Pulse Duration as Well as Current Direction Determines the Specificity of Transcranial Magnetic Stimulation of Motor Cortex during Contraction.
Pulse Duration as Well as Current Direction Determines the Specificity of Transcranial Magnetic Stimulation of Motor Cortex during Contraction.
复制标题
脉冲持续时间以及电流方向决定了收缩过程中运动皮层的经颅磁刺激的特异性。
DOI：
10.1016/j.brs.2016.09.008
复制
发表时间：
2017-01
影响因子：
7.7
通讯作者：
Rothwell JC
中科院分区：
文献类型：
--
作者：
Hannah R;Rothwell JC
通过控制电流方向和脉冲持续时间，可以实现对皮质脊髓神经元输入的选择性刺激。短暂（30 μs）前后电流招募的神经群对体感觉输入表现出最大的敏感性。脉冲持续时间是决定经颅磁刺激在人体运动皮层中激活的重要因素。先前的研究表明，经颅磁刺激在运动皮层（M1）诱导的前后定向电流（AP）激活的神经元中间回路与后前定向电流（PA）激活的神经元中间回路不同。本实验提供的证据表明，脉冲持续时间也决定了特定神经元中间回路的激活。采用单运动单元（SMU）记录，确认AP30、AP120、PA30和PA120不同电流方向和脉冲持续时间所诱发的运动诱发电位（MEPs）起潜伏期的差异。测试mep的振幅是否受到来自手部的体感输入（短潜伏期传入抑制，SAI）的不同影响，并检查SAI对直流电刺激（tDCSCb）产生的小脑兴奋性变化的敏感性。记录第一背骨间肌的表面肌电图和smu。通过可控脉冲参数TMS （cTMS）装置，在经颅磁刺激（TMS）前20-25 ms对手M1区进行正中神经或指神经电刺激，测试SAI。在应用阳极或假tDCSCb期间也检测了SAI。由于低刺激强度时TMS脉冲特异性最强，因此大多数实验采用弱自愿收缩来降低刺激阈值。AP30电流招募了最长潜伏期的SMU和表面MEP反应。在收缩期间，AP30反应的SAI高于所有其他脉冲。在线阳极tDCSCb只降低了AP30电流的SAI。AP30电流激活的中间神经元电路具有不同于其他脉冲类型激活的功能特性。脉冲持续时间和电流方向决定了在经颅磁刺激下M1被激活的是什么。
Selective stimulation of inputs to corticospinal neurons may be achieved by manipulating current direction and pulse duration. Neural populations recruited by brief (30 μs) anterior–posterior currents exhibited the greatest sensitivity to somatosensory input. Pulse duration is an important determinant of what is activated with TMS in human motor cortex. Previous research suggested that anterior–posterior (AP) directed currents induced by TMS in motor cortex (M1) activate interneuron circuits different from those activated by posterior–anterior currents (PA). The present experiments provide evidence that pulse duration also determines the activation of specific interneuron circuits. To use single motor unit (SMU) recordings to confirm the difference in onset latencies of motor-evoked potentials (MEPs) evoked by different current directions and pulse durations: AP30, AP120, PA30 and PA120. To test whether the amplitude of the MEPs is differentially influenced by somatosensory inputs from the hand (short-latency afferent inhibition, SAI), and examine the sensitivity of SAI to changes in cerebellar excitability produced by direct current stimulation (tDCSCb). Surface electromyograms and SMUs were recorded from the first dorsal interosseous muscle. SAI was tested with an electrical stimulus to median or digital nerves ~20–25 ms prior to TMS delivered over the M1 hand area via a controllable pulse parameter TMS (cTMS) device. SAI was also tested during the application of anodal or sham tDCSCb. Because TMS pulse specificity is greatest at low stimulus intensities, most experiments were conducted with weak voluntary contraction to reduce stimulus threshold. AP30 currents recruited the longest latency SMU and surface MEP responses. During contraction SAI was greater for AP30 responses versus all other pulses. Online anodal tDCSCb reduced SAI for the AP30 currents only. AP30 currents activate an interneuron circuit with functional properties different from those activated by other pulse types. Pulse duration and current direction determine what is activated in M1 with TMS.