CNRS (CERCO) UMR Unité 5549, Université Paul Sabatier, Toulouse, 31059, France.
Pôle NeuroSciences (Neurochirurgie), Centres Hospitalo-Universitaires, Toulouse, 31059, France.
J Physiol. 2018 Mar 1;596(5):941-956. doi: 10.1113/JP275243. Epub 2018 Jan 19.
We performed a prospective electrostimulation study, based on 50 operated intact patients, to acquire accurate MNI coordinates of the functional areas of the somatosensory homunculus. In the contralateral BA1, the hand representation displayed not only medial-to-lateral, little-finger-to-thumb, but also rostral-to-caudal discrete somatotopy, with the tip of each finger located more caudally than the proximal phalanx. The analysis of the MNI body coordinates showed rare inter-individual variations in the medial-to-lateral somatotopic organization in these patients with rather different intensity thresholds needed to elicit sensations in different body parts. We found some similarities but also substantial differences with the previous, seminal works of Penfield and his colleagues. We propose a new drawing of the human somatosensory homunculus according to MNI space.
In this prospective electrostimulation study, based on 50 operated patients with no sensory deficit and no brain lesion in the postcentral gyrus, we acquired coordinates in the standard MNI space of the functional areas of the somatosensory homunculus. The 3D brain volume of each patient was normalized to that space to obtain the MNI coordinates of the stimulation site locations. For 647 sites stimulated on Brodmann Area 1 (and 1025 in gyri nearby), 258 positive points for somatosensory response (40%) were found in the postcentral gyrus. In the contralateral BA1, the hand representation displayed not only medial-to-lateral and little-finger-to-thumb somatotopy, but also rostral-to-caudal discrete somatotopy, with the tip of each finger located more caudally than the proximal phalanx. We detected a medial-to-lateral, tip-to-base tongue organization but no rostral-to-caudal functional organization. The analysis of the MNI body coordinates showed rare inter-individual variations in the medial-to-lateral somatotopic organization in these patients with intact somatosensory cortex. Positive stimulations were detected through the 'on/off' outbreak effect and discriminative touch sensations were the sensations reported almost exclusively by all patients during stimulation. Mean hand (2.39 mA) and tongue (2.60 mA) positive intensity thresholds were lower (P < 0.05) than the intensities required to elicit sensations in the other parts of the body. Unlike the previous, seminal works of Penfield and colleagues, we detected no sensations such as sense of movement or desire to move, no somatosensory responses outside the postcentral gyrus, and no bilateral responses for face/tongue stimulations. We propose a rationalization of the standard drawing of the somatosensory homunculus according to MNI space.
我们对 50 例完整手术患者进行了前瞻性电刺激研究，以获得躯体感觉同态功能区的准确 MNI 坐标。在对侧 BA1 中，手部代表区域不仅显示了从内侧到外侧、从小指到拇指的连续体节排列，而且还显示了从近到远的离散体节排列，每个手指的指尖比近节指骨更靠后。对 MNI 身体坐标的分析表明，这些患者的躯体感觉组织在从内侧到外侧的方向上存在罕见的个体间变异，而不同身体部位产生感觉所需的强度阈值差异较大。我们发现了与彭菲尔德及其同事之前的开创性工作的一些相似之处，但也有很大的不同。根据 MNI 空间，我们提出了一种新的人类躯体感觉同态图。
在这项前瞻性电刺激研究中，我们对 50 例无感觉缺失且后中央回无脑损伤的手术患者进行了研究，获得了躯体感觉同态功能区的标准 MNI 坐标。每位患者的 3D 脑体积都被归一化为该空间，以获得刺激部位的 MNI 坐标。在 Brodmann 区 1（BA1）的 647 个刺激点（1025 个在附近的脑回）中，258 个（40%）刺激点出现了躯体感觉反应阳性。在对侧 BA1 中，手部代表区域不仅显示了从内侧到外侧、从小指到拇指的连续体节排列，而且还显示了从近到远的离散体节排列，每个手指的指尖比近节指骨更靠后。我们检测到了舌部从舌尖到舌根的连续体节排列，但没有从近到远的功能组织。对 MNI 身体坐标的分析表明，这些感觉皮层完整的患者在从内侧到外侧的躯体感觉组织方面存在罕见的个体间变异。通过“开/关”爆发效应检测到阳性刺激，所有患者在刺激过程中几乎都报告了辨别性触觉感觉。手部（2.39 mA）和舌部（2.60 mA）的阳性刺激强度阈值均低于（P < 0.05）身体其他部位产生感觉所需的强度阈值。与彭菲尔德及其同事之前的开创性工作不同，我们没有检测到运动感觉或运动欲望等感觉，没有在后中央回以外的部位产生躯体感觉反应，也没有对面部/舌部刺激产生双侧反应。我们根据 MNI 空间对躯体感觉同态图进行了合理化。
