Measurement of Frontal Midline Theta Oscillations using OPM-MEG
Natalie Rhodes,
Molly Rea,
Elena Boto,
Lukas Rier,
Vishal Shah,
Ryan M. Hill,
James Osborne,
Cody Doyle,
Niall Holmes,
Sebastian C. Coleman,
Karen Mullinger,
Richard Bowtell,
Matthew J. Brookes
Affiliations
Natalie Rhodes
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
Molly Rea
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
Elena Boto
Cerca Magnetics Ltd. 2, Castlebridge Office Village, Kirtley Dr, Nottingham NG7 1LD; Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
Lukas Rier
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
Vishal Shah
QuSpin Inc. 331 South 104th Street, Suite 130, Louisville, Colorado, 80027, USA
Ryan M. Hill
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK; Cerca Magnetics Ltd. 2, Castlebridge Office Village, Kirtley Dr, Nottingham NG7 1LD
James Osborne
QuSpin Inc. 331 South 104th Street, Suite 130, Louisville, Colorado, 80027, USA
Cody Doyle
QuSpin Inc. 331 South 104th Street, Suite 130, Louisville, Colorado, 80027, USA
Niall Holmes
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK; Cerca Magnetics Ltd. 2, Castlebridge Office Village, Kirtley Dr, Nottingham NG7 1LD
Sebastian C. Coleman
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
Karen Mullinger
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK; Centre for Human Brain Health, School of Psychology, University of Birmingham, Birmingham, B15 2TT, UK
Richard Bowtell
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK
Matthew J. Brookes
Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham, NG7 2RD, UK; Cerca Magnetics Ltd. 2, Castlebridge Office Village, Kirtley Dr, Nottingham NG7 1LD; Corresponding author at: Sir Peter Mansfield Imaging Centre, School of Physics and Astronomy, University of Nottingham, University Park, Nottingham NG7 2RD, United Kingdom.
Optically pumped magnetometers (OPMs) are an emerging lightweight and compact sensor that can measure magnetic fields generated by the human brain. OPMs enable construction of wearable magnetoencephalography (MEG) systems, which offer advantages over conventional instrumentation. However, when trying to measure signals at low frequency, higher levels of inherent sensor noise, magnetic interference and movement artefact introduce a significant challenge. Accurate characterisation of low frequency brain signals is important for neuroscientific, clinical, and paediatric MEG applications and consequently, demonstrating the viability of OPMs in this area is critical. Here, we undertake measurement of theta band (4–8 Hz) neural oscillations and contrast a newly developed 174 channel triaxial wearable OPM-MEG system with conventional (cryogenic-MEG) instrumentation. Our results show that visual steady state responses at 4 Hz, 6 Hz and 8 Hz can be recorded using OPM-MEG with a signal-to-noise ratio (SNR) that is not significantly different to conventional MEG. Moreover, we measure frontal midline theta oscillations during a 2-back working memory task, again demonstrating comparable SNR for both systems. We show that individual differences in both the amplitude and spatial signature of induced frontal-midline theta responses are maintained across systems. Finally, we show that our OPM-MEG results could not have been achieved without a triaxial sensor array, or the use of postprocessing techniques. Our results demonstrate the viability of OPMs for characterising theta oscillations and add weight to the argument that OPMs can replace cryogenic sensors as the fundamental building block of MEG systems.