Ukharova Elena, Sathyan Sabin, Granö Ida, O'Meeghan Isabella, Ahola Oskari, Kainulainen Noora, Laurinoja Joonas, Partanen Paula, Aydogan Dogu Baran, Ilmoniemi Risto J, Roine Timo, Lioumis Pantelis
Department of Neuroscience and Biomedical Engineering, Aalto University School of Science;
Department of Neuroscience and Biomedical Engineering, Aalto University School of Science.
J Vis Exp. 2025 Jun 13(220). doi: 10.3791/67339.
The cerebral cortex is organized into structurally and functionally segregated networks, enabling the human brain to process information highly efficiently. Transcranial magnetic stimulation (TMS), in combination with electroencephalography (EEG), offers a non-invasive approach to probing brain networks, revealing cortical excitability and causal connectivity. However, this method faces two significant challenges: (a) ensuring the quality of TMS-evoked potentials (TEPs) to maximize information gain, often requiring comprehensive cortical mapping, and (b) eliciting the response from the network of interest and not from adjacent cortical sites. Existing TMS targeting approaches frequently fail to precisely stimulate functionally relevant cortical areas, hindering treatment efficacy and the identification of biomarkers. The presented protocol integrates precise cortical mapping to acquire artifact-free TEPs, enabling reliable and reproducible measurements of early TEP components. This precision improves sensitivity to subtle neurophysiological variations and strengthens correlations with clinical phenotypes, supporting biomarker discovery in neuropsychiatric disorders. The proposed protocol utilizes structural, functional, and diffusion magnetic resonance imaging (MRI) to identify cortical patches belonging to the network of interest. Anatomical parcellation, functional connectivity, and real-time tractography are applied to locate areas with strong connectivity to other brain regions associated with the target network. The resulting personalized cortical clusters define the initial stimulation targets. TMS-EEG mapping is then employed to optimize TMS parameters by localizing cortical areas with high excitability, enhancing neuronal response magnitude while reducing non-neuronal noise, including muscle artifacts, decay, and other confounding factors affecting early TMS-EEG responses. A systematic exploration of the cortical mantle is conducted, adjusting stimulation location, orientation, and intensity, with continuous data quality monitoring through real-time visualization of averaged TEPs. TMS parameters producing artifact-free responses with clearly discernible early TEP components are selected for data collection. This article introduces the neuroimaging-guided TMS-EEG mapping technique and highlights the methodological advancements and benefits achievable through its application.
大脑皮层被组织成结构和功能上分离的网络，使人类大脑能够高效地处理信息。经颅磁刺激（TMS）与脑电图（EEG）相结合，提供了一种非侵入性的方法来探测脑网络，揭示皮层兴奋性和因果连接性。然而，这种方法面临两个重大挑战：（a）确保TMS诱发电位（TEP）的质量以最大化信息增益，这通常需要全面的皮层映射；（b）从感兴趣的网络而非相邻皮层部位引出反应。现有的TMS靶向方法常常无法精确刺激功能相关的皮层区域，从而阻碍了治疗效果和生物标志物的识别。本文提出的方案整合了精确的皮层映射以获取无伪迹的TEP，从而能够对早期TEP成分进行可靠且可重复的测量。这种精确性提高了对细微神经生理变化的敏感性，并加强了与临床表型的相关性，有助于神经精神疾病中生物标志物的发现。所提出的方案利用结构、功能和扩散磁共振成像（MRI）来识别属于感兴趣网络的皮层区域。应用解剖学分割、功能连接和实时纤维束成像来定位与目标网络相关的其他脑区具有强连接的区域。由此产生的个性化皮层簇定义了初始刺激靶点。然后采用TMS-EEG映射通过定位高兴奋性的皮层区域来优化TMS参数，增强神经元反应幅度，同时减少非神经元噪声，包括肌肉伪迹、衰减以及其他影响早期TMS-EEG反应的混杂因素。对皮层进行系统探索，调整刺激位置、方向和强度，并通过对平均TEP的实时可视化持续监测数据质量。选择产生无伪迹反应且早期TEP成分清晰可辨的TMS参数进行数据收集。本文介绍了神经影像引导的TMS-EEG映射技术，并强调了通过其应用可实现的方法学进展和益处。
