Curtin Adrian, Tong Shanbao, Sun Junfeng, Wang Jijun, Onaral Banu, Ayaz Hasan
Drexel University, School of Biomedical Engineering, Science and Health Systems, Philadelphia, PA, United States.
School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China.
Front Neurosci. 2019 Feb 28;13:84. doi: 10.3389/fnins.2019.00084. eCollection 2019.
The capacity for TMS to elicit neural activity and manipulate cortical excitability has created significant expectation regarding its use in both cognitive and clinical neuroscience. However, the absence of an ability to quantify stimulation effects, particularly outside of the motor cortex, has led clinicians and researchers to pair noninvasive brain stimulation with noninvasive neuroimaging techniques. fNIRS, as an optical and wearable neuroimaging technique, is an ideal candidate for integrated use with TMS. Together, TMS+fNIRS may offer a hybrid alternative to "blind" stimulation to assess NIBS in therapy and research. In this systematic review, the current body of research into the transient and prolonged effects of TMS on fNIRS-based cortical hemodynamic measures while at rest and during tasks are discussed. Additionally, studies investigating the relation of fNIRS to measures of cortical excitability as produced by TMS-evoked Motor-Evoked-Potential (MEP) are evaluated. The aim of this review is to outline the integrated use of TMS+fNIRS and consolidate findings related to use of fNIRS to monitor changes attributed to TMS and the relationship of fNIRS to cortical excitability itself. Key terms were searched in PubMed and Web-of-Science to identify studies investigating the use of both fNIRS and TMS. Works from Google-Scholar and referenced works in identified papers were also assessed for relevance. All published experimental studies using both fNIRS and TMS techniques in the study methodology were included. A combined literature search of neuroimaging and neurostimulation studies identified 53 papers detailing the joint use of fNIRS and TMS. 22/53 investigated the immediate effects of TMS at rest in the DLPFC and M1 as measured by fNIRS. 21/22 studies reported a significant effect in [HbO] for 40/54 stimulation conditions with 14 resulting an increase and 26 in a decrease. While 15/22 studies also reported [HbR], only 5/37 conditions were significant. Task effects of fNIRS+TMS were detailed in 16 studies, including 10 with clinical populations. Most studies only reported significant changes in [HbO] related measures. Studies comparing fNIRS to changes in MEP-measured cortical excitability suggest that fNIRS measures may be spatially more diffuse but share similar traits. This review summarizes the progress in the development of this emerging hybrid neuroimaging & neurostimulation methodology and its applications. Despite encouraging progress and novel applications, a lack of replicated works, along with highly disparate methodological approaches, highlight the need for further controlled studies. Interpretation of current research directions, technical challenges of TMS+fNIRS, and recommendations regarding future works are discussed.
重复经颅磁刺激（TMS）引发神经活动及操纵皮质兴奋性的能力，引发了人们对其在认知神经科学和临床神经科学应用的巨大期待。然而，由于缺乏量化刺激效果的能力，尤其是在运动皮质之外，临床医生和研究人员已将非侵入性脑刺激与非侵入性神经成像技术相结合。功能近红外光谱技术（fNIRS）作为一种光学且可穿戴的神经成像技术，是与TMS联合使用的理想选择。TMS与fNIRS相结合，可能为“盲目”刺激提供一种混合替代方法，以在治疗和研究中评估非侵入性脑刺激（NIBS）。在本系统评价中，讨论了当前关于TMS对静息及任务期间基于fNIRS的皮质血流动力学测量的瞬时和长期影响的研究。此外，还评估了研究fNIRS与TMS诱发运动诱发电位（MEP）所产生的皮质兴奋性测量指标之间关系的研究。本综述的目的是概述TMS与fNIRS的联合应用，并整合与使用fNIRS监测TMS引起的变化以及fNIRS与皮质兴奋性本身的关系相关的研究结果。在PubMed和科学网中搜索关键词，以识别研究fNIRS和TMS联合应用的研究。还评估了谷歌学术搜索中的文献以及已识别论文中的参考文献的相关性。所有在研究方法中同时使用fNIRS和TMS技术的已发表实验研究均被纳入。对神经成像和神经刺激研究进行的综合文献检索，共识别出53篇详细描述fNIRS与TMS联合应用的论文。其中22/53项研究调查了TMS在静息状态下对背外侧前额叶皮质（DLPFC）和初级运动皮质（M1）的即时影响，通过fNIRS进行测量。21/22项研究报告称，在54次刺激条件中的40次下，氧合血红蛋白（[HbO]）有显著变化，其中14次增加，26次减少。虽然15/22项研究也报告了脱氧血红蛋白（[HbR]），但只有5/37次条件有显著变化。16项研究详细阐述了fNIRS + TMS的任务效应，其中10项涉及临床人群。大多数研究仅报告了与[HbO]相关测量指标的显著变化。将fNIRS与MEP测量的皮质兴奋性变化进行比较的研究表明，fNIRS测量可能在空间上更分散，但具有相似特征。本综述总结了这种新兴的混合神经成像与神经刺激方法学发展及其应用方面的进展。尽管取得了令人鼓舞的进展和有新颖的应用，但缺乏重复研究以及方法学方法差异极大，凸显了进一步进行对照研究的必要性。文中还讨论了对当前研究方向的解读、TMS + fNIRS的技术挑战以及对未来研究工作的建议。
