Roberts Donna R, Ramsey David, Johnson Kevin, Kola Jejo, Ricci Raffaella, Hicks Christian, Borckardt Jeffrey J, Bloomberg Jacob J, Epstein Charles, George Mark S
Department of Radiology and Radiological Sciences, Medical University of South Carolina, Charleston, SC 29425, USA.
Aviat Space Environ Med. 2010 Jan;81(1):30-40. doi: 10.3357/asem.2532.2009.
Microgravity animal models have demonstrated corticospinal plasticity; however, little is understood of its functional significance. In this pilot study, we explored corticospinal plasticity in a bed rest model. We hypothesized that the lack of weight bearing would induce cortical reorganization correlating with performance.
Four subjects underwent functional MRI (fMRI), transcranial magnetic stimulation (TMS), and functional mobility testing (FMT) before and after 90 d of bed rest. Recruitment curves (RC) were created by measuring motor evoked potentials over a range of TMS intensities with changes in the slope of the RC reflecting changes in corticospinal excitability.
Significant leg RC slope decreases were observed on post-bed rest day 1 (P1) (t(2805) = -4.14, P < 0.0001), P2 (t(2805) = -6.59, P < 0.0001), P3 (t(2805) = -6.15, P < 0.0001), P5 (t(2805) = -7.93, P <0.0001), P8 (t(2805) = -3.30, P = 0.001), and P12 (t(2805)= -3.33, P = 0.0009), suggesting a group decrease in corticospinal excitability in the immediate post-bed rest period with recovery approaching baseline over the following 2 wk. Significant effects were observed for hand RC slopes only for P2 (t(2916) = 1.97, P = 0.049), P3 (t(2916) = -2.12, P = 0.034), and P12 (t(2916) = -2.19, P = 0.029); no significant effects were observed for days P0 (t(2916) = -1.32, ns), P1 (t(2916) = 1.00, ns), P5 (t(2916) = -0.21, ns), or P8 (t(2916) = -0.27, ns). fMRI showed no change in activation for the hand but an increase in activation post-bed rest for the leg. On an individual basis, a more heterogeneous response was found which showed a potential association with performance on FMT.
Results of this research include a better understanding of the cortical plasticity associated with leg disuse and may lead to applications in patient and astronaut rehabilitation.
微重力动物模型已证明皮质脊髓可塑性；然而，对其功能意义了解甚少。在这项初步研究中，我们在卧床休息模型中探索了皮质脊髓可塑性。我们假设缺乏负重会诱导与运动表现相关的皮质重组。
四名受试者在卧床休息90天前后接受了功能磁共振成像（fMRI）、经颅磁刺激（TMS）和功能活动测试（FMT）。通过在一系列TMS强度下测量运动诱发电位来创建募集曲线（RC），RC斜率的变化反映皮质脊髓兴奋性的变化。
在卧床休息后第1天（P1）（t(2805)= -4.14，P < 0.0001）、P2（t(2805)= -6.59，P < 0.0001）、P3（t(2805)= -6.15，P < 0.0001）、P5（t(2805)= -7.93，P <0.0001）、P8（t(2805)= -3.30，P = 0.001）和P12（t(2805)= -3.33，P = 0.0009）观察到腿部RC斜率显著下降，表明在卧床休息后的即刻阶段皮质脊髓兴奋性出现组内下降，并在接下来的2周内恢复至接近基线水平。仅在P2（t(2916)= 1.97，P = 0.049）、P3（t(2916)= -2.12，P = 0.034）和P12（t(2916)= -2.19，P = 0.029）观察到手部RC斜率有显著影响；在P0（t(2916)= -1.32，无统计学意义）、P1（t(2916)= 1.00，无统计学意义）、P5（t(2916)= -0.21，无统计学意义）或P8（t(2916)= -0.27，无统计学意义）各天未观察到显著影响。fMRI显示手部激活无变化，但腿部在卧床休息后激活增加。在个体层面，发现了更具异质性的反应，这显示出与FMT表现的潜在关联。
本研究结果包括对与腿部废用相关的皮质可塑性有了更好的理解，并可能在患者和宇航员康复中得到应用。
