercular/triangular parts of the left inferior frontal gyrus had a more profound deficit in the comprehension of passive and scrambled sentences than that of active sentences. Moreover, we found dramatic changes in the activation patterns in these two patient groups, which accompanied abnormal overactivity and/or underactivity in the syntax-related regions. Furthermore, by examining functional connectivity in the normal brain, we identified three syntax-related networks among those regions, and anatomically visualized connections within individual networks by using diffusion tensor imaging. The first network consists of the opercular/triangular parts of the left inferior frontal gyrus, left intraparietal sulcus, right frontal regions, presupplementary motor area, and right temporal regions. These regions were overactivated in the patients with a glioma in the left lateral premotor cortex only for correct responses, indicating a cognitive change. The second network consists of the left lateral premotor cortex, left angular gyrus, lingual gyrus, and cerebellar nuclei. These regions were overactivated in the patients with a glioma in the opercular/triangular parts of the left inferior frontal gyrus for both correct and incorrect responses, indicating a neuronal change. The third network consists of the left ventral frontal and posterior temporal regions. These regions were underactivated in the patients with a glioma in the opercular/triangular parts of the left inferior frontal gyrus, indicating another neuronal change. These results demonstrate that agrammatic comprehension is associated with the global reorganization of functionally distinct networks, which indeed reflects a differential change in the relative contribution of these three networks to normal syntax-related functions.
左侧额下回的脑岛/三角部和左侧外侧运动前皮质对于句法处理至关重要。我们最近发现，这些区域中的一个胶质瘤足以导致语法缺失性理解障碍。在本研究中，我们旨在展示病变如何导致与句法相关的网络功能重组。21 名术前患有左侧额部胶质瘤的患者进行了图片-句子匹配任务，并在事件相关设计中进行了功能磁共振成像扫描。我们根据肿瘤位置确定了两种不同类型的语法缺失性理解障碍。肿瘤位于左侧外侧运动前皮质的患者在理解错乱句方面的缺陷比主动句和被动句更为严重。相比之下，肿瘤位于左侧额下回脑岛/三角部的患者在理解被动句和错乱句方面的缺陷比主动句更为严重。此外，我们在这两组患者中发现了激活模式的剧烈变化，这些变化伴随着与句法相关区域的异常过度活跃和/或活动不足。此外，通过检查正常大脑的功能连接，我们在这些区域之间确定了三个与语法相关的网络，并通过弥散张量成像对个体网络内的连接进行了解剖可视化。第一个网络由左侧额下回脑岛/三角部、左侧顶内沟、右侧额叶区域、辅助运动区和右侧颞叶区域组成。肿瘤位于左侧外侧运动前皮质的患者仅在正确反应时，这些区域过度活跃，表明认知发生了变化。第二个网络由左侧外侧运动前皮质、左侧角回、舌回和小脑核组成。肿瘤位于左侧额下回脑岛/三角部的患者在正确和错误反应时，这些区域均过度活跃，表明神经元发生了变化。第三个网络由左侧腹侧额叶和后颞叶区域组成。肿瘤位于左侧额下回脑岛/三角部的患者这些区域活动不足，表明神经元发生了另一种变化。这些结果表明，语法缺失性理解障碍与功能上不同的网络的全局重组有关，这确实反映了这三个网络对正常句法相关功能的相对贡献的差异变化。
