Hybridised Quantum Optical Sensors for enhanced magnetoencephalography

The human brain is the most complex organ and the most complex computational system that we know of. When something goes wrong in the brain because of an injury or disorder, we want to quickly and accurately deal with those problems. But because of the inherent complexity of the brain, achieving the level of precision of imaging and stimulation needed to diagnose and treat these disorders is challenging. Sensing and stimulating neurons at a high resolution is hard enough even when electrodes are implanted in the brain, but another layer of extreme complexity is added if you want to achieve this noninvasively, through the skull. In this project I will achieve a significant step-change and technological development required in the accessibility, acquisition, viewing and diagnostic usage of brain signals for neuroimaging by combining functional Near Infrared Spectroscopy (fNIRS) with magnetoencephalography (MEG) based on Optically Pumped Magnetometers (OPM) which I will interfere with Transcranial Magnetic Stimulation (TMS).

MEG is a non-invasive technique for imaging electrophysiological brain activity. Dendritic current flow generates small changes in the magnetic field outside the head. An array of highly sensitive magnetometers detects these changes and 3-dimensional images depicting moment-to-moment changes in brain activity are reconstructed. OPMs are a novel type of quantum sensors for MEG as they allow measuring small magnetic fields such as neuronal currents in the brain. fNIRS devices transmit harmless light into tissue and measure the reflected light, which contains information about the dynamics of blood flow in underlying tissue. As fNIRS can measure the vascular signal, it is shown to quantify functional connectivity within the intrinsic neuronal networks, comparable to fMRI. Furthermore, fNIRS can also provide an equivalent measure of the PET metabolism biomarker (blood activity) for brain health diagnosis, without the need to expose the patient to radiation. Finally, fNIRS recordings do not interfere with OPM-MEG recordings (or vice versa) and can not only be acquired simultaneously but within the same sensor. Consequently, a simultaneous fNIRS-OPM recording of brain function will provide, for the first time, a measure of all three primary biomarkers of brain health in a subject's natural environment. Specifically, cerebral metabolism, intrinsic network connectivity, and neural oscillations will be measured.

In this project I will develop Hybridised Quantum Optical Sensors (HyQuOS) that will be the first to use the same technology for all measurements without the need for bulky equipment and will provide two contrast-rich signals: those of neural and vascular response, simultaneously, creating a sensor that will be richer than either alone. Finally, my sensor can be built to be resistant to the high magnetic field pulses of TMS. By combining HyQuOS with TMS, it will be possible to focally excite one part of the brain and measure the response in another part with great precision. This will allow us for the first time to directly assess connectivity in the brain in a causal manner, to measure how this connectivity changes when different brain networks are engaged in different tasks.
Along with clinically derived outcome and neuro-psychometric data, I will demonstrate the potential of HyQuOS for the detection and monitoring of brain signals for cognitive and neuro-connectivity impairment such as mild Traumatic Brain Injury. The long-term goal is to develop a whole-head system with multiple HyQuOS sensors that can be used with multiple TMS coils. Besides greatly enlarging our understanding of brain connectivity, an integrated stimulus-measurement system will bring outstanding new possibilities in the development of drug-free treatment by brain stimulation taking into account the current state of the brain.