Black Garrett S, Dugdale Joshua A, Borrell Jordan A
Bioengineering Program, University of Kansas, Lawrence, KS, United States of America.
Department of Occupational Therapy Education, University of Kansas Medical Center, Kansas City, KS, United States of America.
J Neural Eng. 2025 Sep 1;22(5). doi: 10.1088/1741-2552/adfd8b.
Functional near-infrared spectroscopy (fNIRS) has emerged as a promising brain imaging tool due to its cost-effectiveness and balance between spatial and temporal resolution. However, its reliance on the 10-20 EEG coordinate system for probe placement introduces potential inaccuracies in cortical localization. Despite concerns regarding its spatial precision, the integration of transcranial magnetic stimulation (TMS) with fNIRS for validating signal localization has not been systematically explored. This study aimed to demonstrate the interindividual variability in hand motor representations and how it influences the precision of fNIRS recordings during motor tasks.Neuronavigated TMS was employed on 18 neurotypical adults to map the motor representations of the first dorsal interosseous (FDI) and fourth dorsal interosseous (4DI) muscles. Center-of-gravity (CoG) coordinates from TMS-evoked motor maps were compared with fNIRS channel locations, including the theoretical hand channel defined by the 10-20 EEG system. FNIRS signals were recorded during a hand-grasp motor task, and the subject-specific hand channel was determined by identifying the fNIRS channel closest to the individual's TMS CoG.TMS motor mapping revealed substantial interindividual variability, with 56% of participants demonstrating deviations from the theoretical fNIRS hand channel. TMS motor maps showed that the FDI and 4DI representations were closely positioned, with the 4DI representation slightly anterior to the FDI (= 0.022). Analysis of fNIRS signals indicated that subject-specific hand channels exhibited significantly higher hemodynamic response amplitudes compared to the theoretical hand channel (= 0.0004), suggesting enhanced signal sensitivity when using individualized cortical mapping. Additionally, fNIRS signal variance was significantly higher in the theoretical channel, indicating greater signal variability and lower signal robustness.These findings highlight the limitations of rigidly applying the 10-20 EEG system for spatial localization in fNIRS-based motor studies and show the benefits of integrating TMS-derived cortical mapping for improved signal accuracy and robustness.
功能近红外光谱技术（fNIRS）因其成本效益以及空间和时间分辨率之间的平衡，已成为一种很有前景的脑成像工具。然而，它在探头放置时依赖10-20脑电图坐标系统，这在皮质定位中会引入潜在的不准确性。尽管对其空间精度存在担忧，但尚未系统地探索将经颅磁刺激（TMS）与fNIRS整合以验证信号定位的情况。本研究旨在证明手部运动表征的个体间变异性，以及它如何影响运动任务期间fNIRS记录的精度。
对18名神经典型成年人采用神经导航TMS来绘制第一背侧骨间肌（FDI）和第四背侧骨间肌（4DI）的运动表征。将TMS诱发运动图谱的重心（CoG）坐标与fNIRS通道位置进行比较，包括由10-20脑电图系统定义的理论手部通道。在手部抓握运动任务期间记录fNIRS信号，并通过确定最接近个体TMS CoG的fNIRS通道来确定个体特定的手部通道。
TMS运动图谱显示出显著的个体间变异性，56%的参与者表现出与理论fNIRS手部通道的偏差。TMS运动图谱表明，FDI和4DI表征位置紧密，4DI表征略位于FDI前方（= 0.022）。fNIRS信号分析表明，与理论手部通道相比，个体特定的手部通道表现出显著更高的血流动力学反应幅度（= 0.0004），这表明使用个性化皮质图谱时信号敏感性增强。此外，理论通道中的fNIRS信号方差显著更高，表明信号变异性更大且信号稳健性更低。
这些发现突出了在基于fNIRS的运动研究中严格应用10-20脑电图系统进行空间定位的局限性，并显示了整合TMS衍生的皮质图谱以提高信号准确性和稳健性的好处。
