Kähkönen Seppo, Ilmoniemi Risto J
BioMag Laboratory, Engineering Centre, Helsinki University Central Hospital and Cognitive Brain Research Unit, Department of Psychology, University of Helsinki, Helsinki, Finland.
J Psychopharmacol. 2004 Jun;18(2):257-61. doi: 10.1177/0269881104042631.
Transcranial magnetic stimulation (TMS) provides new possibilities for studying localized changes in the electrical properties of the human cortex. TMS combined with electromyography (EMG) has revealed that drugs blocking Na(+) or Ca(2+) channels such as phenytoin, lamotrigin or carbamazepine change the motor threshold without affecting intracortical inhibition or facilitation. Gabaergic agents vigabatrin, lorazepam, diazepam, baclofen and ethanol do not affect the motor threshold, but increase intracortical inhibition and decrease facilitation. N-methyl-D-aspartate receptor antagonists riluzole, dextromethorphan and memantine have similar effects. Dopamine receptor antagonists such as haloperidol, but not sulpiride, decrease intracortical inhibition and increase intracortical facilitation. Other monoamines, such as serotonin and noradrenaline, may have some modulating effect on the cortical excitability. However, TMS combined with EMG gives only indirect evidence about the excitability of the motor cortex because spinal mechanisms may contribute to the results. Cortical excitability can be studied directly by combining TMS with brain imaging methods such as electroencephalography (EEG). Motor and non-motor areas can be stimulated and subsequent brain activity can be measured. Ethanol has been shown to modulate EEG responses evoked by motor-cortex TMS, the effects being largest at the right prefrontal cortex, meaning that ethanol would have changed the functional connectivity. Furthermore, alcohol decreases amplitudes of EEG responses after the left prefrontal stimulation mainly in anterior parts of the cortex, which may be associated with the decrease of the prefrontal cortical excitability. Taken together, TMS provides a new insight to the actions of central nervous system drugs at the cortical level.
经颅磁刺激（TMS）为研究人类皮质电特性的局部变化提供了新的可能性。TMS与肌电图（EMG）相结合已表明，阻断Na(+)或Ca(2+)通道的药物，如苯妥英、拉莫三嗪或卡马西平，会改变运动阈值，而不影响皮质内抑制或易化。γ-氨基丁酸能药物氨己烯酸、劳拉西泮、地西泮、巴氯芬和乙醇不影响运动阈值，但会增加皮质内抑制并减少易化。N-甲基-D-天冬氨酸受体拮抗剂利鲁唑、右美沙芬和美金刚具有类似作用。多巴胺受体拮抗剂，如氟哌啶醇，但不包括舒必利，会减少皮质内抑制并增加皮质内易化。其他单胺类物质，如5-羟色胺和去甲肾上腺素，可能对皮质兴奋性有一定的调节作用。然而，TMS与EMG相结合只能提供关于运动皮质兴奋性的间接证据，因为脊髓机制可能会对结果产生影响。通过将TMS与脑成像方法，如脑电图（EEG）相结合，可以直接研究皮质兴奋性。可以刺激运动和非运动区域，并测量随后的脑活动。乙醇已被证明可调节运动皮质TMS诱发的EEG反应，其效应在右侧前额叶皮质最为明显，这意味着乙醇会改变功能连接。此外，酒精主要在皮质前部降低左侧前额叶刺激后EEG反应的幅度，这可能与前额叶皮质兴奋性降低有关。综上所述，TMS为中枢神经系统药物在皮质水平的作用提供了新的见解。
