PDF(Pubmed)
Abstract：
Objective.The transcranial magnetic stimulation (TMS) coil induces an electric field that diminishes rapidly upon entering the brain. This presents a challenge in achieving focal stimulation of a deep brain structure. Neuronal elements, including axons, dendrites, and cell bodies, exhibit specific time constants. When exposed to repetitive TMS pulses at a high frequency, there is a cumulative effect on neuronal membrane potentials, resulting in temporal summation. This study aims to determine whether TMS pulse train at high-frequency and subthreshold intensity could induce a suprathreshold response.Approach.As a proof of concept, we developed a TMS machine in-house that could consistently output pulses up to 250 Hz, and performed experiments on 22 awake rats to test whether temporal summation was detectable under pulse trains at 100, 166, or 250 Hz.Main results.Results revealed that TMS pulses at 55% maximum stimulator output (MSO, peak dI/dt= 68.5 A/μs at 100% MSO, pulse width = 48μs) did not induce motor responses with either single pulses or pulse trains. Similarly, a single TMS pulse at 65% MSO failed to evoke a motor response in rats; however, a train of TMS pulses at frequencies of 166 and 250 Hz, but not at 100 Hz, successfully triggered motor responses and MEP signals, suggesting a temporal summation effect dependent on both pulse intensities and pulse train frequencies.Significance.We propose that the temporal summation effect can be leveraged to design the next-generation focal TMS system: by sequentially driving multiple coils at high-frequency and subthreshold intensity, areas with the most significant overlapping E-fields undergo maximal temporal summation effects, resulting in a suprathreshold response.
摘要：
目的：经颅磁刺激（TMS）线圈感应的电场在进入大脑时迅速减弱。这在实现深部脑结构的病灶刺激方面提出了挑战。神经元元素,包括轴突,树突,和细胞体，表现出特定的时间常数。当暴露于高频率的重复TMS脉冲时，对神经元膜电位有累积效应，导致时间求和。这项研究旨在确定高频和亚阈值强度的TMS脉冲串是否会引起超阈值反应。
方法：作为概念证明，我们在内部开发了一种TMS机器，可以持续输出高达250Hz的脉冲，并对22只清醒的大鼠进行了实验，以测试在100、166或250Hz的脉冲序列下是否可以检测到时间总和。
结果：结果显示，TMS在最大刺激器输出为55％时发出脉冲（MSO，在100%MSO时，峰值dI/dt=68.5A/µs，脉冲宽度=48µs)不会诱导单脉冲或脉冲序列的运动响应。同样，65％MSO的单个TMS脉冲无法引起大鼠的运动反应；然而，一系列频率为166和250Hz的TMS脉冲，但不是在100赫兹，成功触发电机响应和MEP信号，表明时间求和效应取决于脉冲强度和脉冲串频率。
结论：我们建议可以利用时间求和效应来设计下一代焦点TMS系统：通过以高频和亚阈值强度顺序驱动多个线圈，具有最显著重叠电场的区域经历最大时间求和效应，导致超阈值反应。
方法：作为概念证明，我们在内部开发了一种TMS机器，可以持续输出高达250Hz的脉冲，并对22只清醒的大鼠进行了实验，以测试在100、166或250Hz的脉冲序列下是否可以检测到时间总和。
结果：结果显示，TMS在最大刺激器输出为55％时发出脉冲（MSO，在100%MSO时，峰值dI/dt=68.5A/µs，脉冲宽度=48µs)不会诱导单脉冲或脉冲序列的运动响应。同样，65％MSO的单个TMS脉冲无法引起大鼠的运动反应；然而，一系列频率为166和250Hz的TMS脉冲，但不是在100赫兹，成功触发电机响应和MEP信号，表明时间求和效应取决于脉冲强度和脉冲串频率。
结论：我们建议可以利用时间求和效应来设计下一代焦点TMS系统：通过以高频和亚阈值强度顺序驱动多个线圈，具有最显著重叠电场的区域经历最大时间求和效应，导致超阈值反应。
