Borghetti D, Sartucci F, Petacchi E, Guzzetta A, Piras M F, Murri L, Cioni G
Department of Neuroscience, Clinical Neurology, University of Pisa, Italy.
Brain Res Bull. 2008 Sep 30;77(2-3):143-8. doi: 10.1016/j.brainresbull.2008.06.001. Epub 2008 Jun 26.
Transcranial magnetic stimulation (TMS) is a non-invasive method to investigate motor pathways and to create a map of the somatotopical organization of the motor cortex: ordinary mapping procedures requires a focal brain stimulation over different spots of the scalp and electromyographic (EMG) recording from a muscle. Finding an appropriate and a valid visual representation of collected data is a crucial step in research and clinical field to allow a relatively fast, intra- and inter-patient comparison of motor cortex mapping. Aim of this study was to develop and to validate a method to map cortical representation of an intrinsic hand muscle (abductor digiti minimi, ADM) using a two-dimensional spline interpolation of EMG peak amplitudes obtained with TMS. The interpolated model will result in a graphical colour-scaled representation of the motor cortex for the investigated muscle; fitted model was finally validated by comparing derived parameters with those directly measured to ensure the strength and reliability of the model. Ten healthy volunteers (mean age+/-S.D.: 35.3+/-4.7 years, 4 males and 6 females) were enrolled in the study. Transcranial stimulation was performed by placing a figure-of-eight coil over a predefined grid on the scalp of the subject. EMG responses were recorded from the right abductor digiti minimi (ADM): averaged EMG peak amplitudes obtained at each node were then used to perform spline interpolation and to derive other parameters like center of gravity (CoG). Arithmetical mean of all resting motor threshold at the hotspot was 50.6+/-3.4% of the maximal stimulator output. Average amplitude at the hotspot was 1.72+/-0.80 mV and its coordinates, expressed as median, were x=4.5 cm and y=0.0 cm. Mean CoG was located at x=4.86+/-0.57 cm and y=0.35+/-0.10 cm. Mean interpolated peak coordinates for ADM were xf=4.86+/-0.58 cm and yf=0.36+/-0.12 cm, while mean fitted peak amplitude was 0.87+/-0.47 mV. Results suggest how it is possible to map the primary motor cortex using two-dimensional spline interpolation of peak-to-peak amplitudes obtained by single pulse TMS delivered on several scalp positions, which will result in a smooth, easy to read, colour-scaled map. However, like other visual representation modalities, the interpolation should become complementary to traditional methods and not a substitute of a precise and accurate cortical motor mapping.
经颅磁刺激（TMS）是一种用于研究运动通路以及绘制运动皮质躯体感觉组织图谱的非侵入性方法：常规的图谱绘制程序需要在头皮的不同部位进行局灶性脑刺激，并从一块肌肉记录肌电图（EMG）。在研究和临床领域，找到一种合适且有效的收集数据的视觉呈现方式，对于实现相对快速的患者内和患者间运动皮质图谱比较至关重要。本研究的目的是开发并验证一种方法，该方法利用经颅磁刺激获得的肌电图峰值振幅的二维样条插值来绘制手部固有肌（小指展肌，ADM）的皮质表征。插值模型将生成所研究肌肉的运动皮质的图形化颜色标度表示；最终通过将导出参数与直接测量的参数进行比较来验证拟合模型，以确保模型的强度和可靠性。十名健康志愿者（平均年龄±标准差：35.3±4.7岁，4名男性和6名女性）参与了本研究。通过将一个8字形线圈放置在受试者头皮上的预定义网格上进行经颅刺激。从小指展肌（ADM）记录肌电图反应：然后使用在每个节点获得的平均肌电图峰值振幅进行样条插值，并导出其他参数，如重心（CoG）。热点处所有静息运动阈值的算术平均值为最大刺激器输出的50.6±3.4%。热点处的平均振幅为1.72±0.80 mV，其坐标（以中位数表示）为x = 4.5 cm和y = 0.0 cm。平均重心位于x = 4.86±0.57 cm和y = 0.35±0.10 cm处。小指展肌的平均插值峰值坐标为xf = 4.86±0.58 cm和yf = 0.36±0.12 cm，而平均拟合峰值振幅为0.87±0.47 mV。结果表明，通过对在多个头皮位置施加的单脉冲经颅磁刺激获得的峰峰值振幅进行二维样条插值，可以绘制初级运动皮质，这将生成一个平滑、易于阅读的颜色标度图谱。然而，与其他视觉呈现方式一样，插值应成为传统方法的补充，而不是精确准确的皮质运动图谱的替代品。
