Obesity is a major concern inmany societies for its impact on individual health and societal costs [1]. Therapeutic options however are still limited with respect to efficacy and applicability. Food impulsivity and hyperphagia play a key role in obesity [2] and are associatedwith alterations of the activity of several brain structures of the reward system, including orbitofrontal cortex (OFC) and ventromedial prefrontal cortex (vmPFC), insula, anterior cingulate cortex (ACC), and dopaminergic (DA) midbrain structures (e.g., [3,4]). Functional alterations of these brain areas are involved in reward processing-related disorders, including eating disorders (e.g., [5]). Noninvasive brain stimulation provides an innovative tool for treating hyperphagia with the advantage of modulating neural activity in absence of surgical and/or pharmacological interventions, which have often limited applicability due to obesity-associated health complications. Dorsolateral prefrontal cortex is the typical cortical target for treating eating disorders, given its key role in up-/downregulation of the reward circuitry [6] and inhibitory control functions [7].Most studies in the field describe short-term improvements [8,9]. However, no studies tackling alternative cortical targets more specifically associated with the reward circuit are currently available. Here, we tested whether downregulation of the tongue musclerepresenting area of the primary motor cortex (tnM1) via transcranial direct current stimulation (tDCS) e a plasticity-inducing noninvasive brain stimulation tool reduces hunger in healthy humans. This research hypothesis originates from the evidence that tnM1 is directly connected with key regions of the reward system [10], including OFC, ACC, insula, ventral putamen, caudate nucleus and the amygdala. On the other hand, limb regions of the motor cortex do not project to OFC or insular regions. Remarkably, we have documented that tnM1 excitability is modulated by nicotine craving [11], distaste [12], andmoral disgust [13], which supports a functional link between tnM1 and reward-relevant processes in humans. We applied 1 mA tDCS for 15 minutes over the tnM1 in twentyfour food-deprived (fasting for 6h) healthy humans (mean age 29, standard deviation 5.56, 15 females). Participants were recruited by the Leibniz Research Centre for Working Environment and Human Factors (IfADo) by online advertisements, and compensated with 10 euros/h for their time spent and travel expenses. They provided written informed consent and procedures were approved by the local ethics committee. Participants were excluded from the study if they met any of the following criteria: intake of psychoactive medication, presence of a metal object/implant in their brain, skull, scalp, or neck, implantable devices (e.g. cardiac pacemaker),

中文翻译：

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舌运动皮层上的经颅直流电刺激可降低健康人的食欲

肥胖对个人健康和社会成本的影响是许多社会关注的主要问题[1]。然而，治疗选择在功效和适用性方面仍然有限。食物冲动和食欲过盛在肥胖中起着关键作用 [2] 并且与奖赏系统的几种大脑结构的活动改变有关，包括眶额皮层 (OFC) 和腹内侧前额叶皮层 (vmPFC)、脑岛、前扣带皮层 (ACC) ) 和多巴胺能 (DA) 中脑结构（例如，[3,4]）。这些大脑区域的功能改变与奖赏处理相关的障碍有关，包括进食障碍（例如，[5]）。无创脑刺激提供了一种治疗食欲亢进的创新工具，其优势是在没有手术和/或药物干预的情况下调节神经活动，由于肥胖相关的健康并发症，这些干预的适用性通常有限。背外侧前额叶皮层是治疗饮食失调的典型皮层目标，因为它在奖励回路 [6] 和抑制控制功能的上调/下调中发挥关键作用 [7]。该领域的大多数研究都描述了短期改善 [8, 9]。然而，目前还没有针对与奖励回路更具体相关的替代皮层目标的研究。这里，我们测试了通过经颅直流电刺激 (tDCS) 和可塑性诱导的非侵入性脑刺激工具对初级运动皮层 (tnM1) 的舌头肌肉代表区域的下调是否会减少健康人的饥饿感。这一研究假设源于tnM1与奖赏系统关键区域直接相关的证据[10]，包括OFC、ACC、岛叶、腹侧壳核、尾状核和杏仁核。另一方面，运动皮层的肢体区域不会投射到 OFC 或岛区。值得注意的是，我们已经证明 tnM1 兴奋性受尼古丁渴望 [11]、厌恶 [12] 和道德厌恶 [13] 的调节，这支持 tnM1 与人类奖励相关过程之间的功能联系。我们在 24 名缺乏食物（禁食 6 小时）的健康人（平均年龄 29 岁，标准差 5.56，15 名女性）的 tnM1 上应用 1 mA tDCS 15 分钟。莱布尼茨工作环境和人为因素研究中心（IfADo）通过在线广告招募参与者，并以每小时 10 欧元的报酬支付他们花费的时间和差旅费。他们提供了书面知情同意书，并且程序得到了当地伦理委员会的批准。如果参与者符合以下任何标准，则他们被排除在研究之外：服用精神药物，大脑、颅骨、头皮或颈部存在金属物体/植入物，可植入设备（例如心脏起搏器），莱布尼茨工作环境和人为因素研究中心（IfADo）通过在线广告招募参与者，并以每小时 10 欧元的报酬支付他们花费的时间和差旅费。他们提供了书面知情同意书，并且程序得到了当地伦理委员会的批准。如果参与者符合以下任何标准，则他们被排除在研究之外：服用精神药物，大脑、颅骨、头皮或颈部存在金属物体/植入物，可植入设备（例如心脏起搏器），莱布尼茨工作环境和人为因素研究中心（IfADo）通过在线广告招募参与者，并以每小时 10 欧元的报酬支付他们花费的时间和差旅费。他们提供了书面知情同意书，并且程序得到了当地伦理委员会的批准。如果参与者符合以下任何标准，则他们被排除在研究之外：服用精神药物，大脑、颅骨、头皮或颈部存在金属物体/植入物，可植入设备（例如心脏起搏器），