Detection of human auditory evoked brain signals with a resilient nonlinear optically pumped magnetometer

Kowalczyk, Anna; Bezsudnova, Yulia; Jensen, Ole; Barontini, Giovanni

doi:10.1016/j.neuroimage.2020.117497

Cited by 24 publications

(18 citation statements)

References 24 publications

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“…Considering next the auditory system, our results show that OP-MEG can be used to measure AEFs using 70 ms-long tones, replicating several previous stationary, seated OP-MEG studies ( Borna et al., 2017 ; 2020 ; Kowalczyk et al., 2021 ). Given their reliability ( Hari, 1990 ), AEFs will continue to be a crucial benchmarking tool for OP-MEG development.…”

Section: Discussionsupporting

confidence: 85%

Using OPMs to measure neural activity in standing, mobile participants

et al. 2021

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Optically pumped magnetometer-based magnetoencephalography (OP-MEG) can be used to measure neuromagnetic fields while participants move in a magnetically shielded room. Head movements in previous OP-MEG studies have been up to 20 cm translation and ∼30° rotation in a sitting position. While this represents a step-change over stationary MEG systems, naturalistic head movement is likely to exceed these limits, particularly when participants are standing up. In this proof-of-concept study, we sought to push the movement limits of OP-MEG even further. Using a 90 channel (45-sensor) whole-head OP-MEG system and concurrent motion capture, we recorded auditory evoked fields while participants were: (i) sitting still, (ii) standing up and still, and (iii) standing up and making large natural head movements continuously throughout the recording – maximum translation 120 cm, maximum rotation 198°. Following pre-processing, movement artefacts were substantially reduced but not eliminated. However, upon utilisation of a beamformer, the M100 event-related field localised to primary auditory regions. Furthermore, the event-related fields from auditory cortex were remarkably consistent across the three conditions. These results suggest that a wide range of movement is possible with current OP-MEG systems. This in turn underscores the exciting potential of OP-MEG for recording neural activity during naturalistic paradigms that involve movement (e.g. navigation), and for scanning populations who are difficult to study with stationary MEG (e.g. young children).

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Section: Discussionsupporting

confidence: 85%

Using OPMs to measure neural activity in standing, mobile participants

et al. 2021

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“…In this study, we measured the AEFs using OPM sensors and confirmed that our results replicate the findings of previous OPM studies (Borna et al, 2020;Borna et al, 2017;Kim et al, 2014;Kowalczyk et al, 2021). We found clear M50 and M100 components of AEFs and obtained the topological map pattern.…”

Section: Discussionsupporting

confidence: 90%

“…OPM sensors have been applied to detect neuromagnetic signals with such advantages. Previous OPM-based MEG studies have measured various brain activities relating to auditory evoked fields (AEFs) (Borna et al, 2020;Borna et al, 2017;Kim et al, 2014;Kowalczyk et al, 2021), visual processing (Iivanainen et al, 2020), somatosensory processing (Boto et al, 2017), motor processing (Boto et al, 2018), and language function (de Lange et al, 2021;Tierney et al, 2018).…”

Section: Introductionmentioning

confidence: 99%

Detection of the 40-Hz Auditory Steady-state Response with Optically Pumped Magnetometers

Shim

Kwon

et al. 2021

Preprint

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Magnetoencephalography (MEG) is a functional neuroimaging technique that noninvasively detects the brain magnetic field from neuronal activations. Conventional MEG measures brain signals using superconducting quantum interference devices (SQUIDs). SQUID based MEG requires a cryogenic environment involving a bulky non-magnetic dewar and the consumption of liquid helium, which restricts the variability of the sensor array and the gap between the cortical sources and sensors. Recently, miniature optically pumped magnetometers (OPMs) have been developed and commercialized. OPMs do not require cryogenic cooling and can be placed within millimeters from the scalp. In the present study, we arranged six OPM sensors on the temporal area to detect auditory related brain responses in a two layer magnetically shielded room. We presented the auditory stimuli of 1 kHz pure tone bursts with 200 ms duration and obtained the M50 and M100 components of auditory evoked fields. We delivered the periodic stimuli with a 40 Hz repetition rate and observed the gamma band power changes and inter trial phase coherence of auditory steady state responses at 40 Hz. We found that the OPM sensors have a performance comparable to that of conventional SQUID based MEG sensors, and our results suggest the feasibility of using OPM sensors for functional neuroimaging and brain computer interface applications.

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“…This is common across most OPMs used for MEG measurements: QZFM Gen-2, QuSpin Inc.; and HEDscan™, Fieldline Inc. (but see Limes et al. (2020) and Kowalczyk et al. (2021) for alternative SERF-free OPM designs).…”

Section: Hardware For Opm Interference Suppressionmentioning

confidence: 99%

“…The internal coils can theoretically achieve field nulling up to fields of ±50 nT, but in reality, measurement non-linearities are introduced into the data at around ±5 nT. It should be noted that closed-loop OPM systems are developing fast ( Fourcault et al., 2021 ; Kowalczyk et al., 2021 ; Sheng et al., 2017 ) and are already commercially available with a dynamic range of 200 nT and closed-loop 3dB bandwidth up to 300 Hz (e.g. HEDscan™, Fieldline Inc.).…”

Section: Hardware For Opm Interference Suppressionmentioning

confidence: 99%

Interference suppression techniques for OPM-based MEG: Opportunities and challenges

et al. 2022

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One of the primary technical challenges facing magnetoencephalography (MEG) is that the magnitude of neuromagnetic fields is several orders of magnitude lower than interfering signals. Recently, a new type of sensor has been developed – the optically pumped magnetometer (OPM). These sensors can be placed directly on the scalp and move with the head during participant movement, making them wearable. This opens up a range of exciting experimental and clinical opportunities for OPM-based MEG experiments, including paediatric studies, and the incorporation of naturalistic movements into neuroimaging paradigms. However, OPMs face some unique challenges in terms of interference suppression, especially in situations involving mobile participants, and when OPMs are integrated with electrical equipment required for naturalistic paradigms, such as motion capture systems. Here we briefly review various hardware solutions for OPM interference suppression. We then outline several signal processing strategies aimed at increasing the signal from neuromagnetic sources. These include regression-based strategies, temporal filtering and spatial filtering approaches. The focus is on the practical application of these signal processing algorithms to OPM data. In a similar vein, we include two worked-through experiments using OPM data collected from a whole-head sensor array. These tutorial-style examples illustrate how the steps for suppressing external interference can be implemented, including the associated data and code so that researchers can try the pipelines for themselves. With the popularity of OPM-based MEG rising, there will be an increasing need to deal with interference suppression. We hope this practical paper provides a resource for OPM-based MEG researchers to build upon.

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Detection of human auditory evoked brain signals with a resilient nonlinear optically pumped magnetometer

Cited by 24 publications

References 24 publications

Using OPMs to measure neural activity in standing, mobile participants

Using OPMs to measure neural activity in standing, mobile participants

Detection of the 40-Hz Auditory Steady-state Response with Optically Pumped Magnetometers

Interference suppression techniques for OPM-based MEG: Opportunities and challenges

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