Sriutaisuk Napat, Franz Elizabeth A
Action Brain and Cognition Lab, Department of Psychology, University of Otago, Dunedin, New Zealand.
William James Building, 4th Floor 412, Psychology, 275 Leith Walk, Dunedin, 9016, New Zealand.
Exp Brain Res. 2025 May 4;243(6):134. doi: 10.1007/s00221-025-07091-y.
Motor skill learning plays a crucial role in human functioning and is often studied using transcranial magnetic stimulation (TMS) to assess corticospinal excitability (CSE). CSE, which reflects the motor system's responsiveness, is compared across experimental conditions to determine whether a factor facilitates or inhibits motor skill learning. However, variability in stimulation predictability may confound interpretation of CSE measures. In this study, we examined the impact of TMS predictability on CSE by comparing motor-evoked potential (MEP) responses under predictable and unpredictable conditions. Twenty right-handed participants underwent TMS-EMG recordings while observing either a predictable visual cue (a moving white bar) or an unpredictable visual cue (a static white bar). MEP amplitudes were recorded from the first dorsal interosseous (FDI) muscle and normalized across participants. Results showed that unpredictable TMS produced significantly larger MEP amplitudes compared to predictable stimulation. The findings suggest that the predictability of TMS substantially modulates CSE, potentially confounding the results in previous TMS studies on action observation and motor facilitation. Ensuring consistent stimulation predictability across experimental conditions is therefore essential for accurately interpreting TMS-induced CSE changes.
运动技能学习在人类机能中起着至关重要的作用，并且经常使用经颅磁刺激（TMS）来研究，以评估皮质脊髓兴奋性（CSE）。CSE反映了运动系统的反应性，在不同实验条件下对其进行比较，以确定某个因素是促进还是抑制运动技能学习。然而，刺激可预测性的变化可能会混淆对CSE测量结果的解释。在本研究中，我们通过比较可预测和不可预测条件下的运动诱发电位（MEP）反应，研究了TMS可预测性对CSE的影响。20名右利手参与者在观察可预测视觉线索（移动的白色条）或不可预测视觉线索（静态白色条）时接受了TMS-EMG记录。从第一背侧骨间肌（FDI）记录MEP振幅，并在参与者之间进行标准化。结果表明，与可预测刺激相比，不可预测的TMS产生的MEP振幅明显更大。研究结果表明，TMS的可预测性会显著调节CSE，这可能会混淆先前关于动作观察和运动促进的TMS研究结果。因此，确保不同实验条件下刺激可预测性的一致性对于准确解释TMS诱导的CSE变化至关重要。
