Centre for Functional and Metabolic Mapping, Robarts Research Institute, The University of Western Ontario, London, Ontario, Canada.
Department of Medical Biophysics, The University of Western Ontario, London, Ontario, Canada.
J Neurophysiol. 2020 Dec 1;124(6):1900-1913. doi: 10.1152/jn.00480.2020. Epub 2020 Oct 28.
The common marmoset () 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 postmortem analyses. Here, we demonstrate the feasibility for getting high-quality and reproducible 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, and 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. At the subcortical level, 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 noninvasive way in awake marmosets. We used somatosensory stimulation combined with functional MRI (fMRI) in awake marmosets to reveal the topographic body representation in areas S1, S2, thalamus, and putamen. We showed the existence of a body representation organization within the thalamus and the cingulate cortex by computing functional connectivity maps from seeds defined in S1/S2, using resting-state fMRI data. This noninvasive approach will be essential for chronic studies by guiding invasive recording and manipulation techniques.
普通狨猴（Callithrix jacchus）是一种小型新世界灵长类动物，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，但所有结果都来自于使用侵入性技术和死后分析的麻醉动物。在这里，我们展示了在清醒的狨猴中使用功能磁共振成像（fMRI）获得高质量和可重复的体感映射的可行性。我们在四只动物身上获取了 fMRI 序列，同时它们接受了来自面部、手臂或腿部的空气喷刺激。我们发现了一个具有腿部代表区域最内侧、面部代表区域最外侧以及手臂代表区域在 3a、3b 和 1/2 区域之间的身体代表区域的地形。在 S2 和 PV 中，从尾侧向吻侧识别到从腿部到面部的类似序列。通过生成在初级和次级体感区域中定义的种子的功能连接图，我们在后扣带和中扣带皮层内鉴定出两个触觉代表区域。然而，与人类和猕猴不同，没有观察到明显的体感图谱。在皮质下水平，我们在丘脑和纹状体中发现了身体代表区域，这是在狨猴中首次发现。这些图谱具有相似的组织，与旧世界猕猴和人类以前发现的图谱相似，这表明这些皮质下的体感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第一次全脑体感反应映射。我们在清醒的狨猴中使用体感刺激结合功能磁共振成像（fMRI）来揭示 S1、S2、丘脑和纹状体中的身体代表区域的地形。通过使用静息态 fMRI 数据从 S1/S2 中定义的种子计算功能连接图，我们展示了在丘脑和扣带皮层内存在身体代表区域的组织。这种非侵入性方法将通过指导侵入性记录和操作技术，对于慢性研究至关重要。
