Thong Sophie, Doery Elizabeth, Biabani Mana, Rogasch Nigel C, Chong Trevor T-J, Hendrikse Joshua, Coxon James P
School of Psychological Sciences and Turner Institute for Brain and Mental Health, Monash University, Melbourne, 3800 Victoria, Australia.
Department of Health, School of Psychology, Deakin University, Melbourne, 3125 Victoria, Australia.
J Neurosci. 2025 Feb 19;45(8):e0443242024. doi: 10.1523/JNEUROSCI.0443-24.2024.
Secondary motor cortical regions, such as the supplementary motor area (SMA), are involved in planning and learning motor sequences; however, the neurophysiological mechanisms across these secondary cortical networks remain poorly understood. In the primary motor cortex, changes in excitatory and inhibitory neurotransmission (: balance) accompany motor sequence learning. In particular, there is an early reduction in inhibition (i.e., disinhibition). Here, we investigated whether disinhibition occurs across secondary motor cortical regions during motor sequence learning using combined transcranial magnetic stimulation (TMS) and electroencephalography (EEG). Twenty-nine healthy adults (14 female) practiced a sequential motor task with TMS applied to the SMA during sequence planning. TMS-evoked potentials (TEPs) were measured with EEG before, during, and after practice. The N45 TEP peak was our primary measure of disinhibition, while we analyzed the slope of aperiodic EEG activity as an additional : balance measure. We observed a reduction in N45 amplitudes across an electrode cluster encompassing the SMA and nearby cortical regions as participants began learning new motor sequences, compared with a baseline rest phase (< 0.01). Smaller N45 amplitudes during early learning were associated with improvements in reaction times across learning (< 0.05). Intriguingly, aperiodic exponents increased as learning progressed and were associated with greater improvements in skill (< 0.05). Overall, our results show that inhibition is modulated across SMA and secondary motor cortex during the planning phase of motor sequence learning and thus provide novel insight on the neurophysiological mechanisms within higher-order motor cortex that accompany new sequence learning.
次级运动皮层区域，如辅助运动区（SMA），参与运动序列的计划和学习；然而，这些次级皮层网络的神经生理机制仍知之甚少。在初级运动皮层中，兴奋性和抑制性神经传递的变化（即平衡）伴随着运动序列学习。特别是，抑制作用会早期降低（即去抑制）。在这里，我们使用经颅磁刺激（TMS）和脑电图（EEG）相结合的方法，研究了在运动序列学习过程中，次级运动皮层区域是否会发生去抑制现象。29名健康成年人（14名女性）在序列计划期间对SMA施加TMS，练习一项连续运动任务。在练习前、练习期间和练习后，用EEG测量TMS诱发的电位（TEP）。N45 TEP峰值是我们去抑制的主要测量指标，同时我们分析了非周期性EEG活动的斜率作为额外的平衡测量指标。与基线休息阶段相比，当参与者开始学习新的运动序列时，我们观察到在包括SMA和附近皮层区域的电极簇上N45振幅降低（<0.01）。早期学习期间较小的N45振幅与学习过程中反应时间的改善相关（<0.05）。有趣的是，随着学习的进行，非周期性指数增加，并且与技能的更大改善相关（<0.05）。总体而言，我们的结果表明，在运动序列学习的计划阶段，SMA和次级运动皮层的抑制作用受到调节，从而为伴随新序列学习的高阶运动皮层内的神经生理机制提供了新的见解。
