Westmead Clinical School, University of Sydney, Australia.
Brain and Mind Center, University of Sydney, Australia.
Clin Neurophysiol. 2020 May;131(5):1000-1010. doi: 10.1016/j.clinph.2020.02.012. Epub 2020 Mar 3.
Recruitment of interneuronal circuits generating later indirect (I) waves seem to be important in short-interval intracortical inhibition (SICI) and facilitation (SICF) development. This study assessed whether individual variations in intracortical inhibition and facilitation could be explained by variation in recruitment of interneuronal networks.
Cortical excitability was assessed using a figure of eight coil, with motor evoked responses recorded over the contralateral abductor pollicis brevis (APB) muscle. I-wave recruitment was inferred from the measurement of motor evoked potential (MEP) onset latencies, with coil positioned in posterior-to-anterior (early I waves) and anterior-to-posterior (later I waves) directions.
Subtle variability in the recruitment of later I-waves (I3) was evident across subjects. Importantly, mean SICI (P < 0.05) was significantly greater in subjects recruiting I3 waves, as were the two SICI peaks at interstimulus intervals of 1 ms (P < 0.05) and 3 ms (P < 0.05). In addition, mean SICF was significantly greater in participants exhibiting an AP-to-LM latency differences of <4 ms (P < 0.01). There was no significant correlation between I-wave recruitment and intracortical facilitation, motor evoked potential amplitude or cortical silent period duration.
Differential recruitment of interneuronal networks appears to underlie the generation and individual variations in intracortical inhibition and facilitation.
Investigating cortical interneuronal networks in human diseases may yield novel pathophysiological insights.
募集产生后期间接（I）波的中间神经元回路似乎在短程皮质内抑制（SICI）和易化（SICF）发展中很重要。本研究评估了皮质内抑制和易化的个体变异是否可以通过中间神经元网络募集的变异来解释。
使用 8 字形线圈评估皮质兴奋性，通过对对侧外展拇指短肌（APB）记录运动诱发电位（MEP）来记录 I 波募集。通过测量运动诱发电位（MEP）起始潜伏期来推断 I 波募集，线圈放置在后前（早期 I 波）和前后（后期 I 波）方向。
在受试者中，后期 I 波（I3）的募集存在细微的变异性。重要的是，在募集 I3 波的受试者中，SICI 均值（P < 0.05）显著更高，且在刺激间隔为 1 毫秒（P < 0.05）和 3 毫秒（P < 0.05）时，SICI 出现两个高峰。此外，在表现出 AP 至 LM 潜伏期差异<4ms 的参与者中，SICF 均值显著更高（P < 0.01）。I 波募集与皮质内易化、运动诱发电位幅度或皮质静息期持续时间之间无显著相关性。
中间神经元网络的差异募集似乎是皮质内抑制和易化产生和个体变异的基础。
在人类疾病中研究皮质中间神经元网络可能会产生新的病理生理学见解。
