Inferring laminar origins of MEG signals with optically pumped magnetometers (OPMs)

COEX 

Magnetoencephalography (MEG) is a non-invasive technique that measures the tiny magnetic fields generated by neural currents in the brain. Conventional MEG operates with superconducting SQUID magnetometers that must be immersed in liquid helium for cooling, which introduces a substantial gap between the sensors and the scalp. Optically-pumped magnetometers (OPMs) are new, highly sensitive magnetometers that operate without the need for cryogenic cooling and can be placed close to the scalp, substantially improving sensitivity to cortical sources (Boto et al., 2016, Iivanainen et al., 2017). The typical spatial resolution achieved by conventional MEG is not sufficient for laminar inference. One strategy to distinguish between deep and superficial sources is to use high-precision forward models that exploit the small variations in the so-called lead fields between deep and superficial sources (Bonaiuto et al., 2018a and 2018b). On-scalp OPM-MEG has been suggested to further improve the discriminability of laminar sources. To investigate this, we simulate cortical sources at deep and superficial layers and infer their laminar origin using OPM sensor arrays with varying numbers of sensors and measurement axes.