Vita-Salute San Raffaele University, Milan, Italy.
Brain Topogr. 2010 Jan;22(4):318-32. doi: 10.1007/s10548-009-0126-1. Epub 2009 Dec 12.
There is evidence that the human prefrontal cortex is asymmetrically involved in long-term episodic memory processing. Moreover, abstract and concrete words processing has been reported to differentially involve prefrontal and parietal areas. We implemented a two-stages functional magnetic resonance imaging (fMRI)-repetitive transcranial magnetic stimulation (rTMS) paradigm to investigate the role of the dorsolateral prefrontal cortices (DLPFCs) and parietal cortices (PARCs) in encoding and retrieval of abstract and concrete words. Using this paradigm we could select areas to be stimulated on the basis of single-subject (SS) anatomical and functional data, investigating the usefulness of this integration approach. With respect to fMRI, abstract and concrete words differed only for a greater left fusiform gyrus activation for concrete words. In turn, significant rTMS effects were found, but only for the retrieval of abstract words. Consistent with previous findings, repetitive stimulation of the right DLPFC had a specific impact on episodic retrieval. Memory retrieval performance was also disrupted when rTMS was applied to the left PARC. Finally, we found a significant positive correlation between the effect sizes of SS right PARC activations for abstract word retrieval and the consequent rTMS interference effects. Taken together these data provide for the first time evidence that also the PARC has a necessary role in episodic retrieval of abstract words. Importantly, from a methodological perspective, our data demonstrate that fMRI-guided rTMS with a SS approach provides a powerful tool to investigate the neural underpinnings of cognitive functions.
有证据表明，人类前额叶皮层在长期情景记忆处理中存在不对称性。此外，已有研究报道，抽象词和具体词的处理会分别涉及前额叶和顶叶区域。我们实施了一个两阶段的功能磁共振成像（fMRI）-重复经颅磁刺激（rTMS）范式，以研究背外侧前额叶皮层（DLPFCs）和顶叶皮层（PARCs）在编码和提取抽象词和具体词中的作用。使用这种范式，我们可以根据单个受试者（SS）的解剖学和功能数据选择要刺激的区域，从而研究这种整合方法的有效性。在 fMRI 方面，抽象词和具体词的唯一区别在于，具体词会引起左梭状回更大的激活。反过来，我们发现了显著的 rTMS 效应，但仅针对抽象词的提取。与先前的发现一致，对右侧 DLPFC 的重复刺激对情景记忆提取有特定影响。当 rTMS 施加于左侧 PARC 时，记忆提取性能也会受到干扰。最后，我们发现 SS 右侧 PARC 在提取抽象词时的激活效应大小与随后的 rTMS 干扰效应之间存在显著的正相关。综上所述，这些数据首次提供了证据表明，PARC 在提取抽象词的情景记忆中也具有必要的作用。重要的是，从方法论的角度来看，我们的数据表明，基于 SS 方法的 fMRI 引导 rTMS 提供了一种强大的工具来研究认知功能的神经基础。
