Stephani Caspar, Paulus Walter, Sommer Martin
Department of Clinical Neurophysiology, University of Göttingen, Göttingen, Germany
Department of Clinical Neurophysiology, University of Göttingen, Göttingen, Germany.
Physiol Rep. 2016 Jan;4(1). doi: 10.14814/phy2.12666.
The objective of this study was to investigate the significance of pulse configurations and current direction for corticospinal activation using transcranial magnetic stimulation (TMS). In 11 healthy subjects (8 female), a motor map for the motor evoked potentials (MEPs) recorded from the first dorsal interosseus (FDI), abductor digiti minimi (ADM), extensor carpi radialis, and biceps brachii (BB) muscles of the dominant side was established. Starting from a manually determined hot spot of the FDI representation, we measured MEPs at equal oriented points on an hexagonal grid, with 7 MEPs recorded at each point, using the following pulse configurations: posteriorly directed monophasic (Mo-P), anteriorly directed monophasic (Mo-A), biphasic with the more relevant second cycle oriented posteriorly (Bi-P) as well as a reversed biphasic condition (Bi-A). For each pulse configuration, a hot spot was determined and a center of gravity (CoG) was calculated. We found that the factor current direction had an effect on location of the CoG-adjusted hot spot in the cranio-caudal axis but not in the latero-medial direction with anteriorly directed pulses locating the CoG more anteriorly and vice versa. In addition, the CoG for the FDI was more laterally than the cortical representations for the abductor digiti minimi (ADM) and extensor carpi radialis (ECR) which were registered as well. The results indicate that direction of the current pulse should be taken into account for determination of the motor representation of a muscle by TMS.
本研究的目的是利用经颅磁刺激（TMS）研究脉冲配置和电流方向对皮质脊髓激活的意义。在11名健康受试者（8名女性）中，建立了优势侧第一背侧骨间肌（FDI）、小指展肌（ADM）、桡侧腕伸肌和肱二头肌（BB）肌肉记录的运动诱发电位（MEP）的运动图谱。从手动确定的FDI代表区热点开始，我们在六边形网格上的等方向点测量MEP，每个点记录7个MEP，使用以下脉冲配置：向后定向的单相（Mo-P）、向前定向的单相（Mo-A）、第二个更相关周期向后定向的双相（Bi-P）以及反向双相条件（Bi-A）。对于每种脉冲配置，确定一个热点并计算重心（CoG）。我们发现，电流方向因素对CoG调整后的热点在颅尾轴上的位置有影响，但在内外侧方向上没有影响，向前定向的脉冲使CoG更靠前，反之亦然。此外，FDI的CoG比记录的小指展肌（ADM）和桡侧腕伸肌（ECR）的皮质代表区更靠外侧。结果表明，在通过TMS确定肌肉的运动代表区时应考虑电流脉冲的方向。
