Svensson Peter, Romaniello Antonietta, Arendt-Nielsen Lars, Sessle Barry J
Orofacial Pain Laboratory, Center for Sensory-Motor Interaction, Aalborg University, Aalborg, Denmark.
Exp Brain Res. 2003 Sep;152(1):42-51. doi: 10.1007/s00221-003-1517-2. Epub 2003 Jun 26.
Transcranial magnetic stimulation (TMS) has been used to assess characteristics of the corticomotor control of the jaw muscles, but less is known about the cortical control of the human tongue and its modification by training. The aim of the present study was to determine the effect of training humans in a novel tongue-protrusion task for 1 week on corticomotor excitability as assessed by changes in electromyographic activity elicited in the tongue musculature by TMS, and in the tongue cortical motor map revealed by TMS. Eleven healthy subjects participated. Stimulus-response curves were generated from the motor evoked potentials (MEPs) recorded in the tongue musculature and, from the first dorsal interosseos (FDI) muscle as a control, at three time periods: at baseline, immediately after the 1-week training period, and at 2-weeks follow-up. In addition, the corticomotor representations of the tongue and FDI muscles were mapped on a 1 x 1 cm scalp grid. The tongue-training task required each subject to protrude the tongue onto a force transducer placed in front of the subject, and consisted of a relax-protrude-hold-relax cycle lasting 12.5 s with 1 N as the target at the hold phase. The subjects repeated this task for 60 min every day for 1 week. All subjects reported moderate levels of fatigue in the tongue during the first training day; however, these subjective reports decreased during the week (ANOVA P<0.001), and the subjects showed a progressive increase in their ability to perform the task successfully ( P<0.001). The threshold for evoking MEPs by TMS in the tongue musculature was significantly decreased after the last training day compared with baseline and the 2-weeks follow-up ( P<0.001). The amplitude of the MEPs in the tongue musculature was significantly increased at higher intensities of TMS after the last training day but returned to baseline values at the 2-weeks follow-up (P = 0.005). No significant effect of the training on MEPs in the FDI was observed (P = 0.493). Analysis of the corticomotor topographic maps revealed a significant ( P<0.05) increase in excitability and, hence, the cortical area from which TMS could evoke MEPs in the tongue, although the center of gravity representation for the tongue or FDI muscles remained stable. The present findings suggest that a specific and reversible plasticity of the corticomotor excitability related to tongue muscle control can be induced when humans learn to perform successfully a novel tongue task.
经颅磁刺激（TMS）已被用于评估下颌肌肉皮质运动控制的特征，但对于人类舌肌的皮质控制及其训练后的变化了解较少。本研究的目的是确定让人类进行为期1周的新型伸舌任务训练对皮质运动兴奋性的影响，这一影响通过TMS诱发舌肌肌电图活动的变化以及TMS显示的舌皮质运动图谱来评估。11名健康受试者参与了研究。在三个时间段生成了刺激 - 反应曲线，分别是：基线期、1周训练期结束后即刻以及2周随访期，曲线基于记录在舌肌和作为对照的第一骨间背侧肌（FDI）中的运动诱发电位（MEP）生成。此外，在1×1平方厘米的头皮网格上绘制了舌肌和FDI肌肉的皮质运动代表区。舌部训练任务要求每个受试者将舌头伸到放置在受试者前方的力传感器上，由一个持续12.5秒的放松 - 伸出 - 保持 - 放松周期组成，保持阶段的目标力为1牛顿。受试者每天重复此任务60分钟，持续1周。所有受试者在训练的第一天都报告舌部有中度疲劳感；然而，这些主观报告在一周内有所减少（方差分析P<0.001），并且受试者成功完成任务的能力逐渐增强（P<0.001）。与基线期和2周随访期相比，最后一个训练日之后，TMS诱发舌肌MEP的阈值显著降低（P<0.001）。在最后一个训练日之后，当TMS强度较高时，舌肌MEP的波幅显著增加，但在2周随访期恢复到基线值（P = 0.005）。未观察到训练对FDI中MEP有显著影响（P = 0.493）。对皮质运动地形图的分析显示，尽管舌肌或FDI肌肉的重心代表区保持稳定，但舌肌的兴奋性显著增加（P<0.05），因此，TMS能够诱发舌肌MEP的皮质区域增大。目前的研究结果表明，当人类学会成功执行一项新型舌部任务时，与舌肌控制相关的皮质运动兴奋性会出现特定的、可逆的可塑性变化。
