Lesion and imaging studies have shown that the left inferior frontal gyrus (IFG) is involved in selective semantic retrieval of information from the temporal lobes. However, causal, i.e., interventional, evidence is sparse. In the present study we addressed this question by testing whether transcranial direct current stimulation (tDCS) over the left IFG in a group of individuals with primary progressive aphasia may improve semantic fluency, a task that relies to selective semantic retrieval. Semantic fluency improved significantly more in the tDCS vs. sham condition immediately post-treatment and improvement lasted up to 2 months. We further addressed the question of who will benefit most from such an intervention by testing possible demographic, clinical and functional connectivity variables that may predict the behavioral tDCS effect. We found that patients with stronger baseline functional connectivity between the subareas of the left IFG opercularis and triangularis, and between the middle temporal pole and superior temporal gyrus. were the most likely to benefit from tDCS over the left IFG. We thus provided causal evidence that the left IFG is the neural substrate of selective semantic retrieval and tDCS over the left IFG may improve semantic fluency in individuals with stronger baseline functional connectivity.

中文翻译：

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左下额回有因果关系涉及选择性语义检索：来自tDCS的原发性进行性失语症的证据

病变和影像学研究表明，左下额回（IFG）参与了颞叶信息的选择性语义检索。但是，因果关系（即介入性）证据很少。在本研究中，我们通过测试一组原发性进行性失语症患者的左IFG上的经颅直流电刺激（tDCS）是否可以改善语义流利性，这项工作依赖于选择性语义检索。与假手术后相比，tDCS中的语义流畅性有了显着提高，并且改善持续了2个月。我们通过测试可能预测行为tDCS效果的可能的人口统计，临床和功能连接性变量，进一步解决了谁将从此类干预中受益最大的问题。我们发现，左IFG opercularis的子区域和三角形的子区域之间，颞中极和颞上回之间的基线功能连接性较强的患者。是最有可能从左IFG受益于tDCS的。因此，我们提供了因果证据，即左IFG是选择性语义检索的神经基础，而在左IFG上的tDCS可能会改善具有较强基线功能连接性的个体的语义流畅性。