Simultaneous whole-head electrophysiological recordings using EEG and OPM-MEG

Abstract

Electroencephalography (EEG) and magnetoencephalography (MEG) non-invasively measure human brain electrophysiology. They differ in nature; MEG offers better performance (higher spatial precision) whilst EEG (a wearable platform) is more practical. They are also complementary, with studies showing that concurrent MEG/EEG provides advantages over either modality alone, and consequently clinical guidelines for MEG in epilepsy recommend simultaneous acquisition of EEG. In recent years, new instrumentation, optically pumped magnetometers (OPMs), has had a significant impact on MEG, offering improved performance, lifespan compliance, and wearable sensors. Nevertheless, the ability to carry out simultaneous EEG/OPM-MEG remains critical. Here, we investigated whether simultaneous, wearable, whole-head EEG and OPM-MEG measurably degrades signal quality in either modality. We employed two tasks: a motor task known to modulate beta oscillations, and an eyes-open/eyes-closed task known to modulate alpha oscillations. In both, we characterised the performance of EEG alone, MEG alone, and concurrent EEG/OPM-MEG. Our results show that the SNR of the beta response was very similar, regardless of whether modalities were used individually or concurrently. Likewise, our alpha band recordings demonstrated that signal contrast was stable, regardless of the concurrent recording. These results combined suggest that there are no fundamental barriers to simultaneous wearable EEG/OPM-MEG, and consequently this technique is ripe for neuroscientific and clinical adoption. This will be particularly important in the clinical sphere where a direct comparison between simultaneous EEG and OPM-MEG recordings will facilitate interpretation of OPM-MEG data in patients.

A Novel, Robust, and Portable Platform for Magnetoencephalography using Optically Pumped Magnetometers

“…Figure 6 shows that our IM system can be used simultaneously with EEG to gather multi-modal electrophysiological data. This is not the first time OPM-MEG/EEG has been carried out (e.g., (Boto et al, 2019;Seedat et al, 2023)), but it is noteworthy that it is the first simultaneous OPM-MEG/EEG recording with closed-loop operation and this mode (which requires continual operation of on-board-sensor electromagnetic coils) does not appear to impact significantly the quality of the EEG data. Our aim in this study was simply to demonstrate that concurrent recordings are possible.…”