Name: simultaneous transcranial alternating current stimulation and functional magnetic resonance imaging
Uploaded: 2017-06-05T14:00:00.000+00:00
Duration: 10 min 25 s
Description: Watch this Scientific Journal Video about Simultaneous Transcranial Alternating Current Stimulation and Functional Magnetic Resonance Imaging at JoVE.com

我们感谢Ilona Pfahlert和Britta Perl在功能成像实验期间的技术帮助，SeverinHeumüller提供卓越的电脑支持。这项工作得到了Herman和Lilly Schilling基金会以及大脑纳米显微镜和分子生理学中心（CNMPB）的支持。

根据制度伦理委员会的指导方针进行所有实验。对于本手稿中提到的所有研究，所有程序均按照赫尔辛基的声明进行，并由哥伦比亚大学医学中心的当地伦理委员会批准。 实验前的刺激和计算机设置<ol><li> 刺激仪设置 注意:用于该fMRI实验的刺激器是专门设计的磁共振（MR）兼容系统，配备有MR安全内滤芯，外滤芯，安全电阻，耦合电缆和MR安全材料。一些说明专门针对制造商的指示，并且在使用另一个刺激器时可能有所不同，因此请注意遵循制造商提供的可能构成此设置例外的设备说明。 图1A显示了刺激器在这个实验设置中使用的组件。 <ol><li>浏览刺激器的菜单以编程所需的实验参数（有关详细信息，请参阅用户手册）。例如，对于10Hz的刺激频率，程序10的周期为1s的上升/下降时间，30秒的刺激为300次正弦周期，等于1,000μA的电流强度以及重复的触发模式除非另有说明。每次实验运行后，保存程序加载。 </li><li>使用BNC电缆将刺激演示计算机触发输出连接到刺激器。 </li><li>通过射频（RF）波导管从扫描仪室内放置非磁性屏蔽局域网（LAN）电缆。为了避免谐振电容耦合，请确保电缆没有环路并沿着房间的墙壁放置，通向磁体孔的后部并沿着右侧的扫描仪床轨孔内，导致内部过滤箱的位置（参见图1C和步骤2.4中关于电缆位置的安全说明）。用长度间断放置的胶带固定电缆。 </li></ol></li><li>将视觉刺激程序加载到与扫描仪控制计算机分离的指定演示计算机上。 如图1C所示，将演示计算机通过光电转换器连接到扫描仪触发输出，并将其放置在放置在屏蔽盒中或磁体室外部的输出设备（ 即投影仪）上。使用非磁性镜将投影引导到扫描仪孔内的屏幕上。 </li></ol>主题到达和准备<ol><li>用于MR扫描的任何禁忌症的预筛选受试者（ 例如 ，没有金属植入物，无幽闭恐惧症，实验特异性受试者先决条件）为以及tACS（ 例如 ，癫痫史，慢性头痛，怀孕） 26,27 。 </li><li>当受试者到达时，指导受试者关于fMRI实验细节并描述预期的经验（ 例如 ，来自tACS的视觉刺激，刺痛或脊椎动物，特殊任务说明）。 </li><li> 根据10-20脑电图放置电极和刺激剂制备。 <ol><li>使用卷尺，测量被检者的头部从鼻子到头部的距离，以及头部顶部的耳朵到耳朵的距离。根据10-20脑电图系统，两个长度的交点给出了头上的位置。使用标记标记头皮上的Cz的斑点。 </li><li>将无电极的EEG帽放置在受试者的头部上，Cz与对象头皮上的标记对齐，确定电极的所需位置并标记它们。 不E:重要的是，所有实验者都使用相同的放置系统来确保所有实验的一致性;通常用于经颅刺激实验的10-20脑电图系统具有保持精确电极放置26,28的具体指导。 </li><li>使用酒精和棉垫，清洁受试者头皮上标记斑点周围的头发和皮肤;去除油和头发产品。 </li><li>在橡胶电极上涂抹一些凝胶，并将每个电极牢固地压在被检者头皮上标记和清洁的位置上，确保电极与导电胶完全接触，同时具有最小的阻抗。 </li><li>使用备用屏蔽LAN电缆，将滤波器盒和MR安全电缆连接到刺激器和橡胶电极， 如图1A所示 。 </li><li>打开刺激器并测试阻抗（参考用户的手册了解详情）。如果阻抗不低于20kΩ，请按照头皮上的电极或根据需要添加电极凝胶，直到达到该阻抗指标。 </li><li>当阻抗低于20kΩ时，允许刺激器输出电流几秒钟，以使受试者感觉到感觉体验。在这次测试期间询问关于感觉知觉的问题，包括是否存在刺痛感和可以忍受的刺痛感，以及在刺激期间磷虾的程度或位置。 </li><li>此时，主体准备移动到扫描仪床。将电极电缆插入主体上的橡胶电极，断开刺激器，备用LAN电缆以及外部和内部过滤器盒。 </li><li>将外部过滤器盒连接到穿过波导的LAN电缆到MR扫描仪，尽可能少的露出的LAN电缆在波导外部（ 见图1B ）。连接刺激器使用刺激电缆到外部过滤箱，并仔细检查刺激器是否连接到演示计算机触发输出。 </li></ol></li><li> 准备MR扫描仪内的物体。 注意: 图1C显示了实验期间完整的tACS-fMRI设置。按规定布置电缆和内部过滤箱至关重要，电极电缆与扫描仪床的平面成大约90°的角度，而位于扫描仪右侧的扫描仪床上的内部过滤盒孔。忽视这样做可能会损坏电极电缆的安全电路;该配置适用于开路和闭路RF线圈。 <ol><li>在确保受试者没有磁性材料并准备进行MRI实验后，将受试者导入扫描仪室。 </li><li>给耳塞听力保护，并指导主体说谎在扫描仪床上，将枕头放置在头部和下方，以舒适舒适，并减少运动。将枕头放置在受试者头部后面时，请特别注意在实验期间将电极电缆平放并放置在受试者舒适的位置。 </li><li>给主体提供报警球和MR安全响应按钮盒，使其在实验中按下按钮需要最小的移动。 </li><li>将RF头部线圈固定在受试者头部上，并附上镜子，使得受试者可以看到以正确方向反射的投影屏幕。 </li><li>暂时将来自橡胶电极的电极电缆的自由端固定到头部线圈中的一个位置，使其在床移动时不会卡住。 图1D显示位于头盘中的被摄对象的头部有枕头，镜子和tACS电缆到位b将床移动到中心头线圈进行成像。作为示例，当扫描仪床处于测量位置时，过滤箱也被示出放置在扫描仪床栏杆上，作为其相对于头部线圈位置的示例。 </li><li>将扫描仪床移动到测量位置。从扫描器孔的后端，将电极电缆从橡胶电极连接到连接到LAN电缆的内部过滤器盒， 如图1C所示 。为了防止扫描过程中的过度运动，请用带和沙袋将电缆和过滤箱沿着扫描仪床栏杆固定在孔的右侧。将投影机屏幕放入扫描仪孔的后端。 </li><li>再次测试刺激器上的阻抗，以确保电缆，过滤器盒和刺激器之间的所有连接正确。 </li></ol></li></ol> 3.扫描和实验<ol><li>在扫描开始之前，先测试一下演示计算机在主体按下响应按钮时进行注册。 </li><li> 获取高分辨率T1加权解剖数据（ 例如 ，三维涡轮快速低角度镜头，回波时间（TE）:3.26 ms，重复时间（TR）:2,250 ms，反转时间:900 ms，翻转角9°，各向同性分辨率为1×1×1mm 3 ）。 <ol><li>在采集之后，将解剖MRI上的对比度和窗口调整到低极限和高极限，以在扫描期间目视检测可能由刺激器设置引起的噪声。在功能图像采集的同时，继续对噪声进行视觉监控。 </li></ol></li><li>在演示计算机上开始实验，准备开始扫描仪触发，并启动刺激器等待演示计算机输出触发。在整个fMRI实验中保持刺激器并连接，以避免刺激器之间的时间信噪比（tSNR）的差异开启和关闭条件22 。 </li><li>开始fMRI扫描（ 例如 ，二维T2 *加权梯度回波回波平面成像; TE:30 ms，TR:2,000 ms，翻转角70°，3 mm厚度的33片，切片之间没有间隙3 x 3 mm 2的平面内分辨率，扫描7分钟的210卷），这将在演示计算机上触发实验的开始。监视刺激器显示，以确保在实验运行期间在所需时间发送电流。 </li></ol>实验结论<ol><li>实验完成后，扫描完成后，在移动扫描仪床之前，从连接橡胶电极的电缆拔下内部过滤盒，从扫描仪上取出物体，取出电极，使被摄体自由洗净头发。 </li><li>关闭刺激器，并将其插入充电。用水清洗橡胶电极t使用。 </li></ol>

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B., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Connectivity+and+functional+profiling+of+abnormal+brain+structures+in+pedophilia.">Connectivity and functional profiling of abnormal brain structures in pedophilia.</a> Hum Brain Mapp. 36 (6), 2374-2386 (2015).</li><li>Cabral-Calderin, Y., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcranial+Alternating+Current+Stimulation+Affects+the+BOLD+Signal+in+a+Frequency+and+Task-dependent+Manner.">Transcranial Alternating Current Stimulation Affects the BOLD Signal in a Frequency and Task-dependent Manner.</a> Human Brain Mapping. 37 (1), 94-121 (2016).</li><li>Antal, A., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+artifacts+induced+by+electrical+stimulation+during+conventional+fMRI+of+the+brain.">Imaging artifacts induced by electrical stimulation during conventional fMRI of the brain.</a> Neuroimage. 85 (Pt 3), 1040-1047 (2014).</li><li>Turi, Z., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Both+the+cutaneous+sensation+and+phosphene+perception+are+modulated+in+a+frequency-specific+manner+during+transcranial+alternating+current+stimulation.">Both the cutaneous sensation and phosphene perception are modulated in a frequency-specific manner during transcranial alternating current stimulation.</a> Restor Neurol Neurosci. 31 (3), 275-285 (2013).</li><li>Kanai, R., Paulus, W., Walsh, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcranial+alternating+current+stimulation+(tACS)+modulates+cortical+excitability+as+assessed+by+TMS-induced+phosphene+thresholds.">Transcranial alternating current stimulation (tACS) modulates cortical excitability as assessed by TMS-induced phosphene thresholds.</a> Clinical Neurophysiology. 121 (9), 1551-1554 (2010).</li><li>Schutter, D. J., Hortensius, R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Retinal+origin+of+phosphenes+to+transcranial+alternating+current+stimulation.">Retinal origin of phosphenes to transcranial alternating current stimulation.</a> Clinical Neurophysiology. 121 (7), 1080-1084 (2010).</li><li>Witkowski, M., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Mapping+entrained+brain+oscillations+during+transcranial+alternating+current+stimulation+(tACS).">Mapping entrained brain oscillations during transcranial alternating current stimulation (tACS).</a> Neuroimage. , (2015).</li><li>Vossen, A., Gross, J., Thut, G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Alpha+Power+Increase+After+Transcranial+Alternating+Current+Stimulation+at+Alpha+Frequency+(alpha-tACS)+Reflects+Plastic+Changes+Rather+Than+Entrainment.">Alpha Power Increase After Transcranial Alternating Current Stimulation at Alpha Frequency (alpha-tACS) Reflects Plastic Changes Rather Than Entrainment.</a> Brain Stimul. 8 (3), 499-508 (2015).</li><li>Alekseichuk, I., Diers, K., Paulus, W., Antal, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Transcranial+electrical+stimulation+of+the+occipital+cortex+during+visual+perception+modifies+the+magnitude+of+BOLD+activity:+A+combined+tES-fMRI+approach.">Transcranial electrical stimulation of the occipital cortex during visual perception modifies the magnitude of BOLD activity: A combined tES-fMRI approach.</a> Neuroimage. , (2015).</li></ol>

作者没有什么可以披露的。

在这里，我们描述了使用MR兼容的tACS系统同时进行tACS-fMRI实验设置和执行的过程。该过程中的一些步骤需要特别注意，特别是关于主题设置。本实验中使用的MR兼容刺激器和设置仅在电缆，滤波器和电极上具有约12kΩ的最小阻抗，制造商建议使用电极连接到被摄体的20kΩ最小阻抗;这个要求取决于刺激产品和制造商。当向受试者施加电极时，如果阻抗太高，则除了按压电极之外，可以采取一些步骤来减小该值。例如，在将电极压在头皮上之前，首先用包括毛发在内的电极凝胶覆盖头皮上的标记和清洁的位置可能更容易。这将确保电流分布在非导电材料上;然而，注意将电极凝胶覆盖度限制在与电极大致相同的表面积，以将电流扩散到所需的刺激区域。如果电极靠近在一起，由于电极之间的电流分流可能通过多余的电极凝胶接触而发生，因此要特别注意。如果电极位于头部背面，受试者将直接放置在其上，必须特别注意将枕头放在头后面，使得受试者不会随着实验的进行而变得不舒服;这种不适可能不是最初的问题的问题，但是经验表明痛苦随着时间的推移而增加。此外，与所有fMRI实验一样，受试者运动引起了有问题的混淆，因此重要的是该对象对所有的电缆和电极都适合使用。 要考虑的设置的最重要的方面是可能引入的噪声到可以引起图像伪像和失真的MR环境。在实验之前，使用整个tACS设置来测试图像伪影是谨慎的。可以使用正常的球形体模，用电极凝胶固定电极。提供电流在电极之间行进的一些方法是重要的，这可以通过在从一个电极到另一个电极的路径中施加大量的电极凝胶来实现。按照计划进行整个实验，包括频率和电流等参数变化。在扫描会话期间，在MR扫描仪控制计算机上的图像查看器中将对比度和窗口调整到极限值可以更容易地进行视觉检测。当在实验之前和实验期间可视地监测噪声时，作为示例，噪声可能发生在具有高强度的图像中的尖峰，不应该测量信号的模式或随时间变化的强度。用RF激励获取fMRI数据关闭n个脉冲，在扫描期间提供有关扫描仪环境噪声的信息，而无需获取实际的图像信号（ 见图2 ）。这种噪声测试可以在每次扫描会话中完成。如果噪音有变化，请检查所有电缆是否完好无损，并且与刺激器，电极和过滤器盒连接良好。没有电缆应该环绕。噪声或变形可能源于电缆断裂，橡胶中有金属污染物的电极（尽管出售为MR兼容），以及其他可能的故障连接。刺激器是电池驱动的，以最小化设置中的电噪声;确保在每次实验之前充分充电，并在整个实验中保持连接。功能图像中的TSNR将在刺激器连接的情况下降低约5％，然而，值应在刺激条件下稳定22 。同时经颅电刺激 - fMRI测试on个尸体已经表明，没有与交流电刺激相关的伪像，这与直流电刺激相比是一个优势30 。从理论上说，这种缺乏伪像可以通过图像采集时的净电流为零来解释30 。然而，对于我们实验室进行的一些实验，采集时间或TR不是刺激频率的倍数。在进行本协议中提到的噪声测试并检查不可见的人为因素的图像之后，我们得出结论，净电流与零点的任何差异都很小，也可忽略不计，从而导致伪影。 成功实验的另一个关键点是演示计算机接收扫描仪的触发输出，并且刺激器从演示计算机接收触发器。在实验之前，使用th进行视觉刺激设计和时序的编程所需的软件。该程序必须使用触发器将视觉刺激显示与MR扫描仪和刺激器同步;它以从MR扫描仪输出的触发信号启动，并且在所需的刺激时间内将输出触发信号发送到刺激器。在设置期间检查触发通信的简单方法是使用附带BNC电缆的示波器将扫描仪触发输出以及演示计算机输出。在我们的设置中，MR扫描仪为所获取的每个功能音量输出触发（切换），演示计算机通过演示软件输入信号。精心设计的实验的分析主要依靠适时的刺激。 本实验的一些步骤可能需要进行实验室设置要求的调整。例如，这个设置描述了使用投影仪和镜子进行视觉刺激呈现，然而视觉刺激方式输入装置可以是基于实验和实验室偏好或限制选择的MR安全液晶显示护目镜或MR安全监视器。此外，MRI扫描参数应适合实验。值得注意的是，应该注意适当选择tACS的实验控制，尽管不存在直接的答案。 30秒的短暂的假手术刺激可以模拟由tACS诱导的体细胞增生，其最终在延长的刺激下减少;然而，一些研究表明，甚至短时间的刺激可以诱导振荡夹带12 。可用于tACS的另一个可能的控制是使用非有效频率，或换句话说，与感兴趣的频率不同的频率来刺激。这里的例外情况是，生长激素和磷光体感知根据刺激频率31而变化。最后，关于刺激的主观经验因此，为了最佳地捕获受试者的变异性，考虑使用详细的评估系统进行磷光感知，并花费一些时间与受试者描述磷光体的各种特征（ 如位置，强度）可以出现，使受试者可以在刺激期间仔细评估他或她的经验32,33 。 这里显示的代表性结果表明，tACS效应是电流依赖性的，频率依赖性的，并且该调制不限于电极下方的区域，而是延伸到可能的功能连接区域。该技术的一个限制是fMRI以及BOLD响应的时间分辨率。数据采集​​和血液动力学反应不如脑的刺激频率或电活动那么快，所以与频率的直接相互作用tACS的特异性效应无法测量。然而，考虑到tACS效应的科学文献的最大份额是行为研究，并且tACS显着影响整个复杂的神经系统，很明显，同时tACS-fMRI实验可以提供给我们关于tACS效应的信息大脑。 EEG和MEG提供了与神经活动相匹配的时间分辨率水平的见解。然而，EEG和MEG受到空间分辨率和皮质深度限制或计算密集型源重建技术的困扰。在相同频率下记录的兴奋的脑信号的刺激频率和谐波伪影进一步使EEG和MEG分析复杂化。创新的解决方法已被应用于解决其中的一些挑战。 Helfrich等人采用了一种新技术，使用伪像模板减法和主成分分析来从EEG数据中去除tACS伪影15 </s了&gt;。他们表明，10 Hz tACS应用于枕叶枕骨上增加了顶叶和枕叶皮质中的α活性，并诱导在相似固有频率下起作用的皮质振荡器中的同步。 Witkowski及其同事应用幅度调制tACS，并成功构建了夹带脑震荡的基于MEG的皮质图。为了更好地理解正常和异常的大脑功能，最终临床诊断或治疗应用tACS，目标是将tACS应用于脑电图，脑电图和功能磁共振成像，以互补建立可定制的特定期望效果的最佳实践专门针对个人。当建立这种做法时，可以进行有效的调查，以更好地了解神经振荡的功能（ 例如 ，明确定义不同频带的功能角色和关系）及其与tACS的调制（例如，机制是否通过夹带或塑性变化而发生35 ）。 考虑到未来的发展方向，这里描述的设置适用于研究感知或认知的功能磁共振成像实验，如这里描述的运动结构研究和其他研究所所展示的。 Cabral-Calderin及其同事表明，枕视皮质区域的激活取决于视频观察与手指敲击实验22中的任务和tACS频率。在同时进行的tACS静息状态下的fMRI研究中，Cabral-Calderin及其同事显示tACS对内在功能连接和静息状态网络的频率依赖性影响。 Vosskuhl 等人组合tACS和功能磁共振成像在单个α频率刺激下的视觉警戒任务期间显示BOLD降低24 。 Alekseichuk及其同事表示，即时后遗症10Hz tACS在方格环和楔形物的视觉感知期间调制BOLD信号，表明被动感知任务36的神经代谢的变化。这些研究为同时进行的tACS-fMRI研究设定了探索从代谢到认知的许多水平的功能机制的阶段。在使用tACS进行翻译研究的这种早期阶段，同时进行tACS-fMRI实验有可能增加对刺激技术和振荡对认知功能的贡献的理解。

经颅交感刺激（tACS）是一种非侵入性的脑刺激技术，有望在健康人群中调查神经振荡和频率特异性脑功能，并研究和调节临床人群的振荡1 。使用放置在头皮上的两个或多个导电电极，将低电流（1-2mA峰 - 峰）正弦波以期望的频率施加到脑，以与正在进行的神经振荡相互作用。 TACS研究已经测量了频率和任务特定的行为或认知调节，包括但不限于运动功能2 ，工作记忆性能3 ，躯体功能障碍4和视觉感知5,6,7 。以非侵入性方式应用交流电流也导致功能改善神经系统的患者，如帕金森氏症的震颤减少8 ，改善视神经病变9 ，提高卒中后的言语，感觉和运动恢复率10 。尽管越来越多的研究使用tACS进行研究，并证明其在临床环境中的治疗潜力，但是这种技术的效果并没有被充分表征，其机制尚未完全明了。 模拟和动物研究可以在控制条件11,12的细胞或神经网络水平下提供交流电刺激的影响，但鉴于有效刺激技术13,14的状态依赖性，这些研究并没有揭示整个图像。结合tACS与神经成像技术例如脑电图（EEG） 15,16,17 ，脑电图（MEG） 18,19,20或功能磁共振成像（fMRI）21,22,23,24可以通知脑功能的系统级调制。然而，每种组合都带来技术挑战，主要是由于感兴趣的频率测量中的刺激引起的伪影15 。虽然fMRI的时间分辨率不能匹配脑电图或MEG测量，但其在皮质和皮质下脑区域的空间覆盖和分辨率是优越的。 最近，在组合的tACS-fMRI研究中，我们显示tACS对血氧饱和度的影响d用fMRI测量的后验（BOLD）信号是频率和任务特定的，并且刺激不一定直接在电极下方发挥其最大的效果，而是在远离电极22的区域中 。在下面的研究中，我们调查了tACS电极位置和频率对网络功能的影响，使用低频波动和休眠状态功能连通性的幅度，包括使用最直接刺激区域的相关种子，从基于主题的电流密度模拟。在本研究中最为显着的是，α（10Hz）和γ（40Hz）刺激通常在网络连接或区域调制中引起相反的影响。另外，最受影响的休息状态网络是左前额叶控制网络。这些研究强调了使用功能磁共振成像确定最佳参数的潜力mulation。此外，它们有助于证明，除了受控参数，如任务条件和时间，刺激频率和电极位置之外，还存在影响tACS成功的受试者特异性因素。在优化刺激参数中转化为不可控变量的主题特征的例子是内在功能连接性，内源性振荡峰值频率（ 例如 ，单个α频率）以及颅骨和皮肤厚度25 。考虑到目前关于tACS的文献，需要更多的研究结合tACS与神经影像学等神经测量，以建立有效的脑刺激技术的综合程序。 在这里，我们描述了一个安全可靠的设计，用于与视觉任务的fMRI同时应用tACS的实验，重点放在成功同步tAC的设置和执行方面S具有无伪影的fMRI数据采集。

<table><tbody><tr><td>None</td><td></td><td></td><td></td></tr><tr><td>DC-Stimulator MR</td><td>NeuroConn, Ilmenau, Germany</td><td></td><td>includes: inner filter box, outer filter box, MR-safe electrode and stimulator cables (1 each), stimulator, 2 surface electrodes, and one shielded LAN cable; NOTE: This manuscript describes tACS-fMRI setup with NeuroConn&#039;s MR-safe stimulator, but such a stimulator from another manufacturer would be acceptable, with adaptations made based on manufacturer specifications.</td></tr><tr><td>3 tesla Tim Trio MR scanner</td><td>Siemens, Erlangen, Germany</td><td></td><td></td></tr><tr><td>presentation computer</td><td></td><td></td><td></td></tr><tr><td>presentation software (&lt;em&gt;e.g.&lt;/em&gt;;, Matlab)</td><td>The Mathworks, Natick, USA</td><td></td><td></td></tr><tr><td>shielded LAN cable</td><td></td><td></td><td></td></tr><tr><td>projector</td><td>InFocus Corporation, Wilsonville, USA</td><td>IN-5108</td><td></td></tr><tr><td>Ten20 Electrode Paste</td><td>Weaver and Co., Aurora, USA</td><td></td><td></td></tr><tr><td>EEG cap - EASYCAP 32-channel system</td><td>Brain Products GmbH, Germany</td><td></td><td></td></tr><tr><td>tape measure</td><td></td><td></td><td></td></tr><tr><td>marker</td><td></td><td></td><td></td></tr><tr><td>pillows</td><td></td><td></td><td></td></tr><tr><td>button response box</td><td>Current Designs, Philadelphia, USA</td><td></td><td></td></tr><tr><td>isopropyl alcohol</td><td></td><td></td><td></td></tr><tr><td>cotton pads</td><td></td><td></td><td></td></tr><tr><td>tape</td><td></td><td></td><td></td></tr><tr><td>MR-safe sand bags</td><td>Siemens, Erlangen, Germany</td><td></td><td></td></tr><tr><td>MR-safe mirrors</td><td>Siemens, Erlangen, Germany</td><td></td><td></td></tr><tr><td>MR-safe screen</td><td></td><td></td><td>can be built in local machine shop to fit site-specific parameters</td></tr><tr><td>E-A-Rsoft ear plugs</td><td>3M, Bracknell, UK</td><td></td><td></td></tr></tbody></table>

simultaneous transcranial alternating current stimulation and functional magnetic resonance imaging

经颅交流刺激（tACS）是脑振荡无创检测的有前景的工具。 TACS通过用表面电极施加到头皮上的电流对人脑进行频率特异性刺激。最新的技术知识是基于行为研究;因此，将该方法与脑成像结合起来有可能更好地了解tACS的机制。由于电气和敏感性伪影，将tACS与脑成像结合可能是具有挑战性的，然而，一种非常适合与tACS同时使用的脑成像技术是功能性磁共振成像（fMRI）。在我们的实验室，我们已经成功地将tACS与fMRI同步测量结合在一起，以表明tACS效应是状态，电流和频率依赖性的，脑活动的调节不限于电极正下方的区域。本文介绍了一个安全可靠的集合用于与视觉任务fMRI研究同时应用tACS，这可以帮助理解振荡脑功能以及tACS对脑的影响。

图2和图3分别示出了在幻影和人类受试者中分别用于设备噪声测试的代表性图像。在每一行中， 图2和图3示出了相应地在行上标记的来自所获取的体积或计算的图的代表性轴向切片。每行上最右边的图像是对应的体积或计算的地图的矢状表示，指示具有蓝线的轴向切片位置。除了第一行，其示出了以白色的电极布置，该体积叠加在每个图中的T1加权图像上。请注意，T1加权图像中的电极没有失真或信号丢失。 图2的第二行示出了使用tACS设置获得的代表性功能性MRI数据并进行了转换上。在图2中的幻影中，注意到由于电极而导致一些信号丢失和失真，然而， 图3的行2显示出这些失真不会延伸到被摄体内的头皮之外。 图2中的第三行和第四列示出了使用与fMRI数据相同的参数而没有RF激励脉冲获取的体积中的噪声测量。图像显示扫描仪室和扫描期间MR硬件的噪声水平。第三行是使用tACS关闭的噪声测量，第四行是使用tACS打开的第四行。在图2的第五行和第六行中，分别使用tACS设置和刺激器关闭和打开的功能运行的tSNR映射。从人类受试者获得的数据中计算出的TSNR图显示在图3中，三个是tACS关闭，四个是tACS。注意没有可见的差异在刺激条件之间进行比较时的强度。正如我们在之前的一项研究中所展示的那样，tACS设备在tSNR下降了约5％，与没有tACS设置的tSNR相比，tSNR在刺激开启和关闭条件22时应保持稳定。 图4表示一系列图像，其演示当使用非MR兼容电极时可能发生的信号丢失。来自可能具有一些金属污染的电极的受试者的fMRI体积的切片显示在大致超过初级运动皮层的电极下方的信号丢失，如红色圆圈所示。 图5显示了测试16 Hz Cz-Oz tACS电流强度对BOLD信号影响的实验结果，<html>问是中枢交叉固定。在整个实验中，12秒的tACS周期交错，非刺激周期从24-32秒变化。以伪随机顺序，在四次运行中，在tACS中施加不同的电流强度（500μA，750μA，1,000μA，1,500μA）。 图5A显示了统计学上显着的簇的BOLD信号的事件相关平均值，随着电流强度增加对BOLD信号的影响增加。另外， 图5B示出了电流强度特异性T分数图，其显示了效应的区域特异性以及随着电流强度增加而增加的空间效应。还值得注意的是，正面区域的BOLD活性发生了显着变化，表明调制并不总是直接位于电极下方。详情请参阅Cabral-Calderin及其同事22 。 e_content"fo:keep-together.within-page ="1"&gt; 图6显示了在视觉感知任务中测试tACS效应的频率依赖性的实验的代表性结果，受试者报告了双稳态旋转球的感知方向，同时，在三个单独的会话中的每一个中，以三个刺激频率（10Hz，60Hz或80Hz）中的一个施加电极置于Cz和Oz的tACS。 图6A示出了视觉呈现和tACS周期之间的实验时间TACS条件和频率效应相互作用图和集群事后检测显示顶叶皮层的频率特异性效应，10 Hz tACS减小和60 Hz增加信号（ 图6B ） 图6C显示T评分60 Hz tACS超出顶叶皮层的特定效果图包括一些枕骨人和地区。有关实验和分析的详细信息，请参阅Cabral-Calderin 等。 22 。 <img alt="图1" class="xfigimg" src="/files/ftp_upload/55866/55866fig1.jpg" /> 图1:扫描仪中的TACS设置。 （ A ）具有所有必要元素的TACS设置。刺激器和电缆连接在MR屏蔽室外。还示出了用于电极放置的EEG帽，卷尺和导电凝胶。 （ B ）外部过滤箱和刺激器放置在扫描仪室外。 LAN电缆（图中不可见）通过RF波导管来自扫描仪室，并连接到外部过滤盒，尽可能少的LAN电缆暴露在扫描仪室外。刺激器应连接到外部过滤盒以及演示计算机触发输出电缆。 （ C ）扫描仪环境与实验设置。描述tACS设置，包括演示计算机，扫描仪和触发输出以及投影机。 （ D ）实验主题定位。重要的元素包括枕头，电缆放置，观察镜和头部线圈。过滤箱放置在扫描仪床栏杆上，作为放置在孔内的示例。 <a href="http://ecsource.jove.com/files/ftp_upload/55866/55866fig1large.jpg" target="_blank">请点击此处查看此图的较大版本。</a> <img alt="图2" class="xfigimg" src="/files/ftp_upload/55866/55866fig2.jpg" /> 图2:获得Phantom的质量评估MR图像。第1行:高分辨率解剖T1加权图像轴向切片，其位置在右侧的矢状切片上由蓝线表示（也可以在每个后续行中看到）。在矢状平面上，电极位置是illust<html>以白色评级行2:T2 *加权的回波平面图像切片，品红色箭头指示由于电极和/或电极凝胶引起的信号丢失和失真。在矢状平面上，相应体积的定位显示为覆盖（也可以在每一行中看到）。第3行:使用fMRI实验参数获取的噪声图像片段，而tACS设置就位并打开但不刺激时，无RF激发脉冲。第4行:使用tACS设置获取无RF激励图像，刺激器开启并以16 Hz激励。第5行:从使用tACS设置获取的数据计算出的TSNR图，并打开，但不刺激。第6行:使用tACS设置获取的数据计算出的TSNR图，并以16 Hz刺激。 <a href="http://ecsource.jove.com/files/ftp_upload/55866/55866fig2large.jpg" target="_blank">请点击此处查看此图的较大版本。</a> 图3"class ="xfigimg"src ="/ files / ftp_upload / 55866 / 55866fig3.jpg"/&gt; 图3:获得主题的质量评估MR图像。第1行:高分辨率解剖图像轴向切片，其位置由蓝线表示，在右侧的矢状切片（如每行所示）。电极位置在矢状视图中以白色示出。行2:T2 *加权的回波平面图像切片显示由于电极和/或电极凝胶而没有信号丢失。在矢状平面上，相应体积的定位显示为覆盖（也可以在每一行中看到）。第3行:从使用tACS设置获取的数据计算出的TSNR图，并打开，但不刺激。第4行:使用tACS设置获取的数据计算出的TSNR图，并以16 Hz刺激。 <a href="http://ecsource.jove.com/files/ftp_upload/55866/55866fig3large.jpg" target="_blank">请点击此处查看此图的较大版本。</a> 图4:由于受污染的电极引起的信号丢失。使用污染电极获取的受试者的fMRI量的切片大致位于运动皮质的手柄上。红色圆圈表示具有信号丢失的电极下面的区域。 <a href="http://ecsource.jove.com/files/ftp_upload/55866/55866fig4large.jpg" target="_blank">请点击此处查看此图的较大版本。</a> <img alt="图5" class="xfigimg" src="/files/ftp_upload/55866/55866fig5.jpg" /> 图5:电流强度对BOLD信号的tACS调制的影响。 （ A ）F分数图显示当前强度对16 Hz tACS影响的主要影响。当前强度在单向rANOVA中的重要主要影响[<html>因子:电流强度（500,750,1,000,1,500μA）]是明显的。图表显示每个当前强度的tACS-on周期的BOLD信号的事件相关平均时间过程。阴影区域表示对象平均值的标准误差。内侧FG =内侧额回，IPS =脑内龈沟，IFG =下额叶回，PrC =中央回，L =左，R =右，*未对多次比较进行校正。 （ B ）T分数图显示每个当前强度的16 Hz tACS期间的BOLD活动变化。 500μAtACS无明显影响。 LH =左半球; RH =右半球这张照片已从Cabral-Calderin 等人修改29 。 <a href="http://ecsource.jove.com/files/ftp_upload/55866/55866fig5large.jpg" target="_blank">请点击此处查看此图的较大版本。</a> img"src ="/ files / ftp_upload / 55866 / 55866fig6.jpg"/&gt; 图6:视觉感知任务中tACS对BOLD信号的影响。 （ A ）实验示意图。视觉刺激和tACS应用于块设计，在120秒的视觉刺激呈现模块中发生30秒的开 - 关tACS块。每个频率都在不同的会话中进行了测试。 SfM =运动结构。 （ B ）TACS条件和频率相互作用效应。 F统计图显示双向rANOVA [内因子:tACS（开，关），频率（10Hz，60Hz，80Hz）]的显着性，以及中后回后两个代表性簇的β估计。连续线和黑色星号标志着10 Hz与60 Hz和10 Hz对80 Hz的tACS开关间相互作用影响的事后比较的显着差异，而红色星号意味着tACS对与事件后检测的显着差异。 PoC =中央回，IPS =脑内龈沟（ C ）60 Hz tACS的T分数图。比较60 Hz tACS对比显着差异。这张照片已经从Cabral-Calderin 等人转载29 。 <a href="http://ecsource.jove.com/files/ftp_upload/55866/55866fig6large.jpg" target="_blank">请点击此处查看此图的较大版本。</a>

Watch this Scientific Journal Video about Simultaneous Transcranial Alternating Current Stimulation and Functional Magnetic Resonance Imaging at JoVE.com

Simultaneous Transcranial Alternating Current Stimulation and Functional Magnetic Resonance Imaging

经颅交感刺激（tACS）是脑振荡无创检测的有前途的工具，尽管其影响尚未完全清楚。本文介绍了一种安全可靠的设置，可与功能磁共振成像同时应用tACS，从而增强理解振荡脑功能和tACS的作用。

同时经颅交替电流刺激和功能磁共振成像

Transcranial alternating current stimulation (tACS) is a promising tool for noninvasive investigation of brain oscillations. TACS employs ...

simultaneous-transcranial-alternating-current-stimulation-functional

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SCIENTISTS IN ACTION

13.9K 次观看.  University Medicine Goettingen. 经颅交感刺激（tACS）是脑振荡无创检测的有前途的工具，尽管其影响尚未完全清楚。本文介绍了一种安全可靠的设置，可与功能磁共振成像同时应用tACS，从而增强理解振荡脑功能和tACS的作用。 

视频: Simultaneous Transcranial Alternating Current Stimulation and Functional Magnetic Resonance Imaging

Best Current Practice for Obtaining High Quality EEG Data During Simultaneous fMRI

Simultaneous EEG-fMRI allows the excellent temporal resolution of EEG to be combined with the high spatial accuracy of fMRI. The data from these two modalities can be combined in a number of ways, but all rely on the acquisition of high quality EEG and fMRI data. EEG data acquired during simultaneous fMRI are affected by several artifacts, including the gradient artefact (due to the changing magnetic field gradients required for fMRI), the pulse artefact (linked to the cardiac cycle) and movement artifacts (resulting from movements in the strong magnetic field of the scanner, and muscle activity). Post-processing methods for successfully correcting the gradient and pulse artifacts require a number of criteria to be satisfied during data acquisition. Minimizing head motion during EEG-fMRI is also imperative for limiting the generation of artifacts.
Interactions between the radio frequency (RF) pulses required for MRI and the EEG hardware may occur and can cause heating. This is only a significant risk if safety guidelines are not satisfied. Hardware design and set-up, as well as careful selection of which MR sequences are run with the EEG hardware present must therefore be considered.
The above issues highlight the importance of the choice of the experimental protocol employed when performing a simultaneous EEG-fMRI experiment. Based on previous research we describe an optimal experimental set-up. This provides high quality EEG data during simultaneous fMRI when using commercial EEG and fMRI systems, with safety risks to the subject minimized. We demonstrate this set-up in an EEG-fMRI experiment using a simple visual stimulus. However, much more complex stimuli can be used. Here we show the EEG-fMRI set-up using a Brain Products GmbH (Gilching, Germany) MRplus, 32 channel EEG system in conjunction with a Philips Achieva (Best, Netherlands) 3T MR scanner, although many of the techniques are transferable to other systems.

Simultaneous electroencephalography (EEG) and functional Magnetic Resonance imaging (fMRI) is a powerful neuroimaging tool. However, the inside of an MRI scanner forms a difficult environment for EEG data recording and safety must be considered whenever operating EEG equipment inside a scanner. Here, we present an optimised EEG-fMRI data acquisition protocol.

获得高质量的脑电数据在同步功能磁共振成像的当前最佳实践

Simultaneous  EEG-fMRI allows the excellent temporal resolution of EEG to be combined with the  high spatial accuracy of fMRI. The data  from these two ...

科研

行为学

Transcranial Direct Current Stimulation and Simultaneous  Functional Magnetic Resonance Imaging

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp to manipulate cortical excitability and, consequently, behavior and brain function. In the last decade, numerous studies have addressed short-term and long-term effects of tDCS on different measures of behavioral performance during motor and cognitive tasks, both in healthy individuals and in a number of different patient populations. So far, however, little is known about the neural underpinnings of tDCS-action in humans with regard to large-scale brain networks. This issue can be addressed by combining tDCS with functional brain imaging techniques like functional magnetic resonance imaging (fMRI) or electroencephalography (EEG).
In particular, fMRI is the most widely used brain imaging technique to investigate the neural mechanisms underlying cognition and motor functions. Application of tDCS during fMRI allows analysis of the neural mechanisms underlying behavioral tDCS effects with high spatial resolution across the entire brain. Recent studies using this technique identified stimulation induced changes in task-related functional brain activity at the stimulation site&#160;and also in more distant brain regions, which were associated with behavioral improvement. In addition, tDCS administered during resting-state fMRI allowed identification of widespread changes in whole brain functional connectivity.
Future studies using this combined protocol should yield new insights into the mechanisms of tDCS action in health and disease and new options for more targeted application of tDCS in research and clinical settings. The present manuscript describes this novel technique in a step-by-step fashion, with a focus on technical aspects of tDCS administered during fMRI.

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique. It has successfully been used in basic research and clinical settings to modulate brain function in humans. This article describes the implementation of tDCS and simultaneous functional magnetic resonance imaging (fMRI), to investigate the neural basis of tDCS effects.

经颅直流电刺激和同步功能磁共振成像

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that uses weak electrical currents administered to the scalp ...

Combining Transcranial Magnetic Stimulation and fMRI to Examine the Default Mode Network

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful rest."1,2,3 It is thought the default mode network corresponds to self-referential or "internal mentation".2,3
It has been hypothesized that, in humans, activity within the default mode network is correlated with certain pathologies (for instance, hyper-activation has been linked to schizophrenia 4,5,6 and autism spectrum disorders 7 whilst hypo-activation of the network has been linked to Alzheimer's and other neurodegenerative diseases 8). As such, noninvasive modulation of this network may represent a potential therapeutic intervention for a number of neurological and psychiatric pathologies linked to abnormal network activation. One possible tool to effect this modulation is Transcranial Magnetic Stimulation: a non-invasive neurostimulatory and neuromodulatory technique that can transiently or lastingly modulate cortical excitability (either increasing or decreasing it) via the application of localized magnetic field pulses.9
In order to explore the default mode network's propensity towards and tolerance of modulation, we will be combining TMS (to the left inferior parietal lobe) with functional magnetic resonance imaging (fMRI). Through this article, we will examine the protocol and considerations necessary to successfully combine these two neuroscientific tools.

In this article, we examine the methodology and considerations relevant to the combination of TMS and fMRI to examine the effects of brain stimulation on the default network.

结合经颅磁刺激和功能磁共振成像检查默认模式网络

The default mode network is a group of brain regions that are active when an individual is not focused on the outside world and the brain is at "wakeful ...

神经科学

Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation (tACS)

Oscillatory brain activities are considered to reflect the basis of rhythmic changes in transmission efficacy across brain networks and are assumed to integrate cognitive neural processes. Transcranial alternating current stimulation (tACS) holds the promise to elucidate the causal link between specific frequencies of oscillatory brain activity and cognitive processes. Simultaneous electroencephalography (EEG) recording during tACS would offer an opportunity to directly explore immediate neurophysiological effects of tACS. However, it is not trivial to measure EEG signals during tACS, as tACS creates a huge artifact in EEG data. Here we explain how to set up concurrent tACS-EEG experiments. Two necessary considerations for successful EEG recording while applying tACS are highlighted. First, bridging of the tACS and EEG electrodes via leaking EEG gel immediately saturates the EEG amplifier. To avoid bridging via gel, the viscosity of the EEG gel is the most important parameter. The EEG gel must be viscous to avoid bridging, but at the same time sufficiently fluid to create contact between the tACS electrode and the scalp. Second, due to the large amplitude of the tACS artifact, it is important to consider using an EEG system with a high resolution analog-to-digital (A/D) converter. In particular, the magnitude of the tACS artifact can exceed 100 mV at the vicinity of a stimulation electrode when 1 mA tACS is applied. The resolution of the A/D converter is of importance to measure good quality EEG data from the vicinity of the stimulation site. By following these guidelines for the procedures and technical considerations, successful concurrent EEG recording during tACS will be realized.

Concurrent Electroencephalography Recording During Transcranial Alternating Current Stimulation tACS

In this article we explain how to set up a concurrent transcranial alternating current stimulation and EEG experiment.

并行脑电图记录在经颅交流电刺激（TACS）

Oscillatory brain activities are considered to reflect the basis of rhythmic changes in transmission efficacy across brain networks and are assumed to ...

Extracting Visual Evoked Potentials from EEG Data Recorded During fMRI-guided Transcranial Magnetic Stimulation

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological effects. Specifically, by creating a transient interference with the normal activity of a target region and measuring changes in an electrophysiological signal, we can establish a causal link between the stimulated brain area or network and the electrophysiological signal that we record. If target brain areas are functionally defined with prior fMRI scan, TMS could be used to link the fMRI activations with evoked potentials recorded. However, conducting such experiments presents significant technical challenges given the high amplitude artifacts introduced into the EEG signal by the magnetic pulse, and the difficulty to successfully target areas that were functionally defined by fMRI. Here we describe a methodology for combining these three common tools: TMS, EEG, and fMRI. We explain how to guide the stimulator&#39;s coil to the desired target area using anatomical or functional MRI data, how to record EEG during concurrent TMS, how to design an ERP study suitable for EEG-TMS combination and how to extract reliable ERP from the recorded data. We will provide representative results from a previously published study, in which fMRI-guided TMS was used concurrently with EEG to show that the face-selective N1 and the body-selective N1 component of the ERP are associated with distinct neural networks in extrastriate cortex. This method allows us to combine the high spatial resolution of fMRI with the high temporal resolution of TMS and EEG and therefore obtain a comprehensive understanding of the neural basis of various cognitive processes.

This paper describes a method for collecting and analyzing electroencephalography (EEG) data during concurrent transcranial magnetic stimulation (TMS) guided by activations revealed with functional magnetic resonance imaging (fMRI). A method for TMS artifact removal and extraction of event related potentials is described as well as considerations in paradigm design and experimental setup.

提取脑电数据视觉诱发电位记录在功能磁共振成像引导下经颅磁刺激

Transcranial Magnetic Stimulation (TMS) is an effective method for establishing a causal link between a cortical area and cognitive/neurophysiological ...

Effects of Transcranial Alternating Current Stimulation on the Primary Motor Cortex by Online Combined Approach with Transcranial Magnetic Stimulation

Transcranial Alternating Current Stimulation (tACS) is a neuromodulatory technique able to act through sinusoidal electrical waveforms in a specific frequency and in turn modulate ongoing cortical oscillatory activity. This neurotool allows the establishment of a causal link between endogenous oscillatory activity and behavior. Most of the tACS studies have shown online effects of tACS. However, little is known about the underlying action mechanisms of this technique because of the AC-induced artifacts on Electroencephalography (EEG) signals. Here we show a unique approach to investigate online physiological frequency-specific effects of tACS of the primary motor cortex (M1) by using single pulse Transcranial Magnetic Stimulation (TMS) to probe cortical excitability changes. In our setup, the TMS coil is placed over the tACS electrode while Motor Evoked Potentials (MEPs) are collected to test the effects of the ongoing M1-tACS. So far, this approach has mainly been used to study the visual and motor systems. However, the current tACS-TMS setup can pave the way for future investigations of cognitive functions. Therefore, we provide a step-by-step manual and video guidelines for the procedure.

Transcranial Alternating Current Stimulation (tACS) allows the modulation of cortical excitability in a frequency-specific fashion. Here we show a unique approach which combines online tACS with single pulse Transcranial Magnetic Stimulation (TMS) in order to "probe" cortical excitability by means of Motor Evoked Potentials.

经颅磁刺激在线联合方法对经颅交流电刺激对原发性运动皮层的影响

Transcranial Alternating Current Stimulation (tACS) is a neuromodulatory technique able to act through sinusoidal electrical waveforms in a specific ...

Mapping the After-effects of Theta Burst Stimulation on the Human Auditory Cortex with Functional Imaging

Auditory cortex pertains to the processing of sound, which is at the basis of speech or music-related processing1. However, despite considerable recent progress, the functional properties and lateralization of the human auditory cortex are far from being fully understood. Transcranial Magnetic Stimulation (TMS) is a non-invasive technique that can transiently or lastingly modulate cortical excitability via the application of localized magnetic field pulses, and represents a unique method of exploring plasticity and connectivity. It has only recently begun to be applied to understand auditory cortical function 2. 
An important issue in using TMS is that the physiological consequences of the stimulation are difficult to establish. Although many TMS studies make the implicit assumption that the area targeted by the coil is the area affected, this need not be the case, particularly for complex cognitive functions which depend on interactions across many brain regions 3. One solution to this problem is to combine TMS with functional Magnetic resonance imaging (fMRI). The idea here is that fMRI will provide an index of changes in brain activity associated with TMS. Thus, fMRI would give an independent means of assessing which areas are affected by TMS and how they are modulated 4. In addition, fMRI allows the assessment of functional connectivity, which represents a measure of the temporal coupling between distant regions. It can thus be useful not only to measure the net activity modulation induced by TMS in given locations, but also the degree to which the network properties are affected by TMS, via any observed changes in functional connectivity.
Different approaches exist to combine TMS and functional imaging according to the temporal order of the methods. Functional MRI can be applied before, during, after, or both before and after TMS. Recently, some studies interleaved TMS and fMRI in order to provide online mapping of the functional changes induced by TMS 5-7. However, this online combination has many technical problems, including the static artifacts resulting from the presence of the TMS coil in the scanner room, or the effects of TMS pulses on the process of MR image formation. But more importantly, the loud acoustic noise induced by TMS (increased compared with standard use because of the resonance of the scanner bore) and the increased TMS coil vibrations (caused by the strong mechanical forces due to the static magnetic field of the MR scanner) constitute a crucial problem when studying auditory processing. 
This is one reason why fMRI was carried out before and after TMS in the present study. Similar approaches have been used to target the motor cortex 8,9, premotor cortex 10, primary somatosensory cortex 11,12 and language-related areas 13, but so far no combined TMS-fMRI study has investigated the auditory cortex. The purpose of this article is to provide details concerning the protocol and considerations necessary to successfully combine these two neuroscientific tools to investigate auditory processing. 
Previously we showed that repetitive TMS (rTMS) at high and low frequencies (resp. 10 Hz and 1 Hz) applied over the auditory cortex modulated response time (RT) in a melody discrimination task 2. We also showed that RT modulation was correlated with functional connectivity in the auditory network assessed using fMRI: the higher the functional connectivity between left and right auditory cortices during task performance, the higher the facilitatory effect (i.e. decreased RT) observed with rTMS. However those findings were mainly correlational, as fMRI was performed before rTMS. Here, fMRI was carried out before and immediately after TMS to provide direct measures of the functional organization of the auditory cortex, and more specifically of the plastic reorganization of the auditory neural network occurring after the neural intervention provided by TMS. 
Combined fMRI and TMS applied over the auditory cortex should enable a better understanding of brain mechanisms of auditory processing, providing physiological information about functional effects of TMS. This knowledge could be useful for many cognitive neuroscience applications, as well as for optimizing therapeutic applications of TMS, particularly in auditory-related disorders.

Auditory processing is the basis of speech and music-related processing. Transcranial Magnetic Stimulation (TMS) has been used successfully to study cognitive, sensory and motor systems but has rarely been applied to audition. Here we investigated TMS combined with functional Magnetic Resonance Imaging to understand the functional organization of auditory cortex.

映射后的Theta突发刺激对人类听觉皮层功能成像

Auditory cortex pertains to the processing of sound, which is at the basis of speech or music-related processing1. However, despite considerable recent ...

生物学

Combined Transcranial Magnetic Stimulation and Electroencephalography of the Dorsolateral Prefrontal Cortex

Transcranial magnetic stimulation (TMS) is a non-invasive method that produces neural excitation in the cortex by means of brief, time-varying magnetic field pulses. The initiation of cortical activation or its modulation depends on the background activation of the neurons of the cortical region activated, the characteristics of the coil, its position and its orientation with respect to the head. TMS combined with simultaneous electrocephalography (EEG) and neuronavigation (nTMS-EEG) allows for the assessment of cortico-cortical excitability and connectivity in almost all cortical areas in a reproducible manner. This advance makes nTMS-EEG a powerful tool that can accurately assess brain dynamics and neurophysiology in test-retest paradigms that are required for clinical trials. Limitations of this method include artifacts that cover the initial brain reactivity to stimulation. Thus, the process of removing artifacts may also extract valuable information. Moreover, the optimal parameters for dorsolateral prefrontal (DLPFC) stimulation are not fully known and current protocols utilize variations from the motor cortex (M1) stimulation paradigms. However, evolving nTMS-EEG designs hope to address these issues. The protocol presented here introduces some standard practices for assessing neurophysiological functioning from stimulation to the DLPFC that can be applied in patients with treatment resistant psychiatric disorders that receive treatment such as transcranial direct current stimulation (tDCS), repetitive transcranial magnetic stimulation (rTMS), magnetic seizure therapy (MST) or electroconvulsive therapy (ECT).

The protocol presented here is for TMS-EEG studies utilizing intracortical excitability test-retest design paradigms. The intent of the protocol is to produce reliable and reproducible cortical excitability measures for assessing neurophysiological functioning related to therapeutic interventions in the treatment of neuropsychiatric diseases such as major depression.

侧前额叶皮质联合经颅磁刺激与脑电图的研究

Transcranial magnetic stimulation (TMS) is a non-invasive method that produces neural excitation in the cortex by means of brief, time-varying magnetic ...

Concurrent EEG and Functional MRI Recording and Integration Analysis for Dynamic Cortical Activity Imaging

Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) are two of the fundamental noninvasive methods for identifying brain activity. Multimodal methods have sought to combine the high temporal resolution of EEG with the spatial precision of fMRI, but the complexity of this approach is currently in need of improvement. The protocol presented here describes the recently developed spatiotemporal fMRI-constrained EEG source imaging method, which seeks to rectify source biases and improve EEG-fMRI source localization through the dynamic recruitment of fMRI sub-regions. The process begins with the collection of multimodal data from concurrent EEG and fMRI scans, the generation of 3D cortical models, and independent EEG and fMRI processing. The processed fMRI activation maps are then split into multiple priors, according to their location and surrounding area. These are taken as priors in a two-level hierarchical Bayesian algorithm for EEG source localization. For each window of interest (defined by the operator), specific segments of the fMRI activation map will be identified as active to optimize a parameter known as model evidence. These will be used as soft constraints on the identified cortical activity, increasing the specificity of the multimodal imaging method by reducing cross-talk and avoiding erroneous activity in other conditionally active fMRI regions. The method generates cortical maps of activity and time-courses, which may be taken as final results, or used as a basis for further analyses (analyses of correlation, causation, etc.) While the method is somewhat limited by its modalities (it will not find EEG-invisible sources), it is broadly compatible with most major processing software, and is suitable for most neuroimaging studies.

An EEG-fMRI multimodal imaging method, known as the spatiotemporal fMRI-constrained EEG source imaging method, is described here. The presented method employs conditionally-active fMRI sub-maps, or priors, to guide EEG source localization in a manner that improves spatial specificity and limits erroneous results.

动态皮层活动影像的并发脑电图与功能 MRI 记录及积分分析

Electroencephalography (EEG) and functional magnetic resonance imaging (fMRI) are two of the fundamental noninvasive methods for identifying brain ...

<meta charset="utf8"></head><body>神经导航 tDCS 提高 fMRI 研究中电极放置的准确性

Neuronavigated Focalized Transcranial Direct Current Stimulation Administered During Functional Magnetic Resonance Imaging

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that allows the modulation of the excitability and plasticity of the human brain. Focalized tDCS setups use specific electrode arrangements to constrain the current flow to circumscribed brain regions. However, the effectiveness of focalized tDCS can be compromised by electrode positioning errors on the scalp, resulting in significant reductions of the current dose reaching the target brain regions for tDCS. Electrode placement guided by neuronavigation based on the individual&#39;s head and brain anatomy derived from structural magnetic resonance imaging (MRI) data may be suited to improve positioning accuracy.
This protocol describes the method of neuronavigated electrode placement for a focalized tDCS setup, which is suitable for concurrent administration during functional MRI (fMRI). We also quantify the accuracy of electrode placement and investigate electrode drift in a concurrent tDCS-fMRI experiment. Critical steps involve the optimization of electrode positions based on current modeling that considers the individual&#39;s head and brain anatomy, the implementation of neuronavigated electrode placement on the scalp, and the administration of optimized and focal tDCS during fMRI.
The regional precision of electrode placement is quantified using the Euclidean norm (L2&#160;Norm) to determine deviations of the actual from the intended electrode positions during a concurrent tDCS-fMRI study. Any potential displacement of electrodes (drift) during the experiment is investigated by comparing actual electrode positions before and after the fMRI acquisition. In addition, we directly compare the placement accuracy of neuronavigated tDCS to that achieved by a scalp-based targeting approach (a 10-20 Electroencephalography (EEG) system). These analyses demonstrate superior placement accuracy for neuronavigation compared to scalp-based electrode placement and negligible electrode drift across a 20 min scanning period.

<meta charset="utf8"></head><body>在功能磁共振成像期间进行神经导航聚焦经颅直流电刺激

This protocol describes the method of neuronavigated electrode placement for focal, transcranial direct current stimulation (tDCS) administered during functional magnetic resonance imaging (fMRI).

在功能磁共振成像期间进行神经导航聚焦经颅直流电刺激

Transcranial direct current stimulation (tDCS) is a noninvasive brain stimulation technique that allows the modulation of the excitability and plasticity ...