The role of the posterior cerebellum in social cognition is well established; however, it is still unclear whether different cerebellar subregions contribute to different social cognitive processes by exerting specific functions. Here, we employed transcranial magnetic stimulation (TMS) in male and female healthy humans to test the hypothesis of the existence of a medial-to-lateral gradient in the functional organization of the posterior cerebellum, according to which the phylogenetically newer cerebellar hemispheres are involved in tasks requiring higher-level social inferences whereas vermal/medial sectors are involved in basic perceptual emotional mechanisms. We found that interfering via TMS with activity of the medial cerebellum significantly impaired basic emotional recognition/discrimination. In turn, only TMS over the lateral cerebellum affected a task requiring recognizing an emotion considering the social context in which it was experienced. Overall, our data support the existence of a medial-to-lateral gradient in the posterior cerebellum, with medial sectors supporting basic emotion recognition and lateral sectors being recruited when the task taps on higher inferential processing/mentalizing. Interestingly, the contribution of the cerebellum in these different processes seems to be restricted to negative emotional stimuli.

SIGNIFICANCE STATEMENT The cerebellum has been recently recognized as a critical component of the social brain, however, the functional topography of this structure in relation to social and emotional processes is still debated. By adopting a causative approach through the use of transcranial magnetic stimulation (TMS), the present study critically insights into the functional organization of the posterior cerebellum by testing the hypothesis of a medial-to-lateral gradient that reflects increasing complexity of social cognitive processes. Our findings demonstrate that lateral and medial cerebellar regions exert partially distinguishable functions in the social cognitive domain, with the medial cerebellum that mainly mediates basic perceptual emotional mechanisms while the lateral cerebellum, although supporting more basic functions, further subserves higher-level social operations.

小脑后部在社会认知中的作用已得到充分证实。然而，目前尚不清楚不同的小脑亚区域是否通过发挥特定功能来促进不同的社会认知过程。在这里，我们在男性和女性健康人群中采用经颅磁刺激（TMS）来测试后小脑功能组织中存在内侧到外侧梯度的假设，根据该梯度，系统发育较新的小脑半球也参与其中在需要更高层次的社会推理的任务中，而外侧/内侧部分涉及基本的感知情感机制。我们发现，通过 TMS 干扰内侧小脑的活动会显着损害基本的情绪识别/辨别能力。反过来，只有小脑外侧的 TMS 会影响需要识别情绪的任务，考虑到情绪所经历的社会背景。总的来说，我们的数据支持小脑后部存在从内侧到外侧的梯度，内侧区域支持基本的情绪识别，而当任务需要更高的推理处理/心智化时，外侧区域就会被招募。有趣的是，小脑在这些不同过程中的贡献似乎仅限于负面情绪刺激。

意义声明小脑最近被认为是社会大脑的重要组成部分，然而，这种结构与社会和情感过程相关的功能拓扑仍然存在争议。通过使用经颅磁刺激（TMS）采用因果方法，本研究通过测试反映社会认知过程复杂性不断增加的内侧到外侧梯度的假设，批判性地洞察了小脑后部的功能组织。我们的研究结果表明，小脑外侧区域和小脑内侧区域在社会认知领域发挥部分可区分的功能，小脑内侧区域主要介导基本的感知情感机制，而小脑外侧区域虽然支持更基本的功能，但进一步促进更高层次的社会运作。