Maeda F, Keenan J P, Tormos J M, Topka H, Pascual-Leone A
Department of Neurology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
Exp Brain Res. 2000 Aug;133(4):425-30. doi: 10.1007/s002210000432.
Repetitive transcranial magnetic stimulation (rTMS) appears to have effects on cortical excitability that extend beyond the train of rTMS itself. These effects may be inhibitory or facilitatory and appear to depend on the frequency, intensity, duration and intertrain interval of the rTMS. Many studies assume facilitatory effects of high-frequency rTMS and inhibitory effects of low-frequency rTMS. Nevertheless, the interindividual variability of this modulation of cortical excitability by rTMS has not been systematically investigated. In this study, we applied 240 pulses of rTMS at 90% of the subjects' motor threshold to their motor cortex at different frequencies (1, 10, 15 and 20 Hz) and examined the effects on motor evoked potentials (frequency tuning curve). Although the averaged group data showed a frequency-dependent increase in cortical excitability, each subject had a different pattern of frequency tuning curve, i.e. a different modulatory effect on cortical excitability at different rTMS frequencies. The interindividual variability of these modulatory effects was still high, though less so, when the number of rTMS pulses was increased to 1,600. These findings illustrate the degree of variability of the rTMS effects in the human brain.
重复经颅磁刺激（rTMS）似乎对皮质兴奋性有影响，且这种影响超出了rTMS本身的刺激序列。这些影响可能是抑制性的或易化性的，并且似乎取决于rTMS的频率、强度、持续时间和刺激间隔。许多研究假定高频rTMS具有易化作用，低频rTMS具有抑制作用。然而，rTMS对皮质兴奋性调节的个体间变异性尚未得到系统研究。在本研究中，我们以受试者运动阈值的90%，在不同频率（1、10、15和20Hz）对其运动皮质施加240个rTMS脉冲，并检查对运动诱发电位的影响（频率调谐曲线）。尽管平均的组数据显示皮质兴奋性随频率增加，但每个受试者都有不同的频率调谐曲线模式，即在不同rTMS频率下对皮质兴奋性有不同的调节作用。当rTMS脉冲数增加到1600时，这些调节作用的个体间变异性仍然很高，尽管变异性有所降低。这些发现说明了rTMS效应在人脑中的变异程度。
