Abstract
Studies with magnetoencephalography (MEG) are still quite rarely combined simultaneously with methods that can provide a metabolic dimension to MEG investigations. In addition, continuous blood pressure measurements which comply with MEG compatibility requirements are lacking. For instance, by combining methods reflecting neurovascular status one could obtain more information on low frequency fluctuations that have recently gained increasing interest as a mediator of functional connectivity within brain networks. This paper presents a multimodal brain imaging setup, capable to non-invasively and continuously measure cerebral hemodynamic, cardiorespiratory and blood pressure oscillations simultaneously with MEG. In the setup, all methods apart from MEG rely on the use of fibre optics. In particular, we present a method for measuring of blood pressure and cardiorespiratory oscillations continuously with MEG. The potential of this type of multimodal setup for brain research is demonstrated by our preliminary studies on human, showing effects of mild hypercapnia, gathered simultaneously with the presented modalities.
Highlights
Combining different brain imaging techniques enables us to study the causality between complex neurological mechanisms and variables
The very low frequency (VLF) waves are being reflected in combined direct current (DC)-EEG - near-infrared spectroscopy (NIRS) measurements which reflect the stability of the neurovascular unit[8, 9]
We have previously developed an MRI compatible continuous non-invasive blood pressure (BP) measurement method[11] which was utilised for the first time in MEG environment
Summary
Combining different brain imaging techniques enables us to study the causality between complex neurological mechanisms and variables. An increase in neuronal activity causes a metabolic demand for glucose and oxygen, which increases cerebral blood flow to the active brain region This kind of process is impossible to study accurately by any single imaging modality, but requires simultaneous use of hemodynamic and electromagnetic based imaging techniques. Multimodal imaging, such as electroencephalogram (EEG) with magnetoencephalography (MEG) or functional magnetic resonance imaging (fMRI) is a common practice in modern day neuroimaging Such imaging techniques would draw an advantage if cardiovascular and cerebral hemodynamic related signals are recorded comprehensive and in synchrony. In multimodal brain studies it is desirable that at least one modality provides adequate spatial information To realize this issue, MEG can incorporate EEG measures but relies on optical BOLD assessments. While fNIRS and BP provide important information for hemodynamic forward models, their applications in MEG measurements are desirable
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