Combining functional near-infrared spectroscopy and magnetoencephalography based on optically pumped magnetometers for advanced mapping of neurovascular coupling

• Applicant: Dr. Tilmann Sander-Thömmes
• Subject Area: Biomedical Systems Technology ; Medical Physics, Biomedical Technology
• Term: since 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 505063244

Neurovascular coupling (NVC) is the basic mechanism of providing energy to active brain areas. To study the NVC one requires simultaneously acquired data from two brain imaging modalities. In our project, we will develop a methodology based on two non-invasive brain imaging modalities: functional near-infrared spectroscopy (fNIRS) and magnetoencephalography (MEG). fNIRS estimates cortical hemodynamic activity by measuring changes both in oxy- and deoxyhemoglobin concentration. MEG determines activity within the cortex based on the measurement of magnetic fields near the head. Standard MEG systems use costly liquid helium for cooling the superconducting SQUID sensors, but in this project, we will use the novel optically pumped magnetometers (OPM). MEG based on OPMs (oMEG) does not need cooling with cryogenics, therefore these sensors can be applied freely for measurements, like fNIRS optodes. This opens a plethora of new applications to study NVC under conditions, where a subject is performing natural tasks including movements. Until recently, the only combination of modalities that allowed movement was electroencephalography (EEG) and fNIRS. MEG has a major advantage over EEG, it has higher spatial resolution since its inverse solution is more accurate. fNIRS optodes attached to the head do not require any electronics and its housing can be paramagnetic. Therefore, they do not interfere with the MEG sensor's operation as it was shown in one preliminary study of us.The combined oMEG-fNIRS system will consist of three crucial parts: fNIRS optodes, OPMs and a sensor holder, which will have slots for both type of sensors. With this holder the sensors will be placed directly onto the subject's scalp. The sensor holder will be 3D printed for each subject separately; the model will be built by extracting the surface points of the subject's head from magnetic resonance images. The goal of this study to demonstrate an advanced methodology for assessing the NVC, therefore we will use combined oMEG-fNIRS to measure a group of subjects performing several tasks. Paradigms will include single sensory tasks like listening to a tone, a resting-state condition, and complex tasks involving motor responses triggered by a cognitive exercise. These complex tasks induce network activity between, e.g., visual and motor areas of the cortex. To parametrize the extracted NVC patterns, we will compare and combine the measurements made with both modalities using various computational methods: cross-correlation and spectral analysis; calculating the source reconstruction; calculating the functional connectivity.

• DFG Programme: Research Grants
• International Connection: Poland, Slovenia
• Partner Organisation: Slovenian Research Agency (ARRS)
• Cooperation Partners: Professor Dr. Zvonko Jaglicic; Professor Adam Stefan Liebert, Ph.D.