Laughter is a complex motor behavior occurring in both emotional and nonemotional contexts. Here, we investigated whether the different functions of laughter are mediated by distinct networks and, if this is the case, which are the white matter tracts sustaining them. We performed a multifiber tractography investigation placing seeds in regions involved in laughter production, as identified by previous intracerebral electrical stimulation studies in humans: the pregenual anterior cingulate (pACC), ventral temporal pole (TPv), frontal operculum (FO), presupplementary motor cortex, and ventral striatum/nucleus accumbens (VS/NAcc). The primary motor cortex (M1) and two subcortical territories were also studied to trace the descending projections. Results provided evidence for the existence of two relatively distinct networks. A first network, including pACC, TPv, and VS/NAcc, is interconnected through the anterior cingulate bundle, the accumbofrontal tract, and the uncinate fasciculus, reaching the brainstem throughout the mamillo-tegmental tract. This network is likely involved in the production of emotional laughter. A second network, anchored to FO and M1, projects to the brainstem motor nuclei through the internal capsule. It is most likely the neural basis of nonemotional and conversational laughter. The two networks interact throughout the pre-SMA that is connected to both pACC and FO.

中文翻译：

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两个用于笑的神经网络：牵引研究。

笑是一种复杂的运动行为，发生在情绪和非情绪环境中。在这里，我们调查了笑的不同功能是否由不同的网络介导，如果是这样，哪些是维持它们的白质束。我们进行了一项多纤维纤维束成像研究，将种子放置在与笑声产生有关的区域，正如之前对人类的脑内电刺激研究所确定的那样：前扣带回 (pACC)、腹侧颞极 (TPv)、额叶盖 (FO)、前补充运动皮层和腹侧纹状体/伏隔核 (VS/NAcc)。还研究了初级运动皮层 (M1) 和两个皮层下区域以追踪下降的投影。结果为存在两个相对不同的网络提供了证据。第一个网络，包括 pACC、TPv 和 VS/NAcc，通过前扣带束、伏前束和钩束相互连接，到达整个乳头-被盖束的脑干。这个网络很可能与情绪化笑声的产生有关。第二个网络，锚定到 FO 和 M1，通过内囊投射到脑干运动核。它很可能是非情绪化和对话式笑声的神经基础。这两个网络在连接到 pACC 和 FO 的 pre-SMA 中进行交互。锚定于 FO 和 M1，通过内囊投射到脑干运动核。它很可能是非情绪化和对话式笑声的神经基础。这两个网络在连接到 pACC 和 FO 的 pre-SMA 中进行交互。锚定于 FO 和 M1，通过内囊投射到脑干运动核。它很可能是非情绪化和对话式笑声的神经基础。这两个网络在连接到 pACC 和 FO 的 pre-SMA 中进行交互。