Sauner Dieter, Bestmann Sven, Siebner Hartwig R, Rothwell John C
Sobell Department of Motor Neuroscience and Movement Disorders, Institute of Neurology, University College London, 8-11 Queen Square, London WC1N 3BG, UK.
Eur J Neurosci. 2006 Apr;23(8):2215-24. doi: 10.1111/j.1460-9568.2006.04731.x.
Twelve right-handed volunteers were asked to judge the laterality of a hand stimulus by pressing a button with one of their toes. Judgements were based on two-dimensional drawings of the back or palm of a right or left hand at various orientations. Suprathreshold single-pulse transcranial magnetic stimulation (TMS) was given to the left primary motor hand area (M1-HAND) at 0, 200, 400, 600, 800 or 1000 ms after stimulus onset to probe the functional involvement of the dominant left M1 at various stages of handedness recognition. We found that mean reaction times and error rates increased with angle of rotation depending on the actual biomechanical constraints of the hand but suprathreshold TMS had no influence on task performance regardless of the timing of TMS. However, the excitability of the corticomotor output from the left M1-HAND was modulated during the reaction. Judging left hand drawings was associated with an attenuation of motor-evoked potentials 300-100 ms before the response, whereas judging right hand drawings facilitated the motor-evoked potentials only immediately before the response. These effects were the same for pictures of backs and palms and were independent of the angle of rotation. The failure of TMS to affect task performance suggests that there is no time window during which the M1-HAND makes a critical contribution to mental rotation of the hand. The modulation of motor-evoked potentials according to the laterality of the stimulus indicates a secondary effect of the task on corticomotor excitability that is not directly related to mental rotation itself.
12名右利手志愿者被要求用脚趾按按钮来判断手部刺激的偏向性。判断基于右手或左手背部或手掌在不同方向的二维绘图。在刺激开始后0、200、400、600、800或1000毫秒，对左侧初级运动手部区域（M1-HAND）给予阈上单脉冲经颅磁刺激（TMS），以探究优势侧左M1在 handedness识别不同阶段的功能参与情况。我们发现，平均反应时间和错误率随着旋转角度的增加而增加，这取决于手部实际的生物力学限制，但阈上TMS对任务表现没有影响，无论TMS的时机如何。然而，在反应过程中，来自左M1-HAND的皮质运动输出的兴奋性受到了调制。判断左手绘图与反应前300 - 100毫秒运动诱发电位的衰减有关，而判断右手绘图仅在反应前立即促进运动诱发电位。这些效应对于背部和手掌的图片是相同的，并且与旋转角度无关。TMS未能影响任务表现表明，不存在M1-HAND对手部心理旋转做出关键贡献的时间窗口。根据刺激的偏向性对运动诱发电位的调制表明，该任务对皮质运动兴奋性有次要影响，这与心理旋转本身没有直接关系。
