Wu Carolyn W-H, van Gelderen Peter, Hanakawa Takashi, Yaseen Zaneb, Cohen Leonardo G
Laboratory of Functional and Molecular Imaging, Human Cortical Physiology Section, NINDS, NIH, Bethesda, MD 20892, USA.
Neuroimage. 2005 Oct 1;27(4):872-84. doi: 10.1016/j.neuroimage.2005.05.055.
Somatosensory stimulation (SS), leading to increases in motor cortical excitability, influences motor performance in patients with brain lesions like stroke. The mechanisms by which SS modulates motor function are incompletely understood. Here, we used functional magnetic resonance imaging (fMRI, blood-oxygenation-level-dependent (BOLD), and perfusion imagings simultaneously acquired in a 3 T magnet) to assess the effects of SS on thumb-movement-related activation in three regions of interest (ROI) in the motor network: primary motor cortex (M1), primary somatosensory cortex (S1), and dorsal premotor cortex (PMd) in healthy volunteers. Scans were obtained in different sessions before and after 2-h electrical stimulation applied to the median nerve at the wrist (MNS), to the skin overlying the shoulder deltoid muscle (DMS), and in the absence of stimulation (NOSTIM) in a counterbalanced design. We found that baseline perfusion intensity was comparable within and across sessions. MNS but not DMS nor NOSTIM led to an increase in signal intensity and number of voxels activated by performance of median nerve-innervated thumb movements in M1, S1, and PMd for up to 60 min. Task-related fMRI activation changes were most prominent in M1 followed by S1 and to a lesser extent in PMd. MNS elicited a displacement of the center of gravity for the thumb movement representation towards the other finger representations within S1. These results indicate that MNS leads to an expansion of the thumb representation towards other finger representations within S1, a form of plasticity that may underlie the influence of SS on motor cortical function, possibly supporting beneficial effects on motor control.
体感刺激（SS）可导致运动皮质兴奋性增加，影响中风等脑损伤患者的运动表现。SS调节运动功能的机制尚未完全明确。在此，我们使用功能磁共振成像（fMRI，在3T磁体中同时采集血氧水平依赖（BOLD）和灌注成像）来评估SS对健康志愿者运动网络中三个感兴趣区域（ROI）与拇指运动相关激活的影响，这三个区域分别为初级运动皮质（M1）、初级体感皮质（S1）和背侧运动前皮质（PMd）。扫描在不同阶段进行，采用平衡设计，分别在腕部正中神经（MNS）、肩部三角肌上方皮肤（DMS）接受2小时电刺激之前和之后，以及无刺激（NOSTIM）的情况下进行。我们发现，各阶段内及各阶段间的基线灌注强度相当。MNS而非DMS或NOSTIM可导致M1、S1和PMd中由正中神经支配的拇指运动激活的信号强度和体素数量增加，持续长达60分钟。任务相关的fMRI激活变化在M1中最为显著，其次是S1，在PMd中程度较轻。MNS引起了S1内拇指运动表征重心向其他手指表征的位移。这些结果表明，MNS导致S1内拇指表征向其他手指表征扩展，这是一种可塑性形式，可能是SS对运动皮质功能产生影响的基础，可能支持对运动控制的有益作用。
