Transcranial magnetic stimulation (TMS) is used frequently to study human physiology, including the indirect-wave (I-wave) circuits generating short-interval intracortical facilitation (SICF). Growing evidence implicates SICF in plasticity and motor learning, suggesting that SICF is likely of functional relevance in both health and disease. To date, test-retest reliability has not been established for measures of SICF: given the clear potential of SICF to be used as a diagnostic tool, it is critical to establish the reliability of the paired-pulse TMS protocol to measure SICF. We investigated the test-retest reliability of SICF measured using paired-pulse TMS. SICF was measured in two sessions in 20 young adults using single- and paired-pulse TMS. Single-pulse TMS was set at an intensity that elicited MEPs of 1 mV (SI1mV) and paired-pulse TMS was set with the first stimulus at SI1mV, the second stimulus (S2) 90% of resting motor threshold (RMT), and a total of 20 interstimulus intervals (ISI; 1.1-4.9 ms with a 0.2 ms step). Large intraclass correlation coefficients (ICC) indicate good test-retest reliability between sessions for all SICF peaks (ICCs ranging from 0.73 to 0.79). The ISI at which SICF was maximal within individuals was consistent at all three peaks across both experimental sessions. Results showed good test-retest reliability of SICF at all three peaks when using a standard paired-pulse protocol to measure SICF. This finding suggests that paired-pulse TMS can be used to reliably probe the excitability of the interneuronal circuits that generate SICF. This provides a strong platform for future research to investigate the functional role of I-wave circuitry, including the role of I-wave circuitry in motor control decline in healthy older adults and individuals with movement disorders.

中文翻译：

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用于测量短间隔皮质内促进的配对脉冲经颅磁刺激方案的良好测试-再测试可靠性。

经颅磁刺激 (TMS) 经常用于研究人体生理学，包括产生短间隔皮质内促进 (SICF) 的间接波 (I 波) 电路。越来越多的证据表明 SICF 与可塑性和运动学习有关，这表明 SICF 可能与健康和疾病的功能相关。迄今为止，尚未确定 SICF 测量的重测可靠性：鉴于 SICF 作为诊断工具的明显潜力，建立配对脉冲 TMS 协议的可靠性以测量 SICF 至关重要。我们研究了使用配对脉冲 TMS 测量的 SICF 的重测可靠性。SICF 是在 20 名年轻人中使用单脉冲和双脉冲 TMS 在两个会话中测量的。单脉冲 TMS 的强度设置为引起 1 mV (SI1mV) 的 MEP，成对脉冲 TMS 设置为第一个刺激为 SI1mV，第二个刺激 (S2) 为静息运动阈值 (RMT) 的 90%，以及总共 20 个刺激间隔（ISI；1.1-4.9 毫秒，步长为 0.2 毫秒）。大的组内相关系数 (ICC) 表明所有 SICF 峰值（ICC 范围从 0.73 到 0.79）的会话之间的重测可靠性良好。SICF 在个体中达到最大时的 ISI 在两个实验阶段的所有三个峰值上都是一致的。结果显示，当使用标准配对脉冲协议测量 SICF 时，SICF 在所有三个峰值处的重测可靠性良好。这一发现表明，配对脉冲 TMS 可用于可靠地探测产生 SICF 的神经元间回路的兴奋性。