The common marmoset (Callithrix jacchus) is a small-bodied New World primate that is becoming an important model to study brain functions. Despite several studies exploring the somatosensory system of marmosets, all results have come from anesthetized animals using invasive techniques and post-mortem analyses. Here we demonstrate the feasibility for getting high-quality and reproduceable somatosensory mapping in awake marmosets with functional magnetic resonance imaging (fMRI). We acquired fMRI sequences in four animals while they received tactile stimulation (via air-puffs), delivered to the face, arm or leg. We found a topographic body representation with the leg representation in the most medial part, the face representation in the most lateral part, and the arm representation between leg and face representation within areas 3a, 3b, 1/2. A similar sequence from leg to face from caudal to rostral sites was identified in areas S2 and PV. By generating functional connectivity maps of seeds defined in the primary and second somatosensory regions, we identified two clusters of tactile representation within the posterior and midcingulate cortex. However, unlike humans and macaques, no clear somatotopic maps were observed. We found a somatotopic body representation in the thalamus and, for the first time in marmosets, in the putamen. These maps have similar organizations as those previously found in Old World macaque monkeys and humans, suggesting that these subcortical somatotopic organizations were already established before Old and New World primates diverged. Our results show the first whole brain mapping of somatosensory responses acquired in a non-invasive way in awake marmosets.

中文翻译：

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用超高场 fMRI 研究清醒狨猴体感反应的全脑图谱

普通狨猴（Callithrix jacchus）是一种体型较小的新世界灵长类动物，正在成为研究大脑功能的重要模型。尽管有几项研究探索了狨猴的体感系统，但所有结果都来自使用侵入性技术和尸检分析的麻醉动物。在这里，我们证明了通过功能磁共振成像 (fMRI) 在清醒的狨猴中获得高质量和可复制的体感测绘的可行性。我们在四只动物身上获得了 fMRI 序列，同时它们接受了触觉刺激（通过吹气），传递到面部、手臂或腿部。我们发现了一个地形身体表示，其中腿部表示在最内侧，面部表示在最外侧，以及在区域 3a、3b、1/2 内腿部和面部表示之间的手臂表示。在区域 S2 和 PV 中发现了从腿到脸从尾部到嘴部的类似序列。通过生成定义在初级和次级体感区域的种子的功能连接图，我们在后皮层和中扣带回皮层中确定了两个触觉表征集群。然而，与人类和猕猴不同，没有观察到清晰的体位图。我们在丘脑和狨猴的壳核中首次发现了体细胞体表征。这些地图具有与之前在旧世界猕猴和人类中发现的相似的组织，表明这些皮层下体表组织在旧世界和新世界灵长类动物分化之前就已经建立。我们的结果显示了在清醒的狨猴中以非侵入性方式获得的体感反应的第一个全脑映射。