Lucarelli Delia, Guidali Giacomo, Sulcova Dominika, Zazio Agnese, Bonfiglio Natale Salvatore, Stango Antonietta, Barchiesi Guido, Bortoletto Marta
Neurophysiology Lab, IRCCS Istituto Centro San Giovanni di Dio Fatebenefratelli, Brescia, Italy.
Department of Neuroscience, Imaging and Clinical Sciences, University of Chieti-Pescara, Chieti, Italy.
Brain Topogr. 2025 Mar 28;38(3):39. doi: 10.1007/s10548-025-01113-2.
Transcranial magnetic stimulation (TMS)-evoked potentials (TEPs) represent an innovative measure for examining brain connectivity and developing biomarkers of psychiatric conditions. Minimizing TEP variability across studies and participants, which may stem from methodological choices, is therefore vital. By combining classic peak analysis and microstate investigation, we tested how TMS pulse waveform and current direction may affect cortico-cortical circuit engagement when targeting the primary motor cortex (M1). We aim to disentangle whether changing these parameters affects the degree of activation of the same neural circuitry or may lead to changes in the pathways through which the induced activation spreads. Thirty-two healthy participants underwent a TMS-EEG experiment in which the pulse waveform (monophasic, biphasic) and current direction (posterior-anterior, anterior-posterior, latero-medial) were manipulated. We assessed the latency and amplitude of M1-TEP components and employed microstate analyses to test differences in topographies. Results revealed that TMS parameters strongly influenced M1-TEP components' amplitude but had a weaker role over their latencies. Microstate analysis showed that the current direction in monophasic stimulations changed the pattern of evoked microstates at the early TEP latencies, as well as their duration and global field power. This study shows that the current direction of monophasic pulses may modulate cortical sources contributing to TEP signals, activating neural populations and cortico-cortical paths more selectively. Biphasic stimulation reduces the variability associated with current direction and may be better suited when TMS targeting is blind to anatomical information.
经颅磁刺激（TMS）诱发的电位（TEP）是一种用于检查脑连接性和开发精神疾病生物标志物的创新手段。因此，尽量减少不同研究和参与者之间TEP的变异性（这可能源于方法学选择）至关重要。通过结合经典的峰值分析和微状态研究，我们测试了在针对初级运动皮层（M1）时，TMS脉冲波形和电流方向如何影响皮质-皮质回路的参与情况。我们旨在弄清楚改变这些参数是会影响同一神经回路的激活程度，还是会导致诱发激活传播途径的改变。32名健康参与者进行了一项TMS-脑电图实验，其中对脉冲波形（单相、双相）和电流方向（后-前、前-后、外侧-内侧）进行了操控。我们评估了M1-TEP成分的潜伏期和振幅，并采用微状态分析来测试地形图的差异。结果显示，TMS参数对M1-TEP成分的振幅有强烈影响，但对其潜伏期的影响较弱。微状态分析表明，单相刺激中的电流方向在TEP早期潜伏期改变了诱发微状态的模式，以及它们的持续时间和全局场功率。这项研究表明，单相脉冲的电流方向可能会调节对TEP信号有贡献的皮质源，更有选择性地激活神经群体和皮质-皮质路径。双相刺激减少了与电流方向相关的变异性，当TMS靶向对解剖信息不明确时可能更适用。
