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

Abstract

ABSTRACTElectroencephalography (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.