Wearable magnetoencephalography

Functional neuroimaging offers a means to understand brain function and dysfunction. Over decades, different technologies have been developed to provide a non-invasive measure of brain activity that could help us to better understand the mechanisms underlying human cognition. Magnetoencephalography (MEG) is one of these techniques which, over the past 30 years, has been increasingly contributing to neuroscientific studies giving insights into human brain electrophysiology, with excellent temporal resolution and surprisingly high spatial resolution. However, MEG hardware has limitations and it has only been in the past few years that alternative technologies have seen a rapid progress with an intent to overcome the drawbacks of conventional MEG devices. The main limitation of MEG systems is that they rely on superconducting quantum interference devices (SQUIDs) to measure magnetic fields outside the head. This means that they require cryogenic cooling and as a consequence, sensors are fixed in position in a one-size-fits-all helmet. A vacuum is maintained between the subject’s head and the detectors which limits the sensitivity of the measurement, and subjects must remain still in large cumbersome scanners. Advances in the field of quantum technologies mean that magnetic field sensors, such as optically-pumped magnetometers (OPMs), operating at room temperature, are now able to achieve sensitivities similar to that of SQUIDs. This means that room temperature magnetoencephalography (MEG), with a greatly increased flexibility of sensor placement, can now be considered. Furthermore, these new sensors can be placed directly on the scalp surface giving, theoretically, a large increase in the magnitude of the measured signal. In this thesis, we explore the advantages of multi-channel OPM systems using both simulations, and experimental measurements made using commercially available OPMs in combination with a 3D-printed helmet. With the incorporation of field-nulling technologies, we demonstrate a non-restrictive MEG system that could benefit many different participant cohorts, for example children. The results presented highlight the opportunity afforded by OPMs to generate uncooled, potentially low-cost, high sensitivity MEG systems which offer a step change compared to the current generation of cryogenic instrumentation