Kariminezhad Shohreh, Karhu Jari, Säisänen Laura, Reijonen Jusa, Könönen Mervi, Julkunen Petro
Department of Applied Physics, University of Eastern Finland, 70211 Kuopio, Finland.
Department of Clinical Neurophysiology, Kuopio University Hospital, 70029 Kuopio, Finland.
Brain Sci. 2020 Sep 26;10(10):674. doi: 10.3390/brainsci10100674.
Repetition suppression (RS), i.e., the reduction of neuronal activity upon repetition of an external stimulus, can be demonstrated in the motor system using transcranial magnetic stimulation (TMS). We evaluated the RS in relation to the neuroplastic changes induced by paired associative stimulation (PAS). An RS paradigm, consisting of 20 trains of four identical suprathreshold TMS pulses 1 s apart, was assessed for motor-evoked potentials (MEPs) in 16 healthy subjects, before and following (at 0, 10, and 20 min) a common PAS protocol. For analysis, we divided RS into two components: (1) the ratio of the second MEP amplitude to the first one in RS trains, i.e., the "dynamic" component, and (2) the mean of the second to fourth MEP amplitudes, i.e., the "stable" component. Following PAS, five subjects showed change in the dynamic RS component. However, nearly all the individuals ( = 14) exhibited change in the stable component ( < 0.05). The stable component was similar between subjects showing increased MEPs and those showing decreased MEPs at this level ( = 0.254). The results suggest the tendency of the brain towards a stable state, probably free from the ongoing dynamics, following PAS.
重复抑制（RS），即重复外部刺激时神经元活动的减少，可通过经颅磁刺激（TMS）在运动系统中得到证实。我们评估了与配对联想刺激（PAS）诱导的神经可塑性变化相关的重复抑制。在16名健康受试者中，在一个常见的PAS方案之前和之后（0、10和20分钟时），采用由20组四个相同的阈上TMS脉冲组成、脉冲间隔为1秒的重复抑制范式评估运动诱发电位（MEP）。为了进行分析，我们将重复抑制分为两个部分：（1）重复抑制序列中第二个MEP波幅与第一个的比值，即“动态”部分；（2）第二个至第四个MEP波幅的平均值，即“稳定”部分。PAS后，5名受试者的动态重复抑制部分出现变化。然而，几乎所有个体（n = 14）的稳定部分都出现了变化（P < 0.05）。在这一水平上，MEP增加的受试者和MEP减少的受试者之间的稳定部分相似（P = 0.254）。结果表明，PAS后大脑倾向于一种稳定状态，可能不受持续动态变化的影响。
